Brandon Sullivan's Severe Weather Blog!

2/12/12 - 2/13/12 South Plains Winter Precipitation Event

2012-02-11T22:54:00.000-06:00

A difficult forecast is on tap for the southern plains as a winter precipitation event is expected to unfold tomorrow evening into the morning hours on Monday.

A piece of energy in the southwest US will continue to move eastward and will lead to weak cyclogenesis and return flow across much of the southern plains. Moisture advection will begin in earnest by Sunday evening as a nocturnal low level jet on the order or 50+ kts gets going in full force.

5PM Sunday WRF Forecast - Norman, OK - Note the dry air through the column

The atmosphere will quickly saturate with the low level jet returning moisture into the area Sunday evening. Lift associated with the upper level energy should aid in light precipitation developing across western Oklahoma and Texas by Sunday evening before overspreading much of Oklahoma and into areas of Arkansas and Missouri in the pre dawn hours Monday.


1AM Monday WRF Forecast - Norman, OK - Note the column now saturated with the model generating light to moderate snow.

SREF Forecast - Notice the spread in members

There is a rather wide spread in the SREF members, not only in the surface temperatures, but also the effect of the temperature advection in the low levels. The overall wind and jet structure (at least to me) seems rather anomalous to ordinary winter storms.

At this time it appears that the best potential for significant snowfall (significant with respect to 2011-2012 winter season) will lie across far northeast portions of Oklahoma, and portions of southwest Missouri. These ares will be under less influence of warm air advection and will likely see a longer period of snow accumulations than other areas.


12.00z NAM forecast showing Warm Air Advection taking place Monday in the early morning/pre dawn hours.

Although the event will ultimately come down to short term forecasting and analysis, the models are in a decent consensus at the moment about the overall setup and evolution, but very small differences in thermal profiles (totally inside the range of uncertainty in this model range) preclude greater certainty in the event.

Taking the NAM with a grain of salt, and using its forecast, I would expect precipitation to begin by late evening Sunday evening, likely starting in the form of sleet or snow before transitioning to all snow through the early hours Monday. By Monday morning, precip will switch to more of a mixed bag, which is where hazardous travel becomes an issue. The mid levels will continue to warm through the overnight hours, while the surface stays cool, possibly allowing for a few hours of a very light glazing of ice, mainly across central Oklahoma where the best conditions for such an occurence exist. Elsewhere, expect probably a 1-2 inch snowfall across much of Oklahoma west of I35 with 2-3 east of 35 and north of I40. Higher amounts of 3-5 inches may be found in portions of far northeast Oklahoma and southwest Missouri but these will likely be isolated.

NAM Snowfall Forecast

Well, we will see where this forecast leads us!
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Fall Severe Weather Event (11/7/11)

2011-11-07T02:22:00.002-06:00

Well, it's been a long time since I have made a good blog post on here about severe weather (May 19th). That said, a decent severe event appears possible later today, and the time of year and magnitude of the potential threat is worthy of a post as we approach the event.

Abundant fall moisture has already made it to central TX and will continue to advect northward in the overnight hours, ahead of a large storm system digging into the desert southwest. Weak cyclogenesis at the surface will help to sharpen a retreating dryline across central OK and TX. Increasing ascent inside the moisture and warm air advection wing may help to foster renewed convective development through the overnight hours across Oklahoma and Texas. This presents the first complication to the severe weather forecast tomorrow afternoon. The atmospheric composition in the lowest 3-5 kilometers does not favor a substantial capping inversion that is typical of spring and summer setups. While sometimes problematic, these inversions play a key part in helping the atmosphere recover from overnight or morning convection, often before focus for ascent and afternoon thunderstorms arrives. In a nutshell, the evolution of storm, storm mode, and tornado potential is quite uncertain.

Briefly putting those concerns aside, the overall synoptic setup appears quite favorable for a fall severe weather event. A deep trough is digging into the desert southwest, and phasing energy from a subtropical jet will overspread the forecast area, creating a very strong wind profile. Increasing ascent and favorable placement in the left exit region of the southern stream jet will lead to increasing cyclogenesis at the surface, which will locally back and enhance wind fields, and also sharpen a retreating dryline. This convergence zone should serve as the focal point for initial convective initiation and I would imagine this to be somewhere near Cromwell to Quanah, TX.

Once convection initiation occurs, likely (and hopefully) by 2-4 PM, storms will have a very good environment to work in to produce tornadoes and very large hail, although contingent upon clearing and destabilization being able to occur. Very steep low level lapse rates on the order 7-9 C/KM and impressive shear profiles, will be favorable for large hail, some of which could be quite large. This notion is further supported by cool temperatures in the mid and upper levels, in addition to dry air in the low levels to aid in hail growth. 50-60kt of 0-6km shear will yield an environment very favorable initial modal supercells. High resolution short term models are consistently developing storms west of Wichita Falls, TX along the red river.

Re visiting the idea of morning convection, a number of high resolution short term numerical model guidance, in addition to a look at current mesoscale trends indicate increasing potential for a convection free morning across the target area. The mentioned models seem to have a pretty good handle on these current trends.

Should morning convection clear as forecast, and barring a significant change overnight. I would estimate our preliminary target be centered somewhere around Vernon, TX by 2pm.

Take a look at the images and captions below

Current Surface Analysis (2am)

CAPE Values at 20z Monday

Mid 60 Dew Points

Impressive 0 - 3 KM Lapse Rates. Good for hail and tornadogenesis.

Super High Resolution Forecast Reflectivity at 20z Monday.

Significant Severe Weather Outbreak Today (May 19th, 2011)

2011-05-19T08:45:00.001-05:00

Synopsis: At 12z an organizing surface low across was found in the Texas panhandle. From this low, a dryline was extending southward through the panhandle of TX, while a warm front arches north through central KS then southeastward through southeast KS. North of this warm front, thunderstorms were ongoing, in response to increasing large scale ascent and in response to a increasing low level jet overnight. In the upper levels, a breaking down omega block pattern is seen, with a dominant 70-90 kt jet streak and main upper level energy sitting across the desert southwest. Moisture return is well underway, with mid 60 dew points already into south central KS.

