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Meteorologist Ted Keller posted this in Forecast Discussion, Storm Chase Discussion, Storm Chasing on May 19th, 2010
It does looking increasingly likely that I will be heading out on a storm chase Saturday. Target area from this vantage point would be western Kansas northward into extreme southern South Dakota. Now, this event is 84 hours out to I expect to adjust this area several times of course.
The overall set up is a large trough in the western U.S. this weekend and an abundance of moisture and instability. Most of the impressive instability will likely be capped over much of the Great Plains. All hinges on whether the jet stream can infringe enough eastward into the instability. Shortwave features will play a role in dryline maintenance and movement. The flow is a bit meridional too but this may be resolved somewhat by as yet unseen shortwave features.
Many of you know I am offering opportunities to storm chase in a short-fuse, weekend type situation. Please look on the Ceaseless Wind website if you are interested! If you have a desire to do this but are unsure of some things, e-mail me ted@ceaselesswind.com and we can talk about it in private.
Also, don’t forget about “Upstream”, my live web show at 6:30 tonight and every weeknight. We will likely have ongoing severe storms to discuss in Oklahoma and I will also be updating the weekend chase situation as well.
 Severe Outlook for Monday This has been holding together for a few days now in the computer model forecasts so confidence is running higher that an outbreak of storms will occur over the central Great Plains Monday.
There has been some fluctuation in the position of the dry line which defines the western edge of the threat area, If it ends up over central portions of Oklahoma and Kansas, the Ozarks would see whatever supercell thunderstorms do develop move into the area later that evening.
One computer model (NAM) from 12z Friday has pushed the dryline back westward after trending more east the past few runs. The GFS model is sticking with an “I-35″ (or thereabout) solution which is more east.
Since the event is still 78-84 hours away, there will likely be more adjusting of the position east or west.
The differences are arising because the speed and position of the shortwave trough are radically different between the NAM and GFS computer model! I posted the images below. This will make a HUGE difference in where the threat area ends up! This position will shore up as soon as we get closer to Monday and the shortwave “comes ashore” to be sampled better by upper air measurements.
My friends Matt Gingery and Jill Gilardi will be out chasing on a special project starting Monday. What a way to kick things off! I wish them luck and safe travels!
I will be doing a special “Upstream” broadcast on Sunday evening, most likely after the 00z NAM comes out which will be after 9 pm sometime. I’ll keep you posted!
 NAM 500 mb 7pm MondayGFS 500mb at 7pm Monday
Meteorologist Ted Keller posted this in Forecast Discussion, Severe Storms, Storm Chase Discussion on May 1st, 2010
 High Risk Today! The southeastern U.S. has taken a beating with the storms last Saturday and last night. Now, another high risk has been posted for the area pictured.
There is a tremendous amount of moisture as measured by the dew points (colored areas) on the inserted map. This is poised and ready in the high risk area. What will likely happen is an increase in south to southeasterly wind flow near the surface later this afternoon and evening. Another jet stream “max” is coming up out of Texas which will help with the development of a low pressure area over the western portion of the threat area. The winds should respond to this feature.
The computer models have been showing this for a few days but with slightly different results. The GFS has always been more aggressive with the low development. The morning run of the NAM has come around on the winds a bit more. This model is also forecasting 0-3km SRH of 150-300 at 21z (4pm), jumping to 300-350 by 7 pm with these values then expanding over all of eastern Arkansas by after dark. CAPE is progged at over 2000.
 The ongoing cells are likely to been producing severe weather by just after noon in some areas. This is not the main show! This is expected by early evening over the high risk area.
I will be out with the Mobile Weather Lab today. I’ll cross my fingers on live streaming on Severe Studios.
Meteorologist Ted Keller posted this in Storm Chase Discussion on April 28th, 2010
 Saturday Severe Weather Outlook It’s very possible I will be heading out east Saturday on a storm chase! If the computer models hold, the target area will be in the Missouri boot heel southward into eastern Arkansas. Portions of Texas might be at risk as well.
