andyhb Posted December 25, 2012 Share Posted December 25, 2012 I think I'm gonna go ahead and say that this event may have the highest ceiling of a winter event (before March 1st) since Super Tuesday 2008, all of the parameters tomorrow especially across the southern Gulf Coast states (and possibly extending further north eventually) are pretty scarily high, not only for a Winter event, but for many Spring events as well (with a pretty textbook upper level trough, no less). I seriously hope that people down there are aware of what might be about to happen over the next 48 hours...And I agree that the second high risk for December on record may be indeed in the works, perhaps not with the first outlook, but once the mesoscale becomes clear, because a lot synoptically argues for it...across pretty much all of the models. Link to comment Share on other sites More sharing options...
Disc Posted December 25, 2012 Share Posted December 25, 2012 Given the trends, I am starting to think that a Day-1 High Risk for overall TOR and Severe Wind probabilities may be in order. Just curious, but if that were to happen, have there been any high risks issued in December in the past? Link to comment Share on other sites More sharing options...
thewxmann Posted December 25, 2012 Share Posted December 25, 2012 The strength of the dry punch between 00-06Z Wednesday on the 00Z NAM is just incredible...indicating the intensity of the mid-level system. This allows the QLCS to remain mostly or entirely discrete supercells from extreme E LA / SW MS all the way to GA. In particular, it shows three rounds of tornado-producing supercells: a first round of storms starting 12Z Tuesday with elevated storms becoming surface-based in E/C LA; a second, protracted (meaning nocturnal) outbreak beginning at 21Z Tuesday in S/C MS; and a third, afternoon event at 21Z Wednesday in C AL extending into W GA. The orientation of the surface-700-mb bulk shear relative to the front, in particular, really helps to maintain discrete supercells for a long period of time. This almost reminds me of 04/27/2011, as frightening as it may be to invoke. http://www.emc.ncep....yle/spcprod/00/ Given the trends, I am starting to think that a Day-1 High Risk for overall TOR and Severe Wind probabilities may be in order. I wouldn't go so far as to make comparisons to -the day that cannot be speaketh- but I agree with you on the dry punch. This is an incredibly dynamic system and having the 100kt barb at H5 impinging on a moist and unstable warm sector after dark speaks of a very volatile situation. Link to comment Share on other sites More sharing options...
thewxmann Posted December 25, 2012 Share Posted December 25, 2012 Just curious, but if that were to happen, have there been any high risks issued in December in the past? 12/23/02 http://www.spc.noaa.gov/exper/archive/events/021223/spcotlk-nav-4.html Link to comment Share on other sites More sharing options...
CUmet Posted December 25, 2012 Share Posted December 25, 2012 For what it's worth, I now think tomorrow deserves a high risk. Seeing the 4km NAM, SPC and NSSL WRF models show 1) the WAA rain shield pushing at a good pace towards the NE, leaving at least a several hour window for rapid destabilization to occur ahead of the cold front, and 2) a line of discrete cells as opposed to a solid squall line give me confidence that a major tornado outbreak will indeed occur tomorrow night. At this point, the area I would include in a high risk area includes NE LA, south-central MS and south-central AL. This includes: Baton Rouge, LA Natchez, MS Jackson, MS Hattiesburg, MS Meridian, MS Tuscaloosa, AL Birmingham, AL Montgomery, AL Hope everyone stays safe tomorrow night, as I'm not encouraged by what I see right now. Link to comment Share on other sites More sharing options...
CUmet Posted December 25, 2012 Share Posted December 25, 2012 The strength of the dry punch between 00-06Z Wednesday on the 00Z NAM is just incredible...indicating the intensity of the mid-level system. This allows the QLCS to remain mostly or entirely discrete supercells from extreme E LA / SW MS all the way to GA. In particular, it shows three rounds of tornado-producing supercells: a first round of storms starting 12Z Tuesday with elevated storms becoming surface-based in E/C LA; a second, prolonged (meaning nocturnal) outbreak beginning at 21Z Tuesday in S/C MS; and a third, afternoon event at 21Z Wednesday in C AL extending into W GA. The orientation of the surface-700-mb bulk shear relative to the front, in particular, really helps to maintain discrete supercells for a long period of time. This almost reminds me of 04/27/2011, as frightening as it may be to invoke. http://www.emc.ncep....yle/spcprod/00/ Given the trends, I am starting to think that a Day-1 High Risk for overall TOR and Severe Wind probabilities may be in order. This does actually remind me of a watered-down instability and slightly further south version of the 4/27/11 event. The shape and evolution of the trough and intensity of the wind fields are all quite similar. Even the rain shield associated with the warm front, and the rapid destabilization in its wake is similar, although in this case it'll happen after dark. Link to comment Share on other sites More sharing options...
