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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: ACROSS CENTRAL AND EASTERN OKLAHOMA INTO SOUTHEASTERN KANSAS…
A few supercells are possible late Wednesday afternoon and evening from southeastern Kansas to central/eastern Oklahoma. A few strong storms may also impact areas west of the Oregon Cascades, accompanied by at least some risk for severe weather.
A progressive zonal flow pattern is expected across much of the central/eastern CONUS ahead of an increasingly southwesterly component associated with a large digging Pacific trough along the West Coast. Within the low-amplitude flow, several shortwave troughs and a cold front moving across the Plains/Midwest will serve as the focus for isolated severe storms Wednesday morning and afternoon from the southern Plains to the lower Ohio Valley.
CURRENT SPC DAY 2 OUTLOOK LINK
SPC DAY 2 CONVECTIVE OUTLOOK
DAMAGING THUNDERSTORM WIND PROBABILITY
Based on analysis of the SPC outlook, the main threat for tomorrow at the moment appears to be damaging winds and possibly some large hail to marginally severe hail, especially over the risk area. SPC suggests elevated storms for the Ozarks and lower Ohio Valley. SBCAPE values of 500 – 2500 j/kg, and MLCAPE of 500 – 1500 j/kg, along with effective bulk shear of 30 – 40 kts support the hail forecast. Tornadoes will be possible with the more intense/dominate cells, given analyzed long hodographs, combined with the mentioned shear.
STP, SCP, VGP and EHI values were analyzed to be low to moderate.
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
Both F5 DATA, NAM 3km, and SPC SREF models show strongest activity close to 1:00 p. m. CDT. and diminishing after 7:00 p. m. CDT, near the 10:00 p. m. CDT time frame.
Based on this, and my analysis of various tornado indices using the F5 DATA NAM-WRF model, and the NAM 3km mesoscale model, the following outlines in the F5 DATA maps indicate where the best probability for tornadic activity to occur. This is based on where analyzed indices overlap on the maps.
F5 DATA NAM – WRF 1:00 P. M. CDT
4:00 P. M. CDT
7:00 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 (1:00 P. M. CDT APR 20 – 10:00 P. M. CDT APR 20)
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: firstname.lastname@example.org
Have a blessed evening!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
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