Forecast: The aforementioned surface features should continue to move northward, and the dryline will sharpen across central and southern KS through OK. The warm front will continue to move northward on the heels of ongoing convection, and destabilization should continue to occur in the warm sector. Thunderstorms will likely develop first across central KS in response to increasing convergence along the stationary dryline, and approaching large scale ascent approaching from the southwest. Storms may form further to the south across central OK into TX, but the environment will not be as conducive to development, as it is well displaced from upper level support, and should remain capped for a good portion of the day.

Mesoscale Environment: Once storms initiate across the target area, a potent thermodynamic and kinematic setting could provide the neccesary components for tornadic supercells. Shear vectors perpendicular to the dryline should allow for discrete supercell storms to develop and move eastward. 0 - 1 KM SRH values appear favorable for significant low level rotation, in the presence of impressive SBCAPE as well as favorable 0-3 KM CAPE and Steepening low level lapse rates, which support vigorous rotating updrafts. Favorable wind profiles and storm motions should hopefully keep storms from going through a large amount of interactions/mergers.

Targeting: Eyeballing two places right now. One would be further north into northern KS, near the triple point. Another potential target area is further south along the dryline across southern KS. Leaning toward the northern target right now, where low level wind fields strengthening towards evening could provide favorable for strong tornadoes. Prelim target near Ellsworth, KS at this time, with a secondary starting area around Great Bend, KS

4/3/11 Rapid Supercell Development (Post Analysis)

2011-04-04T12:43:00.000-05:00

I chased yesterday in Eastern Iowa along with my friend and business partner Brett Wright.. I can't really say just how amazing the supercell we were on really was!! It was the most rapid development I have ever seen... My pictures from the day may be found on my website (www.wickedwindmedia.com) or HERE. This blog post will mainly focus on an analysis on the environment conducive to such rapid development, and a detailed radar analysis of the storms.

A strong capping inversion inhibited severe thunderstorm development for most of the day. Through the afternoon, rapid moisture transport continued, bringing low to mid 60 dewpoints all the way into southern Iowa.. Some locations in Iowa also broke record high temperatures for the day! HRRR and other high resolution short term convection allowing models were consistent on the timing and location of supercell development through the day. By 5PM (22z UTC) initiation was looking increasingly likely. Strong height falls over Nebraska were moving east, in addition to strong vorticity advection, and other focusing mechanisms in the mid levels. At the surface substantial instability had developed, with 22z analysis data indicating 2000+ MLCAPE values with little remaining cap. Extreme low level lapse rates on the order of 8c/km were also in place to fuel explosive severe thunderstorm development. Impressive shear values favored rotating thunderstorms, so the show was on.

Below are some analysis images roughly an hour before initiation.


500mb map showing the focus point for convection across eastern Iowa, in the left exit region of a strong mid level jet streak.


Mid Level Height Falls.

988 SFC Low Across Iowa


22z MLCAPE Values showing CINH completely eroded and impressive instability in place.


Impressive Low Level Lapse rates and 0-3KM CAPE values. These impressive values added to the potential for explosive development!

__________________________________________________________________________________

The radar images below from the Davenport, IA Radar show this storms rapid intensification. All of these images take up only 23 minutes... 541pm through 604pm.. WOW

Just weak echoes.

BOOM

The storm has a 3.32 hail marker at this time!


This image shows Base Reflectivity, Probability of Severe Hail, VIL (Vertically Integrated Liquid), and Storm Relative Velocity Data.

_________________________________________________________________________________

These images include 3D and 2D views of the storm, showing its amazing strength.

Very Impressive reflectivity levels to 40kft. Indicative of very large hail potential!

The Feb 27th 2011 Chase

2011-02-28T11:19:00.000-06:00

What a great chase yesterday afternoon in Southern KS and Northern, OK.. A perfect target that allowed us to play sit and wait for initiation made it a fun and enjoyable afternoon with friends. Once the storm started we were in the prime position, and stayed with the storm until finally catching a brief tornado before leaving the storm as it continued east.

Myself and chase partner Brett Wright started the day in Pond Creek, OK just north of Enid, OK. We went east toward Blackwell, OK to meet with some fellow chasers, before heading back west once storms initiated.

In a short synopsis, we were looking for the potential of supercells to develop along an approaching dryline. A strong warm layer of air was expected by many to hold storms from firing, but we definitely saw a distinct potential for it to break, and we weren't going to miss an event!

At 19z the radar was quiet, except for a few storms that had fired along and north of the warm front in south central KS... We anticipated these storms to enhance the warm front to the south, and this furthered our hopes for a good day!

19z Radar Map

At this same time, analysis showed moisture convergence, and positive vorticity advection along the dry line, we expected this to help provide the fuel for severe storm development, as it shortly thereafter did.

19z Moisture Convergence

19z Vorticity and Vorticity Advection

By 21z (3pm) significant instability was in place to support thunderstorm development.. Clouds had eroded along the dryline, allowing for rapid destabilization.

21z MUCAPE Values

Not long after, thunderstorms ignited off the dryline in western OK.. Two storms formed, and the call was which storm to go toward.. Our initial gut told us to wait for the southern storm, as its trajectory would most likely take it near the warm frontal boundary, where we hoped for favorable interaction with that boundary, and a tornado!

2210z Radar Map

Another issue arose during the chase.. The moisture had seemingly mixed out pretty well through the afternoon hours.. Mesoscale analysis indicated the best moisture was toward the east, near I35. With the mess of chasers out there, we had to make the right moves, to avoid them, while still monitoring the storm, but not making the choice to get in and under the storm until later, as it moved into better moisture.

21z Dewpoint and Low Level Lapse Rates.
(Note the best moisture toward the east)

Now the chase began... The rest of this post is mainly pictures... Just read the captions to know what is going on!

Storm has initiated.. We are playing sit and wait, and getting a a good view of the storm.

View at time of radar image above.