heavy_wx Posted December 25, 2012 Share Posted December 25, 2012 12/23/02 http://www.spc.noaa....otlk-nav-4.html Interesting, that date has been showing up near the top of the CIPS analogs for the past several days. Link to comment Share on other sites More sharing options...
DaculaWeather Posted December 25, 2012 Share Posted December 25, 2012 Critical Weather Day Has Been Declared START: 1200Z TUE DEC 25 2012 END: 1200Z FRI DEC 28 2012 TYPE: Regional WHO: NCEP, NWSTG, NCF, NWS SOUTHERN/EASTERN REGIONS REASON: Severe weather and tornado potential across portions of Southern Region Christmas Day and Christmas night evolving into a significant winter storm over Eastern Region Wednesday through early Friday. Link to comment Share on other sites More sharing options...
Ground Scouring Posted December 25, 2012 Share Posted December 25, 2012 The 00Z soundings from KBRO and MMVR (Veracruz, Mexico) are coming in much more on the dry adiabatic side than even the 00Z NAM forecasted...indicating a very robust dry punch that will likely evolve much as the NAM and WRF indicate, perhaps even more significantly. This would cut down on morning convection tomorrow and really substantiate the impetus for a High Risk. As far as my comparison to 04/27/2011 goes...thanks to CUmet for realizing that I meant a watered-down (but still very severe) version. (It will certainly be bigger than 12/23/2002, which had no significant tornadoes.) Merry Christmas to all Dixie Alley residents...be ready for this. Link to comment Share on other sites More sharing options...
andyhb Posted December 25, 2012 Share Posted December 25, 2012 Newest RAP is popping 3 km EHI's of 6-8 over NOLA by 21z tomorrow...with large curved/looping hodographs easily supportive of strong to violent tornadoes. Link to comment Share on other sites More sharing options...
Ground Scouring Posted December 25, 2012 Share Posted December 25, 2012 Most similar to 01/17/2010 in terms of shear-based parameters and the dry slot, but the upper-air pattern is more progressive, the instability far greater, and the dry slot more significant in this case. Vertical shear is also greater in the upcoming system. Few other analogs matched the precise upper-level pattern in this case; even the 01/17/2010 case does not depict as strong a Pacific NW shortwave and a pattern as progressive as in the upcoming case (in which the shortwave Rockies ridge will be less pronounced). http://www.eas.slu.edu/CIPS/ANALOG/stats.php?reg=SE&model=NAM212&fhr=F036&flg= http://www.eas.slu.edu/CIPS/ANALOG/event.php?reg=SE&fhr=F036&model=NAM212&dt=2010011712 Link to comment Share on other sites More sharing options...
