May 27, 2024

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ENHANCED SEVERE WEATHER RISK FORECAST SYNOPSIS…ISSUED MAY 01, 2024…12:00 NOON EDT

7 min read

Disclaimer:  This is not affiliated with the National Hurricane Center, Hurricane Hunters, Storm Prediction Center, or National Weather Service.  ALL forecasts herein are the result of my analysis, (to which you will see me at times, insert excerpts from various agencies due to the nature of the importance of the information) and I am solely responsible for the content.  As ALWAYS, follow the National Hurricane Center, National Weather Service, and your local Emergency Management officials for emergency decisions.  In addition, this is strictly a FORECAST OFFICE.  I CANNOT make decisions regarding travel plans, etc.  My purpose, is to provide you the information, based solely on information I analyze, and the accuracy of the information at hand of the time of analysis, so you may make informed decisions.
(T. F. “Storm” Walsh)

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Good day everyone!

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.

The outlined maps you were used to seeing from my F5 DATA software, are no longer around and operational.  This means I have lost quite a bit of data to analyze but I will try to make the severe weather forecasts as accurate and understandable as possible.
https://www.spc.noaa.gov/new/images/SPC_outlook_final_updated.png
CATEGORICAL OUTLOOK CONVERSION TABLE FOR DAY 1 OUTLOOKS
image002day1.conv

The Storm Prediction Center (SPC), has issued an ENHANCED risk of severe thunderstorms: IN WESTERN OKLAHOMA…THE EASTERN TEXAS PANHANDLE AND NORTHWEST/WEST-CENTRAL TEXAS…

…SPC SUMMARY…
The greatest threat today for large to very large hail, severe thunderstorm gusts and a few tornadoes will be in western Oklahoma, the eastern Texas Panhandle and northwest/west-central Texas.

SPC DAY 1 SEVERE THUNDERSTORM OUTLOOK MAPS (first image linked to current SPC outlook.  Click for any updated outlook maps)
day1otlk_1300
TORNADO PROBABILITY
day1probotlk_1300_torn
Probability of a tornado within 25 miles of a point.

HAIL PROBABILITY
day1probotlk_1300_hail
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 WINDS PROBABILITY

day1probotlk_1300_wind
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.

Based on my analysis of the current outlook, CIPS, NAM 3km, HRRR and SPC SREF forecast models, information derived from forecast indices indicate all severe threats are probable, with the highest potential being large hail, and damaging thunderstorm gusts.  Based on the conversion table above, a slight chance for tornadoes is probable.  Based on analysis of severe  weather indices animations from recent modeling, the stronger thunderstorm and severe weather activity appears once again to occur from 21Z – 00Z (4:00 p.m. – 7:00 p.m. CDT) over the ENHANCED risk outline, and south over the SLIGHT risk outline from Oklahoma into Texas through the late evening hours.

Based on moderate deep layer shear, moderate to very unstable lifted indices, moderate to steep mid level lapse rates, and CAPE values, large to significant hail may be experienced within the SPC hail outlook hatched area. Though the SPC does not indicate any significant tornado activity (most likely due the only somewhat favorable hodographs mentioned in the report, moderate deep layer shear, weaker effective shear, and lower effective SRH),  based on 0-3km SRH values, and MLCAPE values producing the forecast EHI, I would not rule out the probability of an isolated EF2 tornado where the higher STP values may occur.    This would apply mainly to the ENHANCED outline within the 5% tornado probability area.

The following were the forecast parameters and indices analyzed this morning, with the max. values pertaining to the ENHANCED risk and 5% tornado outline area.  Bear in mind, indices recorded below are for the time of peak intensity which could be between 21Z – 00Z CDT (4:00 P.M. – 7:00 P.M.).  Indices meanings can be accessed further on in the synopsis:
SBCAPE: 2000 – 3500 j/kg-1
MLCAPE: 2500 –3500 j/kg-1
MUCAPE: 2500 – 3500 j/kg-1
SRH 0 -1 km: 100 – 250 m2/s2
SRH 0 -3 km: 200 – 400 m2/s2
SRH EFFECTIVE: 100 – 250 m2/s2

L. I.: -4 to -9
SCP: 7 – 16
STP: 1 – 5
0 -6 km SHEAR: 40 – 50 kts
EFF. SHEAR: 30 – 40kts
MID LEVEL LAPSE RATE: 7.5 – 8.5C
DEWPOINT: 64F – 71F
EHI: 3.1 – 3.9
TOTAL TOTALS INDEX: 56 – 57C
K INDEX: 28 – 40C
SWEAT INDEX:
550 – 575
Screenshot 2024-04-26 at 19-04-32 Env Parameters and Indices
Screenshot 2024-04-27 at 08-58-07 Env Parameters and Indices
Screenshot 2024-04-27 at 08-56-33 Env Parameters and Indices
Screenshot 2024-04-27 at 08-59-15 Env Parameters and Indices