Brett watching the updraft continue to grow
(Notice how tilted it is, from the strong shear)

The storm as it is ready to cross I35.. This is taken from the Blackwell, OK exit on I35..
(Note the well defined wall cloud below.. Rapid rotation was evident at this time)

Another radar grab... We are the circle with the dot

This image below is where we made the wrong call... The storm was/had just split, and was still moving to the northeast... As you can see from the road map, we could either go north or south.... I chose to go north, and many followed us, but as soon as we did, the storm seemed to jog back to the right a little bit...

We are leading the chaser parade!

We head east, and then back north.. Still a nice lowering at this time.

The lowering from the image above passed directly over us, as the road options get pretty grim in Osage county, OK... As it passed, we saw multiple funnels and many impressive funnels, and finally it produced a low contrast (from our angle) tornado to the east. We could barely see the dust/debris due to the poor lighting behind the storm, but time stamp collaboration with fellow chasers, (who apparently went right, and came up under it from the south) confirms we saw our first tornado of 2011!

Photo of the large cone funnel... Some dirt/debris is evident as we get on a flat plane, just up the road.

After that, we called the chase off.. As it was getting dark, and the storm was racing east... We saw some awesome hail fog, and collected some hail that was still scattered about! All in all, a great day, succesfull, and very well executed.

Hail Fog!

Hail!

Severe Weather Threat (Thursday Feb 24th, 2011)

2011-02-23T23:04:00.000-06:00

You know, my thoughts on what I plan to do tomorrow are rather simple.. Most Hi Res short term numerical guidance continues to tell me to play on the low, across eastern/northeastern OK and hope for any enhanced warm front interactions.. This is where the models show the most instability, where the region sits in enhanced low level lapse rates. Im hoping there are some more mesoscale effects, and some locally backed winds, but we will find that out tomorrow.

Im having a hard time getting excited about playing what I feel like will be a damaging wind event, in the afternoon and evening across Arkansas.. Sub cloud instability is a little better with the 00z models, but still nothing to write home about. VWP's and PWAT values just scream line with HP's to me.. With a setup like Sunday on the horizon, my desire to go all out for that risk is low.

4km WRF from 12z today and 00z show a few discrete cells breaking out in the vicinity of the low, which makes sense to me.

I am not hopeful for tornadoes anywhere tomorrow, especially my target in northeast/east oklahoma.. But I would like to see a nice supercell like the WRF indicates.

http://www.emc.ncep.noaa.gov/mmb/mpy...0/refc_f22.gif

http://www.emc.ncep.noaa.gov/mmb/mpy...mxuphl_f22.gif

http://wxcaster4.com/nam/CONUS_ETA21...IGSVR_21HR.gif

Winter Storm Watch "Imminent"

2011-01-29T15:47:00.000-06:00

Well, barring any sudden model forecast changes, it looks like Central OK is in for quite the winter storm! I'm currently on my way to Chicago, so I will post a more detailed forecast tomorrow.. In the mean time, take a look at this text from the National Weather Service in Norman, OK..

WINTER STORM WATCH IS INEVITIBLE BUT WE WILL  
HOLD OFF FOR NOW DUE TO THE WORST OF THE EVENT LIKELY UNFOLDING IN  
PERIODS 5/6. STILL MANY VARIABLES AND UNCERTAINTIES REGARDING  
PRECIP TYPE AND AMOUNTS - ANOTHER REASON WE ARE HOLDING OFF ON  
HEADLINES FOR THE TIME BEING. IT LOOKS LIKE A TRANSITION FROM  
RA/DZ TO ICE TO SNOW WILL BE RATHER SWIFT AS THE COLD AIR POURS IN  
MONDAY NIGHT AND TUESDAY MORNING. LARGE-SCALE PATTERN FAVORS HEAVY  
SNOW SOMEWHERE ACROSS THE AREA BUT TRACK OF UPPER SYSTEM IS  
UNCERTAIN AND THEREFORE SO IS THE LOCATION OF THE HEAVIEST  
ACCUMULATIONS. STRONG WINDS LEADING TO BLOWING/DRIFTING SNOW AND  
POSSIBLY BLIZZARD OR NEAR-BLIZZARD CONDITIONS SOME AREAS BY  
TUESDAY... AND DANGEROUS WIND CHILLS -10 TO -20 BY WED MORNING.

St.Louis

2011-01-16T20:59:00.001-06:00

Well, I went to sleep about 5am this morning in Oklahoma.. woke up at 7, to fly to Chicago.. Had some lunch and a meeting. Now I'm headed back to Norman with a friend who lives near Chicago! Will be a long drive but good fun! Hope I can catch up on sleep before classes start Tuesday!

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Happy New Year!!!!

2011-01-01T00:17:00.001-06:00

Happy new year!! Oklahoma style celebrating!!!

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Headed back to Illinois!!

2010-12-20T13:11:00.001-06:00

Look, its snow!! Haven't seen that in about a year! High is 71 back in Norman today, can't deny I wouldn't like to be there, but it will nice being home for the holidays!

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11/24/10 (OK/MO) Severe Weather Post-Analysis

2010-11-25T00:59:00.002-06:00

A lot of chasers ventured out today, anxious for a late season tornado catch! A powerful upper level system, combined with a unseasonably warm air mass was expected to set the stage for supercell thunderstorms with the potential for tornadoes across Oklahoma, Arkansas and Missouri. At the end of the day,only one tornado has been reported, although a few supercells were spotted. Let's dig a little further and see what happened today.

General Synoptic Setup
The large scale synoptic pattern featured a strong positive tilt trough centered across the western US. This set the stage for strong southwesterly flow in the mid and upper levels. At the surface, low pressure was deepening across far western Kansas and Colorado. A stationary boundary was located across Texas early in the period, and was lifted northward as a warm front through the day in response to the aforementioned deepening low pressure. To the south of this boundary, temperatures rose into the mid 70's by afternoon. Thunderstorms were expected to develop along and especially ahead of the encroaching cold front, amidst increasing large scale forcing and a moderately unstable environment, owing to a unseasonably moist airmass in place, with dew points rising into the mid 60's by afternoon.