andyhb Posted December 25, 2012 Share Posted December 25, 2012 Moderate Risk D1: DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1200 AM CST TUE DEC 25 2012 VALID 251200Z - 261200Z ...THERE IS A MDT RISK OF SVR TSTMS ACROSS SOUTHEAST TX AND PORTIONS OF LA/MS/AL/FL PANHANDLE... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE GULF COAST/SOUTHEAST STATES... ...A DANGEROUS CHRISTMAS DAY/NIGHT SEVERE WEATHER EPISODE IS LIKELY TO UNFOLD...INCLUDING THE POTENTIAL FOR STRONG TORNADOES AND WIDESPREAD DAMAGING WINDS...ACROSS PORTIONS OF THE GULF COAST REGION AND LOWER MS RIVER VALLEY... ..SYNOPSIS A PROGRESSIVE LARGE SCALE FLOW PATTERN WILL PREVAIL OVER THE CONUS DURING THE PERIOD. THE PRIMARY SYSTEM OF FOCUS WITH RESPECT TO DEEP CONVECTION WILL BE A VIGOROUS SHORTWAVE TROUGH /AND ASSOCIATED STRONG UPPER JET STREAK/ AS IT SPREADS EASTWARD...AMPLIFIES...AND THEN BECOMES INCREASINGLY CLOSED/NEGATIVELY TILTED TONIGHT AS IT ADVANCES FROM THE SOUTHERN PLAINS TO THE LOWER MS VALLEY/TN VALLEY. ..GULF COAST REGION/LOWER MS VALLEY TO SOUTHEAST STATES GIVEN THE LARGE SCALE SCENARIO AS PREVIOUSLY DESCRIBED...A SURFACE LOW IS EXPECTED TO STEADILY DEEPEN AS IT SPREADS NORTHEASTWARD FROM SOUTHEAST TX THIS MORNING TO THE TN VALLEY TONIGHT. AS THIS OCCURS...AN INCREASINGLY MOIST LOW-LEVEL AIRMASS WILL DEVELOP NORTHWARD IN TANDEM WITH A WEST-EAST ORIENTED WARM FRONT...WITH LOWER 60S DEWPOINTS /AND SOME MIDDLE 60S F NEAR THE COAST/ BECOMING INCREASINGLY PREVALENT WITHIN THE WARM SECTOR. INITIALLY...STRONG/POTENTIALLY SEVERE TSTMS ARE EXPECTED TO BE ONGOING THIS MORNING...ESPECIALLY ACROSS SOUTHEAST TX INTO LA. THIS INCLUDES THE POSSIBILITY OF ELEVATED SUPERCELLS NORTH OF THE WARM FRONT /MAINLY CAPABLE OF HAIL/...ALONG WITH AN INCREASING SURFACE BASED SEVERE THREAT NEAR/SOUTH OF THE WARM FRONT THIS MORNING ACROSS THE UPPER TX COAST/SOUTHERN LA. WITHIN AN INCREASINGLY MOIST AND HIGHLY SHEARED ENVIRONMENT...THIS INCLUDES THE POSSIBILITY OF AN EARLY DAY TORNADO/WIND DAMAGE THREAT THIS MORNING/EARLY AFTERNOON ACROSS SOUTHEAST TX INTO SOUTHERN LA. WITH TIME...THE AIRMASS WILL FURTHER DESTABILIZE INTO THIS AFTERNOON ESPECIALLY ACROSS CENTRAL/SOUTHERN LA AND SOUTHERN PORTIONS OF MS/AL...WITH 1000+ J/KG MLCAPE FOR AREAS WITHIN 150-200 MILES OF THE GULF COAST. LESSER...AND A BIT MORE UNCERTAIN...DESTABILIZATION IS EXPECTED CLOSER TO THE EAST-NORTHEASTWARD SURFACE LOW LATER TODAY/TONIGHT...LARGELY OWING TO PERSISTENT PRECIPITATION NEAR/NORTH OF THE WARM FRONT AND A LESSER INFLUX OF LOW-LEVEL MOISTURE. REGARDLESS...THIS DESTABILIZATION COUPLED WITH AN INCREASINGLY STRONG DEEP LAYER WIND FIELD...WITH 70-100 KT AT 500 MB AND 110+ KT AT 250 MB...WILL RESULT IN DEEP LAYER SHEAR SUPPORTIVE OF ROTATING UPDRAFTS/SUPERCELLS. ACCENTUATED BY THE DEEPENING PHASE OF THE CYCLONE...EVENTUAL QLCS DEVELOPMENT SEEMS LIKELY TO OCCUR THIS AFTERNOON INTO TONIGHT NEAR/AHEAD OF THE EASTWARD-ADVANCING COLD FRONT...ALTHOUGH DISCRETE SUPERCELLS WILL REMAIN POSSIBLE WITHIN THE WARM SECTOR AND NEAR/IMMEDIATELY AHEAD OF THE EVOLVING QLCS...WHICH SEEMS LIKELY TO CROSS LA AND THE SOUTHERN HALVES OF MS/AL THROUGH TONIGHT. POTENTIALLY WIDESPREAD DAMAGING WINDS WILL BE POSSIBLE WITH SUSTAINED BOWING SEGMENTS. FURTHERMORE...A FEW STRONG/POTENTIALLY LONG-LIVED TORNADOES WILL ALSO BE POSSIBLE WITH DISCRETE SUPERCELLS AND/OR EVENTUAL EMBEDDED MESO-VORTICES LATER THIS AFTERNOON/TONIGHT...ESPECIALLY GIVEN 200-500 M2/S2 0-1 KM SRH COINCIDENT WITH A 50-70 KT LOW LEVEL JET LATE THIS AFTERNOON/TONIGHT. WHILE THE OVERALL SYSTEM STRENGTHENS...INSTABILITY WILL WANE LATE IN THE PERIOD. EVEN SO...A SEVERE THREAT MAY REACH AS FAR EAST AS PARTS OF AL...SOUTHEAST TN...AND WESTERN GA LATER TONIGHT...WITH SOME POTENTIAL FOR AREAS INCLUDING COASTAL SC BY THE EARLY MORNING HOURS OF WEDNESDAY. ..GUYER/SMITH.. 