The full operational utility of the EHI is not yet completely known. In addition, there is some discrepancy as to what the minimum threshold is for severe thunderstorms and tornadoes. However, general threshold values are given below.
Screenshot 2024-05-01 at 08-46-17 Env Parameters and Indices
A little fact on SRH values and tornadoes from NOAA / NWS
Storm Relative Helicity (m2 s-2)
SRH (Storm Relative Helicity) is a measure of the potential for cyclonic updraft rotation in right-moving supercells, and is calculated for the lowest 1-km and 3-km layers above ground level. There is no clear threshold value for SRH when forecasting supercells, since the formation of supercells appears to be related more strongly to the deeper layer vertical shear. Larger values of 0-3-km SRH (greater than 250 m2 s-2) and 0-1-km SRH (greater than 100 m2 s-2), however, do suggest an increased threat of tornadoes with supercells. For SRH, larger values are generally better, but there are no clear thresholds between non-tornadic and significant tornadic supercells.
Screenshot 2024-05-01 at 08-51-07 Env Parameters and Indices.SRH

STP
( Significant Tornado Parameter) EXPLAINED:

A majority of significant tornadoes (EF2 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.

SCP (Supercell Composite Parameter) EXPLAINED:
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.

SWEAT INDEX
Screenshot 2024-03-30 at 09-30-56 SWEAT Index

The following are the SCP (Supercell Composite Parameter) and STP (Significant Tornado Parameter) forecast maps from the NAM and HRRR model.  I decided to post both, given the discrepancies noted.  Generally, the higher the values and brighter the color, indicates a greater probability of strong thunderstorm and tornadic activity over an area:
NAM 3KM SCP FORECAST (4:00 p.m. 01 MAY –  9:00 p.m. CDT 01 MAY)
nam-nest-oklahoma-supercell_comp-1714564800-1714597200-1714615200-80
NAM 3KM STP FORECAST (4:00 p.m. 01 MAY –  9:00 p.m. CDT 01 MAY)
nam-nest-oklahoma-sig_tor-1714564800-1714597200-1714615200-80
HRRR SCP FORECAST (4:00 p.m. 01 MAY –  9:00 p.m. CDT 01 MAY)hrrr-oklahoma-supercell_comp-1714568400-1714597200-1714615200-80
HRRR STP FORECAST (4:00 p.m. 01 MAY –  9:00 p.m. CDT 01 MAY)hrrr-oklahoma-sig_tor-1714568400-1714597200-1714615200-80
This is from the 12Z update from NADOCAST and 00Z update from CSU-MLP.  Click on the image from NADOCAST for the updates page.  Once there, click on the time on the left (i.e. 12Z), then scroll to (models-conus-sigtor abs -calib)
nadocast_2022_models_conus_sig_tornado_abs_calib_20240501_t12z_f02-23
severe_ml_day1_all_gefso_050212
Please use the following maps, which should update automatically, for Mesoscale Discussions and Convective Watches.  You may have to refresh your browser, or click on the graphics.  I have provided the SPC homepage link below, so you may get the updated information regarding any changes to the outlook:
SPC MESOSCALE DISCUSSIONS (CLICK IMAGE FOR UPDATES)
Valid MD Image
SPC CONVECTIVE WATCHES (CLICK IMAGE FOR UPDATES)
Valid WW Image
IF A TORNADO WARNING IS ISSUED FOR YOUR AREA, IMMEDIATELY TAKE STURDY AND SAFE SHELTER
The following sites will explain most of the severe weather and tornado values listed above, and will give you an idea of what to expect:
ENVIRONMENTAL INDICES AND PARAMETERS NWS
https://www.weather.gov/lmk/indices

THE WEATHER PREDICTION
http://www.theweatherprediction.com/severe/indices/

SPC HOMEPAGE LINK
https://www.spc.noaa.gov/classic.html

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)

NWS DOPPLER RADAR LOOP (LINKED, CLICK RADAR MAP)
canvas.radr_.us_
RAP RADAR (CLICK IMAGE THEN GO TO LOOP DURATION AND PICK LENGTH OF LOOP, THEN CLICK RADAR SITE)
CARIBBEAN RADAR (CLICK IMAGE TO ACCESS ANIMATION)
radar_comp_Eng
You may direct any questions by contacting me personally, ANYTIME, at: twalsh22000@yahoo.com

Have a blessed day!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST

About palmharborforecastcenter

I am a Tropical Forecast meteorologist, providing hurricane forecasts during the Atlantic Hurricane Season. I retired from the U.S. Coast Guard in July of 2001. Meteorology became my passion in high school, and I have continued my educational background in meteorology since 1996, when I undertook the study of Tropical Meteorology. While working toward my degree, I had to unexpectedly withdraw from college due to my oldest sons medical reasons. I do however, meet the educational criteria of the AMS to be recognized as a meteorologist. Studies include, but are not limited to the Navy Aerographers Mate course, Naval METOC meteorology course, Meteorology 2010 Sophomore level course while attending St. Petersburg College, Clearwater, FL., Basic Forecasting course for operational meteorologists from Rapid WX, meteorology institute, a four month meteorological internship, and extensive research on numerous meteorological topics such as the MJO, NAO, satellite imagery interpretation, etc.

I have been forecasting Tropical Weather (Tropical Storms and Hurricanes) since 1996, with my main client being three different Coast Guard Commands.

palmharborforecastcenter

2024-05-01 15:57:46

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