By Early Afternoon...
By 18z, special soundings from NWS Springfield, MO and the NWS Norman, OK gave a slightly better insight into the atmosphere. The Norman, OK sounding showed an unstable environment, where only some mid level clouds had persisted through early afternoon. The Springfield, MO sounding however, shows a very stable environment. It appears as though the warm front has just passed through Springfiield from this sounding, but the true warm air had yet to reach the area. Both soundings exhibit impressive deep layer shear values, with 88kts on the Springfield sounding!! Although the Springfield sounding showed a lack of appreciable instability, continued clearing along and south the warm front would continue to aid in destabilization, especially in the mid levels in the afternoon hours. At 19z low and mid level clouds were still persisting across all of eastern Oklahoma, with the main breaks in the clouds now occurring across extreme northeast Oklahoma, and along I-44 through central Missouri. In addition, higher clouds were still evident across central Oklahoma.

The 18z run of the HRRR ( High Resolution Rapid Refresh) pegged a few thunderstorms to develop around 22z along the I44 corridor in far northeast Oklahoma into southwest and central Missouri. With recent satellite trends, showing maximized destabilization potential over that area, this made sense. By 22z severe thunderstorms were already ongoing across far southeast Kansas into central Missouri. In the presence of strong low level shear, these storms briefly exhibited increased low level rotation, but no tornadoes were reported. A quick look through mesoanalysis data, and radar information as the event unfolded, shows that although storms were semi organized they were likely not surface based. A stable low level atmosphere kept the storms from tapping into the available moisture at the surface. 0-3km CAPE values however were indicative of sufficient instability to support strong thunderstorms updrafts. In the presence of the strong shear, any storm that was able to realize this mid level instability and sustain itself for a period of time, was able to take on supercell characteristics, as seen across southwestern Missouri. One storm in particular near Brighton, MO was able to produce a brief EF-1 tornado that caused some minor farm damage. This storm exhibited very strong low level rotation, and appeared to become surface based for a short time, noted by the wind reports from the storm.

What Went Wrong...
In general, rather meager low level lapse rates, and a lack of surface instability, in the presence of excessive shear, likely prevented a larger scale and more significant event. Morning clouds, and slightly over-forecast moisture values offered less instability than was expected. Those storms that were able to sustain themselves were able to transfer strong mid level winds to the surface, and a few storms in Missouri exhibited strong low level rotation, in the presence of impressive low level shear, and one produced a tornado. Ultimately though, today was characterized by a mainly wind and hail event.The thunderstorms across MO prove that constant analysis of the atmosphere becomes vital, especially with nearby frontal boundaries, that play significant roles in the thermodynamic layout of the atmosphere.

Pertinent Images From Today

11/24/10 12z 500mb Analysis

11/24/10 12z Sfc Analysis

SPC Storm Reports 11/24/10

Norman, OK Special 18z Sounding

Springfield, MO Special 18z Sounding

18z Vis Sat Imagery

(Note the clearing along the I44 Corridor)

22z SBCAPE

22z 0-3km CAPE

(note the MAX near the storms in MO)

18z HRRR 4hr Forecast.. Valid 22Z

Severe Weather to Return to the Southern Plains Tomorrow (Forecast 11/24/10)

2010-11-23T23:59:00.008-06:00

It's November, but believe it or not, we are looking at the threat for a severe thunderstorm event across Oklahoma. Though quick moving storms, and less than favorable terrain may add some challenge to the forecast, the ingredients are coming together for a severe thunderstorm event tomorrow. Lets look into the setup!

Currently, a stationary front is draped across Central Texas into Southern Arkansas. A few elevated showers and storms are occurring on either side of the front, and may continue through the overnight hours. As low pressure deepens across Oklahoma tomorrow, this stationary front will be lifted north as a warm front. In the upper levels a powerful trough will continue to dig into the southern plains, with nearly 80kt of WSW flow at 500mb.. Deep layer shear values 65+ kts will provide more than adequate support for organized thunderstorm activity..

There is some discrepancy between Numerical models in the amount of instability that will be able to develop in the warm sector tomorrow afternoon. Latest High Resolution short term models are less generous with instability across the area, with SBCAPE values less than 500 j/kg across the area.. Morning precipitation and cloud cover likely are the causes for these discrepancies. With the moist airmass in place, any localized clearing would lead to rapid destabilization. If destabilization would fail to occur as the RUC/HRRR suggest, the amount of shear available would probably be "too high" to support powerful long lived updrafts.

Regardless, I would probably start near McAlester, OK as a beginning target..I believe convection should initiate and move rather quickly to the Northeast across the area. I would expect damaging winds to be the primary threat with the upper level energy in place, and freezing levels too high for a large hail threat.. Tornadoes will also be possible, especially in northeast OK into MO, where low level shear will be enhanced..

Forecast and Analysis Images

Current SFC Map 06z 11/24

Current 500mb NAM 21 hr Forecast 21z 11/24

12am Wednesday (11.24) Radar, SFC Obs, Frontal Boundaries

Model Discrepancies - 21z CAPE Values

RUC - Top - Low Instability

NAM - Bottom - Favorable Instability

Allentown, PA Thurs Nov 4th Forecast

2010-11-03T18:36:00.000-05:00

Synopsis: A complex flow pattern exists across the central US, as a trough continues to carve its way eastward toward the area. A moist airmass is being advected northward, in response to an upper level low found in the gulf of Mexico, and further aided by an easterly surface component, from a ridge centered off the coast. This moisture combined with increasing ascent ahead of the approaching upper level energy, will yield a rainy day across the forecast area!