12/25/2012 Link to comment Share on other sites More sharing options...
ksstormhunter Posted December 25, 2012 Share Posted December 25, 2012 SmartCast Analysis for 25 Dec/05Z to 26 Dec 05Z ( Base on my model output only) Update.... First the winter side of the storm system: Currently Targeting the area of Tinker to McAlester this hour. My model showing the heaviest snow along this corridor. McAlester Region: Tracking the snow to begin around 18Z, with periods of heavy snow, with snowfall rates of 1.3” per hour. In addition, winds look to increase to around 30MPH along the same timeframe, so look for blowing snow. Right now looking at 7.9” of snow in this area. Tinker AFB/OKC Region: Showing a period of mixed precip from 06Z to 11Z, then changing to all snow by 12Z. Looking at visibilities down to less than ½ mile, and snowfall rates of up to 1.1” per hour possible. Right now looking max of 5.7” of snow accumulation in this area. This is down from 7.1” prediction on the 01Z run. In addition, looking at winds gusting to 35 to 40mph, which will create temporary blizzard conditions in this area. Vance AFB Region: Looking to be on the fringe of the snow, but still looking at 3.5” of snow possible. Snow will begin around 09Z, and will be heaviest from 16Z to 20Z. In addition, winds will be gusting up to 35MPH during this time, so look for reduce visibility and blowing snow. Dallas Region: Tracking some strong thunderstorms pushing through the area from 16Z to 21Z, then changing to snow, with a potential for localized 1-2” across the area. In addition, looking at winds gusting up to 44MPH from 22Z to 04Z. Damaging Wind Potential: Hobart, Lawton, Lubbock, Childress, and Clinton are all targeted for winds 45 to 50MPH winds during the next 24 hours. In addition, looking at snowfall from 1” to 3” possible. This will also cause tempo conditions of reduce vis and blowing snow. Severe Wx Potential: 05Z SmartCast run is zoningin on the Lake Charles region, with a 76% of some tornadic event within the area. In addition, forecasted hail projected around 2.3” to 2.6” and convective winds of 55 to 68MPH Possible. In addition, heavy rainfall is possible in these areas with precip totals of 1.3 to 1.9” possible. Link to comment Share on other sites More sharing options...
Ground Scouring Posted December 25, 2012 Share Posted December 25, 2012 Are there any factors re: the deepening rate of the surface low which may have prevented SPC from selecting a higher TOR probability than 15%? Perhaps a weaker cyclone is expected in the short term (06-12Z Tuesday) which would fail to mix out the boundary layer as efficiently as a stronger low-level wind profile would. I am just trying to account for the reasons as to why SPC would give more weight to morning junk convection in this case given the dry punch lurking to the south. Link to comment Share on other sites More sharing options...
