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(T. F. “Storm” Walsh)

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Good day everyone!

The Storm Prediction Center (SPC) has issued a MARGINAL risk for severe thunderstorms in the current DAY 1 Outlook: FROM SOUTHWEST TEXAS INTO CENTRAL OKLAHOMA…

…SPC SUMMARY…
Marginally severe storms are possible from late tonight into the early morning on Thursday from parts of west and northwest Texas northeastward into Oklahoma.
SPC DAY 1 SEVERE THUNDERSTORM OUTLOOK (LINKED FOR OUTLOOK TEXT)

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.
DAMAGING THUNDERSTORM WIND PROBABILITY

Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
CSU – MLP DAY 1 FORECAST (CLICK FOR LARGER IMAGE)

NSSL ML PROBABILITY DAY 1

The SPC indicates a MARGINAL risk for severe weather in the DAY 2 outlook, and a SLIGHT risk in the DAY 3 outlook:
SPC DAY 2 AND DAY 3 OUTLOOK (LINKED TO OUTLOOK TEXT)


CSU – MLP DAY 2 AND 3 VS SPC PROBABILITY FORECAST (CLICK FOR LARGER IMAGE)


NSSL ML DAY 2 AND 3

DAY1 PROBABILITY CONVERSION TABLE

SPC DISCUSSION EXCERPT: 
...Southwest TX into Central OK…
Water-vapor imagery this morning shows a mid-level shortwave trough immediately west of Baja California while a progressive flow regime prevails across the northern half of the Lower 48. The aforementioned upper disturbance is forecast to quickly move east across the Sonoran and Chihuahuan deserts and into west/northwest TX by early Thursday morning.

A reservoir of partially modified Gulf moisture (60s deg F surface dewpoints) resides over the coastal plain of TX this morning. As the upper trough approaches the southern Great Plains tonight, strengthening low-level flow will advect this moisture northwestward into parts of northwest TX into central OK during the 08-12 UTC period. Although the primary cyclone will remain near the CO-NM-OK-KS-TX border region while deepening considerably, the attendant warm front will serve as the main low-level feature of interest. Warm advection/isentropic lift will favor isolated to scattered showers and thunderstorms developing late tonight over west into northwest TX and eventually into central OK. Model-based soundings imply elevated parcels and MUCAPE ranging from 500-1000 J/kg amidst strong deep-layer shear. An isolated risk for large hail may accompany the stronger storms along with the possibility of localized severe gusts.

The following maps are from NADOCAST for tornado and hail probabilities.  The TORNADO and HAIL probability was shown to be <1%. 
12Z NADOCAST TORNADO PROBABILITY (CLICK FOR LARGER IMAGE)

12Z NADOCAST SIGTOR PROBABILITY (CLICK FOR LARGER IMAGE)

12Z NADOCAST HAIL PROBABILITY (CLICK FOR LARGER IMAGE)

12Z NADOCAST SIGHAIL PROBABILITY (CLICK FOR LARGER IMAGE)

Based on my analysis of the severe weather indices, the forecast calls for a marginally unstable atmosphere over the risk area.  The main threat at this time appears to be damaging thunderstorm winds and gusts, based on bulk shear values, and DCAPE of 600+ j/kg-1.  Given the strong bulk shear and the maximum MUCAPE value, there will be an isolated risk for large hail associated with the strongest storms. Based on analysis of the overall forecast indices, a borderline probability exists for an isolated, brief and weak tornado within the area of the strongest indices, based on bulk shear, SRH, and veering winds with height. The strongest forecast indices and parameters should occur within the 5% WIND and 5% HAIL outline, south of the TX/OK border, and should be where the strongest storms occur during the overnight and early morning hours.  By later tomorrow morning, these indices will be moving northward into OK., and will be reflected in the outlook for tomorrow.  Storms will be ongoing by 12Z – 14Z CST over OK, and the outlook will explain the progression.