Current 500mb Map
http://w1.spc.woc.noaa.gov/exper/mesoanalysis/s19/500mb/500mb.gif?1288826605859

Current 700mb Map
http://w1.spc.woc.noaa.gov/exper/mesoanalysis/s19/700mb/700mb.gif?1288826623865

Forecast: The atmosphere should saturate from top down in the early overnight hours across the area, as moisture is advected northward across the area. Precip should be ongoing by morning Thursday, and will continue for much of the day, as low pressure deepens, and moves eastward. On the backside of this system, winds will shift to the north, and usher in cooler temperatures. Extensive low clouds and moisture laden air will prevent significant cooling in the overnight hours. With that said, the temperature may reach its minimum near the end of the period, depending on the extent/duration of precip. Here is an image created, that shows the amount of 1hr precip (green bars), clouds (white) and temperature(red) as well as dewpoint (green) . CAPE (red/green/yellow line at bottom) is also plotted here, but as you can see, it is rather negligible. Meaning that there will not likely be any convectively enhanced precip.

http://www.wickedwindmedia.com/KABEOverview.jpg

Thus, looking at tomorrows data, highs should be confined to the mid 40's, as rain and clouds will likely hold temperatures down. Winds will be tricky with the precip, but it should be safe to assume that they will certainly be stronger than the previous few days, with low pressure deepening in the area, and any added momentum transfer from precip loading. This precipitation event should be more of a strati-form rain type event, with little in the way of thunderstorms to yield locally enhanced precipitation amounts. It's likely that much of the area will see over 1/2 inch of precipitation tomorrow. I encourage you to look at the latest model data, to look at the speed and timing of features, in determining the amount of total precip that will fall. Min temperatures, in addition will be tricky. It appears rain may be ongoing during the favored low temperature time frame. This may hold temperatures up slightly in the early morning hours. Models do indicate some cool air behind this system, so depending on when precipitation ends Thursday evening, the low may actually occur, once again, near the end of the period, as seen in the image posted above.

-Brandon Sullivan-
University Of Oklahoma
School Of Meteorolog

Forecast Thoughts for October 21, 2010 (TX/OK)

2010-10-22T00:34:00.000-05:00

One of the first fall severe weather setups is here, and I am headed to Southwest Oklahoma.. There are two synoptically evident areas for severe weather, with the first being across Kansas beneath a cold core upper level low. The second, and more evident, will be across Oklahoma and Texas, and this is where I will find myself. I must note, time constraints restrict my time to the southern target, so my lack of attention to the north target should not be seen as pessimism to the forecast.

Ongoing convection appears to be handled well by some short term models, and the trends suggest that storms should dissipate by late morning, allowing for surface instability to develop tomorrow afternoon. A strong upper level jet, crossing a well defined dryline across western Oklahoma, along with a retreating surface boundary across southern Oklahoma should provide the foci for thunderstorm development by mid afternoon,

Once storms initiate, impressive deep layer shear values aligned against the boundary should promote thunderstorm development, likely in the form of supercells across northern TX and southern OK by mid afternoon. As storms move from the boundary, increasing low level shear below amidst already sizable hodographs will yield increasing tornado potential. Furthermore, steep low and mid level lapse rates will allow for large hail to be a threat also.

In short, definitely a nice fall chase day tomorrow! My team will be leaving Norman by early afternoon headed for SW OK. If data allows, look for updates and live video!

Night Sky Across Oklahoma

2010-10-16T23:15:00.000-05:00

Change of plans tonight which left me with an open evening. Made a solo trip out to take some pictures across the Norman area! I really enjoy getting the stars in there too! Still trying to learn and improve skills and shots, but for now I am just playing with ideal photos, and finding shots worth taking. The RAW files are much less grainy.. Feel free to comment!

Glasgow, MT Day 4 WXChallenge Forecast

2010-10-14T14:57:00.000-05:00

Synopsis: After a bitterly cold start to the morning, temperatures have recovered nicely into the mid 60's with the latest reading from KGGW reporting 67. To the southwest, low to mid 70's have already been observed early afternoon. Strong southerly winds should continue to advect warm, dry air into the area, and allow temperatures to continue their climb into the upper 60's and low 70's across the area by this evening. In the upper levels, a deep trough continues to carve its way eastward across the east coast, as another trough comes onshore into the northwestern US, continuing the amplified pattern across the CONUS.

Short Term (Tonight and Tomorrow): With dry air firmly entrenched over the region, a clear night is expected across much of Montana. Appreciable southerly winds through the evening should prevent temperatures from bottoming out as they did this morning, with some locales reaching into the upper 20's. Expect lows generally to be in the upper 30's across the area. Highs tomorrow should hit the upper 60s into the low 70s. The main forecast challenge during the period will be winds, as the previously mentioned upper level energy moves onshore. As low pressure deepens across Canada, winds will shift to the west northwest behind the associated frontal boundary, and become increasingly strong. The timing of the frontal passage will be key as to the strength of the winds. The 12z model suite is a little faster with the timing of the front. A frontal passage before sunset would allow for the strongest winds to be realized, as very steep low level lapse rates would allow the mixing to occur more efficiently. Even with a frontal passage, dry air again will preclude any precipitation chances across the area.

One word of caution for forecasters: The strength of CAA ( Cold Air Advection ) is rather strong behind this cold front. If the earlier frontal passage were to occur, temperatures would rapidly fall. I am watching for the potential to actually hit the LOW for the period, before 6z Saturday, basically, it may be colder tomorrow night than it will be early tomorrow morning. While it is possible, I would not say it is probable, but something that may be overlooked, and certainly bears watching, as further model guidance becomes available later this afternoon.

WX Challenge University Of OK (Forecast - City 2, Day 2)

2010-10-12T20:11:00.007-05:00

As part of my schooling at the University Of Oklahoma, I am participating in a forecasting competition called the "WxChallenge". This competition is nationwide, and requires the forecasting of the correct wind, temperature (max and min) and precip.

Today, I prepared a brief synopsis and forecast for the target city this week of Glasgow, MT. I have decided to share the information below, and may do this a few more times on my blog! Enjoy

Synopsis: Gusty west winds are prevailing this afternoon in Northeastern MT as high pressure builds in from the Southwest. Temperatures have warmed into the upper 50's across the area, with mid 30's dew points indicating a dry air mass in place. As the aforementioned high pressure builds into the area, a trough will continue to carve its way across the Northern US. To the south a upper level cut off low, and attendant surface low centered over Southern Missouri and Northern Arkansas, will slowly move to the east, sparking severe thunderstorms this afternoon across Louisiana, Arkansas, and Mississippi.

