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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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 an ENHANCED risk of severe thunderstorms: ACROSS PARTS OF THE CENTRAL PLAINS…
The Storm Prediction Center (SPC), has issued a SLIGHT risk of severe thunderstorms: ACROSS PARTS OF THE SOUTHERN MID-ATLANTIC…
…SPC SUMMARY…
Scattered severe thunderstorms are likely across parts of the Great Plains, beginning mainly this evening and continuing overnight. Several tornadoes, large to very large hail, and damaging wind gusts all appear possible. Strong tornadoes may occur this evening across parts of Kansas and Nebraska.
SPC DAY 1 SEVERE THUNDERSTORM OUTLOOK MAPS (first image linked to current SPC outlook)
TORNADO PROBABILITY
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.
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.
Based on my analysis of the current outlook, CIPS, NAM 3km, and SPC SREF forecast models, information derived from forecast indices indicate all severe threats are probable. Based on the complexity of the forecast, I highly recommend reading the outlook text. The highest threat at time of analysis appears to be tornado activity and significant hail. Tornadoes will be a threat mainly within the ENHANCED and a portion of the surrounding SLIGHT risk area. Not that I don’t know how to forecast, or am copying the SPC forecast, I thought it important to post a portion of the very long outlook text, as the timing and forecast pattern are going to complex. From the SPC outlook:
Northern/Central Plains (Kansas/Nebraska/South Dakota)…
A cap and the late timing of large-scale ascent associated with the ejecting upper cyclone will likely inhibit convective development across the northern/central Plains through at least late afternoon. Still, low-level moisture will gradually increase through the day, with surface dewpoints of at least upper 50s to low 60s becoming common by early this evening across the warm sector. Steep mid-level lapse rates and cooling thermal profiles aloft are expected to contribute to substantial MLCAPE by the peak of the diurnal heating cycle, with values likely ranging around 2000-3000 J/kg. With gradually strengthening mid/upper-level flow anticipated, deep-layer shear should also become sufficiently strong to support a mix of supercells and multicells across this region. Convective initiation should be delayed across much of KS/NE/SD until around 00Z as a southerly low-level jet rapidly strengthens to 50-60 kt. Very large hail (around 2-3 inches in diameter) will be a threat with any supercells that can form along/near the warm front, or southward along the length of the dryline into western KS. Low-level hodographs are forecast to become enlarged/curved in the 00-06Z time frame tonight, and the threat for tornadoes is likewise expected to increase with any supercells that can persist and remain at least semi-discrete. Confidence has increased in a more concentrated corridor of tornado potential across parts of western/central KS into central NE, where supercells appear most likely in very favorable thermodynamic and kinematic parameter space. Given the forecast strength of the low-level shear, strong tornadoes appear possible this evening/tonight across this area. Severe/damaging winds will also be possible as convection attempts to grow upscale into one or more clusters overnight. Even with nocturnal cooling, these severe/damaging winds may persist given the ample reservoir of buoyancy available.
The peak of the intensity, time of initiation, and peak of the forecast indices, mainly over the ENHANCED risk area should be between 00 – 06Z (7:00 p.m. – 1:00 a.m. CDT). Based on analyzed forecast CAPE values, lifted index values, and steep mid level lapse, combined with what appears to be just enough deep layer shear, should produce significant hail over the SPC hatched areas. Based on forecast 0-3km SRH, EHI values combined with shear and premise of a strengthening LLJ, tornadoes within the ENHANCED risk outline, especially the hatched area, may become strong (EF2+). The following were the forecast parameters and indices analyzed this morning. Bear in mind, indices recorded below are at the time of peak intensity. Indices meanings can be accessed further on in the synopsis:
SBCAPE: 2500 – 3000 j/kg-1
MLCAPE: 2000 –3000 j/kg-1
MUCAPE: 2000 – 2500 j/kg-1
SRH 0 -1 km: 250 – 300 m2/s2
SRH 0 -3 km: 300 – 400 m2/s2
SRH EFFECTIVE: 200 – 300 m2/s2
L. I.: -3 to -8
STP: 2 – 6
SCP: 6 – 17
0 -6 km SHEAR: 50 – 60 kts
EFF. SHEAR: 35 – 40 kts
MID LEVEL LAPSE RATE: 8.0 – 9.0C
DEWPOINT: 59F – 65F
EHI: 4.0 – 6.0
TOTAL TOTALS INDEX: 52 – 54C
K INDEX: 33 – 35C
SWEAT INDEX: 550 – 650
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 model. 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 (1:00 p.m. 15APR. – 9:00 p.m. CDT 15 APR.)
NAM 3KM STP FORECAST (1:00 p.m. 15APR. – 9:00 p.m. CDT 15 APR.)
HRRR SCP FORECAST (1:00 p.m. 15APR. – 9:00 p.m. CDT 15 APR.)
HRRR SCP FORECAST (1:00 p.m. 15APR. – 9:00 p.m. CDT 15 APR.)
SPC SREF SIGNIFICANT TORNADO PARAMETER >1 FORECAST 21Z
00Z
03Z
This is from the 12Z update from NADOCAST.
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
I will not be updating tomorrow, as my wife has a doctor appointment in the morning. There is however another ENHANCED risk outline for tomorrow. Please refer to the SPC homepage link for updated information:
DAY 2 CONVECTIVE OUTLOOK
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 