SIGNIFICANT SEVERE WEATHER EVENT / MODERATE RISK FOR SEVERE THUNDERSTORMS FORECAST…WIDEST DISSEMINATION REQUESTED…ISSUED APR. 12, 2022…8:25 P. M. EDT7 min read
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(T. F. “Storm” Walsh)
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Please be aware, even though I do not post every night, rest assured I am continuously monitoring various areas for any significant weather. I will be taking Sundays off (family time), unless we have active systems that may be posing a threat (i.e. Tropical, Winter Weather, Coastal Storms, etc.).
I will reiterate, my forecasts are based on the available information at the time of analysis, and are only as accurate as the information analyzed and the solutions provided.
Good evening everyone!
Since I get home from work later each evening, and do not get to perform analysis until 6:00 p. m. or after, I have decided to do the severe weather reports a different way. I have decide to post the SPC outlook link, so all may view the full report from the SPC. My portion of the forecast will try to briefly point out key features in my interpretation, and analyzing indices to draw the outlined F5 DATA maps, in an effort to try to finish up at a more decent hour.
The Storm Prediction Center (SPC), has issued an MODERATE RISK OF SEVERE THUNDERSTORMS in the current DAY 2 outlook: ACROSS THE LOWER TO MID MS RIVER VALLEY…
Numerous severe thunderstorms appear likely across a large portion of the lower/mid Mississippi Valley into the Midwest, and lower Ohio Valley on Wednesday. Damaging winds, some of which could be significant, several tornadoes (some strong), and large to very large hail will likely occur.
SPC DAY 2 CONVECTIVE OUTLOOK LINK:
SPC DAY 2 CONVECTIVE OUTLOOK
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 – EF5 tornadoes within 25 miles of a point.
Probability of one inch diameter hail or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of two inch diameter hail or larger within 25 miles of a point.
DAMAGING THUNDERSTORM WIND PROBABILITY
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% or greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Based on the SPC outlook and analyzing severe and tornado indices, this event has the markings of a regional severe weather outbreak. ALL SPC maps indicate all threats could be significant. This means the probability of some strong, long track tornadoes (EF2+), large significant hail, and strong, damaging thunderstorm gusts and straight line winds, over the MODERATE and ENHANCED risk areas. The best probability for the strongest severe threats appears to be over the lower MS river valley, however strong severe threats will also extend into the mid MS/ lower OH river valleys. With deep moisture, adequate deep layer shear, forecast ESRH of 300-400 m2/s2, moderate to strong CAPE values, and steep lapse rates, along with the indices I analyzed this evening from the NAM – WRF model (though the NAM 3km has a little lower STP indices, It would not surprise me to see SPC upgrade a portion of the MODERATE risk area to aHIGH risk. This will however, depend on whether or not the forecast indices pan out.
Based on my analysis this evening, this could become a PDS (Particularly Dangerous Situation) for areas under the moderate risk area, within the strongest indices areas. Residents under the enhanced and moderate risk areas should monitor NOAA Weather Radio, Local NWS statements, and local news channels throughout the afternoon and evening tomorrow.
The following indices were analyzed this evening, regarding the mentioned models:
SBCAPE: 1000 – 3000 j/kg
MLCAPE: 1000 – 2500 j/kg
SRH: 300 – 400 m2/s2
L. I.: -4 to -8
SWEAT: 400 – 525
EHI: 2 – 6
VGP: 0.3 – 1.0
STP: 3 – 11 (early afternoon), 4 – 16 (late afternoon)
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
The following outlined areas indicate where the modeling suggests the best / highest probabilities for the strongest severe weather and tornadoes could occur. The strongest of the indices will be located over the area and south, of where the SPC has the 15% probability for significant tornadoes. Although the modeling suggests this could begin by 10:00 a. m. CDT, I do not believe there will be enough daytime heating to support significant tornado activity until around 1:00 p. m. CDT.
F5 DATA NAM – WRF 10:00 A. M. CDT
1:00 P. M. CDT
4:00 P. M. CDT
7:00 P. M. CDT
Unfortunately, the NAM – WRF pulled a glitch, and did not have an updated map for 10:00 p. m. CDT. However, I will take the NAM 3km animation maps out to 10:00 p. m. CDT to give you and idea where the strongest STP and SCP will be approximated.
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 (10:00 A. M. CDT APR 13 – 10:00 P. M. CDT APR 13)
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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