Short Term (Tonight) - A cool and clear night is in store for the region, as clear skies and calm winds allow temperatures to cool into the low to mid 30's. Overnight, winds will calm and shift to the southwest. By mid afternoon Wednesday, temperatures will have warmed into the mid 60's with some upper 60's readings possible across southern portions of Montana. Winds will gradually turn westerly through the day, but with the upper level disturbance well to the east, and high pressure building into the area, winds will be lighter than what has been experienced today. With any appreciable upper level support well east of the area, and a dry air mass in place, no precipitation is expected through the period.

Good Luck!

-Brandon Sullivan-
University Of Oklahoma
School Of Meteorology

Heavy Rain a Major Concern With Hermine

2010-09-07T13:45:00.000-05:00

As Hermine continues to swirl over southern Texas, it is dropping large amounts of rainfall across the deep south. This system is tapping copious amounts of moisture in the lower and upper levels of the atmosphere, allowing it to produce significant amounts of rainfall. As the system continues to slowly drift NNW, then gradually turn to the northeast, it will take the moisture along with it, and continue to drop heavy rain. Amounts in some locations could receive over 8 inches of rainfall, allowing significant flash flooding. Some locations across the deep south have already picked up 4+ inches since the storm first began impacting the region. Strong upper level divergence and a decent low level jet will continue to allow the storm to produce heavy rain through TX, OK and MO.

The threat for tornadoes appears to have lessened, as it appears the storm will be getting sheared apart, and a sufficient amount of instability will not be able to materialize, owing to vast amounts of moisture in the storm. Although areas east of the track may still find a few reports of tornadoes.

Day 1 Precip Forecasts

Day 1 - 3 Precip Forecasts

_____________________________________________________

Current Analysis

Current Surface Map

Current IR Sat Map

500mb Analysis

Tornadoes with Tropical System Landfall

2010-09-07T01:25:00.000-05:00

Tornadoes associated with tropical systems can be difficult to forecast. Tornado coverage and intensity are not always a direct correlation to the strength of the tropical system. Most tropical systems provide the favorable wind fields for low top supercell thunderstorms in the right front quadrant of the system. Moisture is certainly not a factor, and neither is lift. A key factor however is surface instability. This instability allows the updraft strength needed for a thunderstorm updraft to stretch and realize the vorticity available.

When dry air is wrapped into the tropical system, it can provide the clearing and instability needed to promote surface instability.

This wednesday, there appears to be a reservoir of dry air across western Texas. It is unclear how Hermine will interact with this dry air, but should it be ingested into the system, there is substantial supporting factors for tornadic supercells across Oklahoma and Texas.

I would personally suggest reading a brilliant write up / case study by Jon Davies about Hurricane and Tropical Cyclone Tornado Environments

I will likely be chasing Wednesday, so stay tuned!!
Below, I have some posted some current images from Hermine!

TS Hermine Inland. North of Brownsville TX

Remnant Tropical Storm to Impact the South

2010-09-06T20:44:00.000-05:00

Right now Tropical Storm Hermine is turning off the southeast coast of Texas. Latest radar imagery places Hermine about 46 nautical miles South Southeast of Brownsville, TX. Although atmospheric and oceanic conditions would support further strengthening, Hermine is racing quickly on shore. Here are some images associated with Hermine.

Visible Sat and Forecast Path and Strength


IR Sat Image of Hermine


8:28 PM Radar Image

8:28 Base Velocity Image

The Hi Res Radar imagery clearly shows the center of Hermine. There appears to be some banding occuring with the storm, with radar showing max winds of 53kts on the right front quadrant of the storm.

Beyond the immediate impacts of the storm imapcting the south Texas area, additional hazards may include the threat of tornadoes through Wednesday. And heavy rain through Thursday.


3 Day Rainfall Totals

Skew T For Denton, TX at 00z Thursday

Overall, the system will have a variety of impacts. Strong winds and tornadoes will be the inital threats as the storm moves inland, but by mid-week heavy rain and flooding will be the primary concern across central Texas and Oklahoma.

Traffic in Tulsa

2010-08-13T13:18:00.001-05:00

Bout 2 hrs outside of Norman. Traffic is sitting still here in Tulsa.. Probably some big accident ahead... Just ate at a golden corral though. was good. just wanted to do a quick update! Norman by 330 if traffic cooperates!

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Off to Oklahoma!!

2010-08-12T14:51:00.001-05:00

Well I'm off to Oklahoma! Just about Hannibal, MO... Got some nice storms popping up all over so maybe will be lucky enough to see something of note. I'll keep posting to this a lot in the next few weeks as I get settled into Norman!

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National Balloon Classic - Indianola, Iowa

2010-08-02T00:50:00.000-05:00

Most don't know that hot air ballooning is one of my favorite things to do in down time.. I have a number of friends who have hot air balloons and I like to fly with them and help them out. Yesterday I rode with 20 year old pilot Spencer Conlin as we flew high up at the National Balloon Classic in Indianola, Iowa.. There are over 100 balloons here, and it is such an awesome time! I took this video through the event!

Off to Oklahoma Soon!

2010-07-28T23:18:00.001-05:00

Just wanted to test out the mobile posting system... I can post to my blog wirelessly, which then instantly goes to Facebook also..

Headed to Oklahoma the 13th or 14th of August... Lots of packing to do between now and then... That means no more missed huge tornado days in Oklahoma next year!!!!

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Photography Beyond The Weather

2010-06-29T10:41:00.000-05:00

Of recent I have found that tornadoes and clouds or lightning or any weather phenomena don't have to be in my viewfinder to make for a picture that I am happy with. Last night I went for an evening walk around the lake and was able to capture a few cool pictures, and I just wanted to drop in and share them! These are just a few that I took..

My favorite!

University Of Oklahoma!

2010-06-27T17:26:00.000-05:00

Just thought I would drop in and post some info about the University and the apartments I will probably be in!

The weather affects everyone. Meteorologists have the knowledge to warn people of severe weather such as tornados or hurricanes and possibly save hundreds of lives. Meteorologists observe, predict and study the weather. OU houses the nation's largest meteorology school and is the only U.S. school to offer a Professional Meteorology master's degree. The nationally ranked School of Meteorology gives students the opportunity to learn the skills needed to work in one the fastest-growing and most-influential career fields.

