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(T. F. “Storm” Walsh)
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Good evening everyone!
The Storm Prediction Center (SPC), has issued a SLIGHT RISK OF SEVERE THUNDERSTORMS in the current DAY 2 outlook: FROM THE UPPER MIDWEST SOUTHWARD ACROSS THE LOWER MO VALLEY INTO THE SOUTHERN PLAINS…
Severe thunderstorms are possible Saturday through Saturday night in a corridor from parts of the Upper Midwest into the southern Great Plains. This may include a risk for tornadoes, strong wind gusts and hail.
CURRENT SPC DAY 2 OUTLOOK LINK
SPC DAY 2 CONVECTIVE OUTLOOK
DAMAGING THUNDERSTORM WIND PROBABILITY
Based on my analysis this evening of the SPC DAY 2 Outlook (which if you go to the SPC DAY 2 link), you’ll see it’s very lengthy. To simplify this, the thermodynamics of the atmosphere over the region under the slight risk outline, will support both discrete supercells and bowing line segments in some areas, which will be supportive of the two main severe threats of damaging thunderstorm winds and large hail.
Analysis of severe and tornado indices yielded CAPE values in the moderate range, EHI, VGP, SWEAT and STP values in the low to moderate range. Currently, based on the information, I am not expecting strong/significant tornadoes. Based on the SPC tornado probability map, you’ll note two areas outlined at 5%. Given the thermodynamic setup forecast for tomorrow, tornadoes can occur anywhere within the slight risk area.
A majority of significant tornadoes (F2 or greater damage) have been associated with STP values greater than 1, while most non-tornadic supercells have been associated with values less than 1 in a large sample of RAP analysis proximity soundings.
A multiple ingredient, composite index that includes effective storm-relative helicity (ESRH, based on Bunkers right supercell motion), most unstable parcel CAPE (muCAPE) and convective inhibition (muCIN), and effective bulk wind difference (EBWD). Each ingredient is normalized to supercell “threshold” values, and larger values of SCP denote greater “overlap” in the three supercell ingredients. Only positive values of SCP are displayed, which correspond to environments favoring right-moving (cyclonic) supercells.
VGP: The VGP (Vorticity Generation Parameter) is meant to estimate the rate of tilting and stretching of horizontal vorticity by a thunderstorm updraft. Values greater than 0.2 m s-2 suggest an increasing possibility of tornadic storms.
The following sites will explain most of these values, and will give you an idea of what to expect:
ENVIRONMENTAL INDICES AND PARAMETERS NWS
THE WEATHER PREDICTION
Based on analysis of F5 DATA NAM-WRF, NAM 3km, and SPC SREF models the strongest indices appear AOA 7:00 p. m. CDT through 10:00 p. m. CDT. The severe threat begins to diminish thereafter.
Based on this, the following outlines in the F5 DATA maps indicate where the best probability for tornadic activity should occur. This is based on where analyzed indices overlap on the maps.
F5 DATA NAM – WRF 4:00 P. M. CDT
7:00 P. M. CDT
10:00 P. M. CDT
The following NAM 3km animations indicate the locations and strength of the forecast STP (Significant Tornado Parameter) index, and SCP (Supercell Composite Parameter) index.
NAM 3km STP ANIMATION (4:00 P. M. CDT APR 23 – 1:00 A. M. CDT APR 24)
NAM 3km SCP ANIMATION
Please use the following maps for all days, which should update automatically, for Mesoscale Discussions and Convective Watches. You may have to refresh your browser, or click on the graphics. I am also providing the SPC homepage link, so you may get the updated information regarding any changes to the outlook:
SPC MESOSCALE DISCUSSIONS (CLICK IMAGE FOR UPDATES)
SPC CONVECTIVE WATCHES (CLICK IMAGE FOR UPDATES)
SPC HOMEPAGE LINK
IF A TORNADO WARNING IS ISSUED FOR YOUR AREA, IMMEDIATELY TAKE STURDY AND SAFE SHELTER
The following NWS Watch / Warning map will provide local NWS information for your area. Click the image, then once it refreshes, click on your area of interest to view any special weather statements, hazards or advisories for your area.
NWS WATCH / WARNING DISPLAY (LINKED…CLICK MAP, THEN YOUR AREA)
WSI DOPPLER RADAR LOOP (LINKED)
RAP RADAR (CLICK IMAGE THEN RADAR SITE)
You may direct any questions by contacting me personally, ANYTIME, at: email@example.com
Have a blessed evening!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
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