The overall situation is a large upper level trough with two shorter waves (areas of stronger winds/every) rotating through this system. The first of these waves will possible produce severe weather in the Ozarks Friday.
The second wave will come out into the threat area on Saturday. It appears is if this feature can induce a weak low pressure system to form immediately to the west of the outlook area. If this indeed happens, then the threat for significant severe weather will go up!
The 12 run of the NAM is interesting in that it shows an area of rather high EHI’s from northeast Texas to southern Tennesee.
I will update this chase forecast through the week as things can and do change from day to day. Friday’s severe weather threat is covered in another blog!
Meteorologist Ted Keller posted this in Forecast Discussion, Storm Chase Discussion on March 7th, 2010
“Upstream” will have a special show tonight at 8 pm. This is a live web show with a chat, join in, and we’ll talk about the upcoming week.
An interesting set of storm chase possibilities exists over the next few days as a general trough of low pressure develops out west with several wind maximums rotating through it. All model references are to today’s 12 run.
The first is Monday as the first punch of stronger jet stream winds work their way out into the Great Plains. While the best bulk shear will be west of the maximum instability axis, there does appear to be support for some storms along the dry line from western Oklahoma curving northwest into SW Kansas. This was the chase of choice for me for many days, especially when the models were showing it more to the east, but the distance as well as the strength/alignment of the various parameters makes me want to abandon this chase for now.
This same shortwave lifts northeast on Tuesday. A weak surface low follows this feature into eastern Kansas and on this point, both models agree. There is a cold core signal on this day northeast of the surface low which would include Kansas eastward into central Missouri which would include the northern and western portion of the KOLR/KFSX viewing area. Of course, the best instability axis would be in the ArkLaTex area southward into eastern Texas.
A second area of maximum winds comes around on Wednesday. There are differences between the NAM and the GFS with regard to the placement of the surface low by 6 pm Wednesday with the NAM more to the west in eastern Oklahoma. This can be traced to differences in the placement of the upper level jet max. This day will need to watched in the Ozarks and points eastward. The GFS develops an instability axis over southern Illinois while the NAM keeps it over the Ozarks.
 NAM Surface/Lifted Index 6 pm Wednesday.  GFS Surface/Lifted Index 6 pm Wednesday. Ultimately, one cannot ignore the climatological significance of the alignment and strength of the upper level jet Thursday and Friday over the southern and eastern U.S. with progged 90 knot winds at 500 mb and 160 knots at 250 mb Thursday at 6 pm over the Texas and Louisiana. The air would be unstable enough as forecast ahead of the surface front and curling northeast of the surface low into the Tennessee and Ohio river valleys to produce severe weather.
 GFS 500 Winds 6 pm Thursday  GFS Lifted Index 6 pm Thursday
Meteorologist Ted Keller posted this in Storm Chase Discussion on March 4th, 2010
 GFS CAPE at 6 pm Monday. The evolving storm system for next week might provide some marginal chasing opportunities but the limiting factors for me would be distance and potential.
Sunday might produce some results but this would occur over far west Texas in a marginal set-up so unless something changes, Sunday is unlikely chase day.
Monday on the other hand is still a bit questionable but it does offer the intriguing possibility of weak tornadoes which occur with cold core upper level low pressure areas.
Meteorologist Jon Davies report on such events
These set-ups depend greatly on surface heating, cold air aloft, backing winds and a boundary of some kind, usually a warm/stationary or occluded front. CAPE, a measure of instability, will often some up as marginal but as Jon points out, if the CAPE is mostly in the lowest layers of the atmosphere than a more volatile situation can occur. He also emphasizes “pattern matching” over the actual values of the various parameters.
The GFS model has waivered a bit on the position of the axis of unstable air with this mornings’ run placing it more south than previous runs in southern Oklahoma. I have seen it into Kansas just a day ago.
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