Live like you mean it at University Greens, the best in Norman student living! At University Greens you will have the privacy and lifestyle you deserve in an off campus student community that is built specifically with you, the college student, in mind.

Take advantage of our convenient location and unmatched amenities—everything you want and need in one place makes University Greens the best in college apartments! University Greens is located within walking distance of The University of Oklahoma in Norman, OK, has a private shuttle to campus, and is within walking distance of the Campus Corner. You will also enjoy our amenities including a 24-hour fitness center, basketball court, sand volleyball court, swimming pool with hot tub and sun deck, and much more.

University Greens also offers fully furnished student apartments in a variety of floor plans to choose from, individual liability leases, and cable and internet are included. Electricity is also included up to a monthly cap.

Illinois Tornado Outbreak June 5th 2010 : An Analysis and Overview

2010-06-06T18:13:00.017-05:00

June 5th, 2010 Tornadoes Across Illinois

06/05/10 Storm Reports

The tornadoes of Saturday June 5th, 2010 came largely as a surprise to many chasers including myself. Although the lead time for any individual storm was immense, the overall evolution of the severe weather scenario differed from the expected course of events. The purpose of this article is to analyze the event in retrospect in an attempt to improve real time situational awareness.

The morning analysis featured a 1002mb low across southwest Kansas. Multiple boundaries were found across the upper Midwest. The first residual boundary was located across northern Iowa and draped across northern Illinois where convection developed and maintained itself. The main warm front was analyzed across the Missouri border and was reinforced by convection to the north of the boundary.

12z SFC Analysis

The ongoing convection in the morning would come to play a role in the afternoon convection location and intensity. The aforementioned boundaries were easily visible in the below Composite Reflectivity image.

1310z Composite Reflectivity Image

The general upper air pattern featured a moderately strong western zonal flow. Seen below is the 500mb analysis featuring a 70-90kt jet core punching into central and northern Iowa.

12z 500mb Heights, Temps and Wind (Kt)

The Storm Prediction Center had issued a Moderate Risk for Severe Thunderstorms across eastern Iowa and central Illinois eastward into Indiana into Ohio. Convective initiation was expected to become increasingly likely along and ahead of a cold front in central Iowa. The kinematic and thermodynamic profiles that would support this moderate risk will be mentioned later in this article.

Morning SPC Overview

Model Guidance Before The Event

The synoptic setup of the 5th featured a westerly zonal flow across the midwest. In these setups, West to East oriented fronts become the focal point for convection to ride eastward in the evening into the overnight hours. These convective systems become a crucial factor in the timing, location of development and intensity of convection the following days. Remnant boundaries and convective debris can play a significant role in the development of severe weather, and in many cases can act to minimize the threat. Due to the compelexities of model handling of convective evolution 20+ hours out from the event, the reliance on forecast models falls second to the importance of close analysis and short term forecasting the day of the event. For this reason only a general overview of various model guidance will be provided in this examination.

Synoptic Evolution

Below are images from 12z, 15z, 18z, 21z and 00z. To these images I have inserted fronts and other boundaries as I have interpreted them. These five images should help better show the evolution of the storm system.

12z Surface Analysis

15z Surface Analysis

18z Surface Analysis

21z Surface Analysis

0z Analysis

Chasing Today in Northeast Colorado!

2010-05-21T10:09:00.000-05:00

A great setup looming today in northeast Colorado between the Cheyenne Ridge and the Palmer Divide!

Looks like by late afternoon into the evening the cap will erode and upslope flow will allow the development of discrete supercell thunderstorms east of Denver.. The 4km WRF is definitely on board with this, and shows 3 discrete supercells across the area!

Long story short, enough instability, combined with favorable wind shear, should yield some nice shots later today! I am pretty stoked about the potential for beautiful supercells and some tornadoes..

Severe Weather Outbreak Tomorrow In Oklahoma!

2010-05-18T22:27:00.000-05:00

After an active severe weather evening across Colorado and Texas, another interesting severe weather event is shaping up for tomorrow afternoon.

By Mid Afternoon Thursday a sharp dryline will be found across western Oklahoma southward into central Texas.. Surface dewpoints of 65+ will be found along the moist side of the boundary. To the north a warm front will likely be draped across the KS/OK border, but the exact location will ultimately be a result of morning convection ongoing from tonight.

In the mid levels, a 500mb jet streak will be found crossing the dryline bulge, with the left exit region of mid level jet co located across the region.

Convergence along the boundary and a well timed shortwave should ignite convection across the northern part of the dryline by late afternoon. Shear values of 60+ kts with vectors perpendicular to the boundary should yield discrete storm activity. Kinematic and instability profiles will largely be supportive of supercells with VERY large hail possible, owing to steep low and mid level lapse rates and dry air in the mid levels.

Along the boundary, tornadoes are a good threat, due to enhanced low level shear and deep moisture in place. As the evening draws closer, an increasing low level jet feature will also aid in the tornado threat.

Initial Target : Watonga, OK

Dew Point Forecast

500mb Wind/Height Forecast

Sounding From Watonga, OK @ 00z Thurs

Might post another forecast in the morning, or while on the road.. On the road right now, hence the lack of more detail.

-Brandon

Severe Weather Possible Again 5/12/10

2010-05-12T00:38:00.000-05:00

A somewhat less broadcast, but still decent severe threat exists across portions of Oklahoma, Kansas, Missouri and Illinois tomorrow afternoon.

A large upper level trough will begin to lift out of the plains Wednesday afternoon. As this happens a surface low pressure system will move eastward across Misourri.

The first forecast challenge revolves around the eventual location of the warm front. Currently, MCS formation is occuring over Kansas. Overnight, this MCS will translate eastward across the warm front. Ultimately, this may act to limit the northward progression of the warm front tomorrow afternoon..

The next forecast challenge is the forecast capping inversion that should limit convective development for much of the day.

During the late afternoon, indications of a subtle mid level shortwave, combined with upper level divergence from an upper level jet speed maxima, may provide just enough to fuel thunderstorm development.

If thunderstorms develop, the post frontal environment features high CAPE values owing to significant moisture transport, and diurnal heating. 0-6KM shear values of 60+ KTS will be favorable for supercell thunderstorms..

