Disclaimer: This site 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 be out of the office from May 20 through June 01 as we will be traveling to Wyoming for our grandsons high school graduation. For updates on severe weather and / or tropics, please come to this site, and use the following links for updates. I will resume tropical outlooks on June 03.
https://www.spc.noaa.gov/classic.html
https://www.nhc.noaa.gov/
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.
CATEGORICAL OUTLOOK CONVERSION TABLE FOR DAY 1 OUTLOOKS
The Storm Prediction Center (SPC), has issued a SLIGHT risk of severe thunderstorms: OVER PARTS OF NORTHWEST…NORTH-CENTRAL AND CENTRAL TEXAS…
…SPC SUMMARY…
Strong to severe thunderstorms will be possible today from parts of the Upper Midwest to the southern Plains. The greatest potential appears to be over parts of northwest, north-central and central Texas, where large to very large hail, severe gusts and a couple tornadoes are possible.
SPC DAY 1 SEVERE THUNDERSTORM OUTLOOK MAPS (first image linked to current SPC outlook. Click for any updated outlook maps)
TORNADO PROBABILITY
Probability of a tornado within 25 miles of a point.
HAIL PROBABILITY
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
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
The 13Z outlook update from the SPC is rather lengthy and complex, and I recommend viewing. The SPC link is provided further on in this synopsis, or you can access the outlook by clicking on the SPC day 1 outlook map above.
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 isolated 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 at approximately 20Z – 21Z (3:00 p.m. – 4:00 p.m. CDT) over the SLIGHT risk outline.
Based on moderate deep layer shear, very unstable lifted indices, moderate to steep mid level lapse rates, and forecast CAPE values, large to significant hail may be experienced within the SPC hail outlook hatched area. Analysis of forecast indices within and just around the SLIGHT risk area tends to indicate any tornado activity should be on the weak side, based on minimal SRH values and EHI values from o6Z model runs. It was noted in analysis this morning, that SRH (0-3km) values over Louisiana and Arkansas were in the 400 – 700 range, which would tend to indicate strong to violent tornadoes. However the lack of significant instability (Minimal L.I., lower end CAPE, lower shear), does not support such a scenario.
The following were the forecast parameters and indices analyzed this morning, with the max. values pertaining to the SLIGHT 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 – 3000 j/kg-1
MLCAPE: 2000 –2500 j/kg-1
MUCAPE: 2000 – 3500 j/kg-1
SRH 0 -1 km: 50 – 100 m2/s2
SRH 0 -3 km: 150 – 250 m2/s2
SRH EFFECTIVE: 50 – 100 m2/s2
L. I.: -6 to -10
SCP: 3 – 12
STP: 1 – 3
0 -6 km SHEAR: 40 – 50 kts
EFF. SHEAR: 35 – 40kts
MID LEVEL LAPSE RATE: 7.5 – 8.0C
DEWPOINT: 63F – 70F
EHI: 2.0 – 3.0
TOTAL TOTALS INDEX: 51 – 56C
K INDEX: 28 – 36C
SWEAT INDEX: 350 – 500
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.
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.
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
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. 02 MAY – 10:00 p.m. CDT 02 MAY)
NAM 3KM STP FORECAST (4:00 p.m. 02 MAY – 10:00 p.m. CDT 02 MAY)
HRRR SCP FORECAST (4:00 p.m. 02 MAY – 10:00 p.m. CDT 02 MAY)
HRRR STP FORECAST (4:00 p.m. 01 MAY – 10:00 p.m. CDT 02 MAY)
This is from the 00Z 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)
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)
SPC CONVECTIVE WATCHES (CLICK IMAGE FOR UPDATES)
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)
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)
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
WEST CENTRAL FLORIDA HURRICANE and SEVERE WEATHER FORECAST CENTER 