Based on analysis of model animations, the current outlook, and analysis of indices, the strongest convection and indices should occur approximately between 3:00 A.M. CST JAN 08 – 8:00 A.M. CST JAN. 08.  Please visit the SPC homepage via the link provided for any changes to the forecast today.
CAPE VALUES FORECAST


DEW POINT FORECAST

Indices were analyzed from the NAM 3KM, HRRR 3KM, CIPS DETERMINISTIC, and SPC SREF model guidance.

The following were the forecast parameters and indices analyzed this morning.  Bear in mind, MAXIMUM indices recorded below are for the time of peak intensity.  Some indices meanings are posted below the indices themselves, and the NWS page containing a more extensive explanation can be accessed further on in the synopsis:
SBCAPE: 50 – 750 j/kg-1                  
MLCAPE: 250 – 500 j/kg-1                   
MUCAPE: 500 – 1000 j/kg-1                
SRH 0 -1 km: 200 – 250 m2/s2               
SRH 0 -3 km: 200 – 300 m2/s2        
SRH EFFECTIVE: 100 – 200 m2/s2          
L. I.: 0 to -2                                                    
SCP: 1.0 – 2.0                                          
STP: 0.4 – 1.2  
0 -6 km SHEAR: 50 kts – 60 kts                  
EFF. SHEAR: 30 kts – 40kts                        
MID LEVEL LAPSE RATE: 6.5C – 7.5C   
DEWPOINT: 56F – 62F                                    
EHI: 0.4 – 0.8                                      
TOTAL TOTALS INDEX: 51C                     
K INDEX: 26C to 33C                                          
SWEAT INDEX: 450 – 500                             
THOMPSON INDEX: 26 to 35         
CRAVEN – BROOKS INDEX: 5,000 – 10,000    

CAPE

ENERGY HELICITY INDEX

K INDEX

TOTAL TOTALS INDEX

STORM RELATIVE HELICITY

LIFTED INDEX

SWEAT VALUES

THOMPSON INDEX

Craven SigSvr Parameter:
The simple product of 100mb MLCAPE and 0-6km magnitude of the vector difference (m/s; often referred to as “deep layer shear”) accounts for the compensation between instability and shear magnitude. Using a database of about 60,000 soundings, the majority of significant severe events (2+ inch hail, 65+ knot winds, F2+ tornadoes) occur when the product exceeds 20,000 m3/s3.
A little fact on SRH values and tornadoes from NOAA / NWS

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.

The following are the SCP (Supercell Composite Parameter) and STP (Significant Tornado Parameter) forecast maps from the NAM 3KM model.  Generally, the higher the values and brighter the color, indicates a greater probability of strong thunderstorm and / or tornadic activity over an area:
NAM 3KM SCP FORECAST 10:00 P.M. CST JAN. 07 – 8:00 A.M. CST JAN. 08

NAM 3KM STP FORECAST 10:00 P.M. CST JAN. 07 – 8:00 A.M. CST JAN. 08

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:
https://www.spc.noaa.gov/classic.html
SPC MESOSCALE DISCUSSIONS (CLICK IMAGE FOR UPDATES)

SPC CONVECTIVE WATCHES (CLICK IMAGE FOR UPDATES)

IF A TORNADO WARNING IS ISSUED FOR YOUR AREA, TAKE IMMEDIATE SAFE AND STURDY 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/

The following links will connect you to the Excessive Rainfall probabilities and River Flood Outlook:
EXCESSIVE RAINFALL
https://www.wpc.ncep.noaa.gov/qpf/excessive_rainfall_outlook_ero.php

SIGNIFICANT RIVER FLOOD OUTLOOK
https://www.wpc.ncep.noaa.gov/nationalfloodoutlook/index.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 forecasts, 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)
WUNDERGROUND RADAR SUMMARY MAP (CLICK FOR UPDATES)

PRECIPITATION TYPE (CLICK TO ACCESS ANIMATION FEATURE)

CARIBBEAN RADAR (CLICK IMAGE TO ACCESS ANIMATION)

You may direct any questions by contacting me personally, ANYTIME, at: [email protected]

Have a blessed day!

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