At this time I would anticipate heading into Misourri during the late afternoon and evening.. With so much uncertainty however, I will wait before making any real target.

Overview of 5/10/10 Tornado Outbreak

2010-05-10T22:50:00.003-05:00

A significant severe weather outbreak occurred today across portions of Kansas, Oklahoma and Texas. Numerous significant tornadoes have been reported with significant damage being noted across many areas. I would like to discuss in better detail below, the setup that lead to such an event.

To do a sort of top down approach we see that a strong upper level trough was located across the area, with the KS/OK region lying underneath a zone of divergence.

H25 Shows a Deep, Powerful Trough.

500mb was characterized by ~60-70 KTS flow.. With the region under the favorable exit region of the mid level jet axis.

Cold Air advection was also occuring in the mid levels, most notable at H5. This helps enhance updraft strength and enhance vertical vorticity.

As we approach 700mb we see a shortwave rounding the base of the trough that would contribute to storm development in the afternoon hours.

850 shows an impressive low level jet advecting copius moisture into the target area.

At the surface, extreme instability developed rapidly in the wake of morning convection. The pre dryline environment was characterized by 65 degree dewpoints and southerly surface winds. In a theta e rich environment, and impressive wind fields the atmosphere was primed for supercell development.

A special 20z Sounding from KOUN showed an impressive environment conducive for significant severe weather.

* Note the strong veering wind profile, and impressive upper atmospheric support. CAPE values approaching 4000 J/KG.. Cold air advection @ mid levels.. Dry Air @700mb.

Ahead of the dryline, strong forcing and upper air support aided in the development of supercell thunderstorms. Along the OK/KS border supercells developed first, and quickly went tornadic.

Further south along the dryline, more supercell storms erupted later as the previously mentioned shortwave passed through the area. Incredible low level storm relative helicity promoted enhanced low level rotation. This combined with sufficient low level moisture served to enhance the tornado threat. Shear vectors perpendicular to the boundary kept supercells discrete for an extended period of time.

Here is a radar grab from the supercell that produced significant damage in the Oklahoma City/Norman area!

In closing, an incredible combination of impressive wind fields at all levels, combined with sufficient forcing, and upper support for thunderstorm development, and a moisture laden, theta e rich surface environment, combined for a potent outbreak of tornadic supercells that caused significant damage in some locales.

Situation Update: 5/10/10 KS/OK 19z

2010-05-10T14:09:00.000-05:00

Extreme instability is developing as forecast along and south of the warm front as it surges to the north. The pre dryline environment is appearing very favorable for supercell development in the next few hours across central and northern Oklahoma, where 64-66 degree Td's have made it across the region. The region lies under the left exit region of a strong upper level jet, associated UA divergence, combined with impressive forcing and increasing moisture convergence should ignite storms in the next few hours in central Oklahoma..

Impressive shear values with shear vectors aligned perpendicular to the dryline should promote discrete supercell development. Low level features and upper level wind fields are favorable for strong tornadoes. The tornadic threat may increase even more after initiation however.. Storm motions of 50kts could support the threat for long track tornadoes.. In addition, impressive low/mid level lapse rates should favor very large hail across the area with any supercell.

A PDS Tornado has been issued.

Expect continued development in the next few hours.

Severe Thunderstorm Outbreak Still Appearing Likely! 5/10/10

2010-05-10T11:25:00.001-05:00

Well it appears as though in reality the NAM did verify from last night in that it holds the warm front well to the south..1515 satellite imagery shows clouds still draped over the area which has served to limit destabilization thus far today.

RUC Guidance however that impressive rapid destabilization will occur south of the warm front this afternoon, in a theta e rich environment.. CAPE values upwards of 3000 J/KG should be found across the risk area by late this afternoon!

A shortwave rounding the base of the upper level trough should ignite supercell thunderstorms along the boundary during the afternoon. Shear vectors perpendicular to the dryline, and impressive deep layer shear values should promote discrete supercell activity.

The threats from these supercells include very large hail owing to impressive low and mid level lapse rates, and strong tornadoes. The threat for strong tornadoes exists due to impressive helicity values in the warm sector in the pre dryline environment. Impressive wind fields will also promote rapid storm movement to the ENE, thus the threat for long track tornadoes exists as well.

My target as of right now would be Tonkawa, OK..

Severe Weather Outbreak Today Across KS/OK (5/10/10)

2010-05-10T00:48:00.002-05:00

A potent severe weather situation is setting up in the nest 24 hours across portions of Oklahoma and Kansas.

The synoptic setup will feature a shortwave trough over the four corner regions that will advance eastward through the MO valley. A strong upper level trough will be found across the region with 70-80 KT westerly H5 flow to be found across the southern portions of the target area.. At the surface a ~996mb low will be found across southwestern KS near DDC by 21z Monday.

Morning convection should be ongoing at the start of the morning period in response to a strong low level jet and associated deep moisture transport, these storms should be mainly elevated capable of hail as they move off to the northeast, on the eastern periphery of a translating elevated mixed layer.

In the wake of morning convection, models show rapid destabilization occurring in response to increasing theta e transport downstream of a H5 vorticity maximum, and impressive cold advection in the mid levels. >65Td's should be well established by mid afternoon in the pre dry line environment.

Upper level divergence associated with the left exit region of mid level jet, aided by impressive forcing and diurnal heating and instability should spark a few isolated supercells on the northern edge of the dryline, immediately east of the surface low, across southern and central Kansas. Here, low and mid level wind profiles favor strong supercell potential, in a region characterized by 50kts 0-6 KM Deep layer shear below impressive H5 jet streak and ~90kt H25 flow.

Further south along the dryline into central Oklahoma, development will be more contingent upon the shortwave progged to cross the region in the late afternoon hours. In this region, impressive shear values and incredibly steep lapse rates will favor supercells with extremely large hail, and the potential for strong tornadoes. LCL levels of >700m will be found across the dryline. In addition, storm motions of 45-55 MPH will lead to the potential for long track tornadoes as well.

At this time my preliminary target area would be very near Wichita, KS..