andyhb Posted December 25, 2012 Share Posted December 25, 2012 Are there any factors re: the deepening rate of the surface low which may have prevented SPC from selecting a higher TOR probability than 15%? Perhaps a weaker cyclone is expected in the short term (06-12Z Tuesday) which would fail to mix out the boundary layer as efficiently as a stronger low-level wind profile would. I am just trying to account for the reasons as to why SPC would give more weight to morning junk convection in this case given the dry punch lurking to the south. I just think they are trying to wait before mesoscale details are ironed out a bit further and, as you mentioned, the junk convection situation becomes more apparent until a possible upgrade, that was a pretty strongly worded moderate, although I am a bit surprised there was no mention of an upgrade to high (although that didn't happen on March 2nd this year so I suppose that doesn't mean that much). Link to comment Share on other sites More sharing options...
tmagan Posted December 25, 2012 Share Posted December 25, 2012 Jackson, MS RAP BUFKIT forecast sounding valid 23Z 25 December. Link to comment Share on other sites More sharing options...
Srain Posted December 25, 2012 Share Posted December 25, 2012 SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX 1247 AM CST TUE DEC 25 2012 TXZ177-198-199-212-250715- WALLER TX-WALKER TX-MONTGOMERY TX-GRIMES TX- 1247 AM CST TUE DEC 25 2012 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN WALLER... SOUTHWESTERN WALKER...NORTHWESTERN MONTGOMERY AND SOUTHEASTERN GRIMES COUNTIES UNTIL 115 AM CST... AT 1244 AM CST...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING STRONG THUNDERSTORMS NEAR MAGNOLIA...OR 9 MILES NORTHWEST OF PINEHURST...MOVING NORTHEAST AT 40 MPH. HAIL UP TO THE SIZE OF DIMES AND WIND GUSTS UP TO 40 MPH WILL BE POSSIBLE WITH THIS STORM. LOCATIONS IMPACTED INCLUDE... PINEHURST...MAGNOLIA...NEW WAVERLY...MONTGOMERY AND TODD MISSION. Link to comment Share on other sites More sharing options...
SmokeEater Posted December 25, 2012 Share Posted December 25, 2012 Cell NW of Houston hitting 40,000 feet already. Link to comment Share on other sites More sharing options...
Superstorm93 Posted December 25, 2012 Share Posted December 25, 2012 Things are starting to kick up along that warm front. MUCAPE and MLCAPE are slowly increasing as well as SRH. Link to comment Share on other sites More sharing options...
andyhb Posted December 25, 2012 Share Posted December 25, 2012 Cell coming off the water near Lake Charles may have potential for large hail. Link to comment Share on other sites More sharing options...
Srain Posted December 25, 2012 Share Posted December 25, 2012 MESOSCALE DISCUSSION 2203 NWS STORM PREDICTION CENTER NORMAN OK 0101 AM CST TUE DEC 25 2012 AREAS AFFECTED...PORTIONS OF CENTRAL/ERN TX...WRN LA CONCERNING...SEVERE POTENTIAL...WATCH LIKELY VALID 250701Z - 250800Z PROBABILITY OF WATCH ISSUANCE...80 PERCENT SUMMARY...TSTMS WILL CONTINUE TO DEVELOP/INTENSIFY NORTH OF A WARM FRONT THROUGH THE EARLY MORNING HOURS. SUPERCELL TSTMS ARE LIKELY WITH LARGE HAIL POSING THE PRIMARY THREAT. A WW IS LIKELY PRIOR TO 08Z. DISCUSSION...TSTMS ARE DEVELOPING/INTENSIFYING NORTH OF A WARM FRONT THAT WAS LOCATED FROM COT NEWD TO JUST NW OF HOU TO NORTH OF BPT AT 06Z. THIS DEVELOPMENT IS IN RESPONSE TO INCREASING WAA IN ADVANCE OF AN INTENSE SEWD-MOVING SHORTWAVE APCHG W TX. THE ENVIRONMENT NORTH OF THE WARM FRONT IS CHARACTERIZED BY 40-45 KT DEEP LAYER SHEAR THAT IS FORECAST TO INCREASE TO 55-60 KT BY 12Z. MUCAPES OF 1000-1500 J/KG WILL SUPPORT ELEVATED SUPERCELLS WITH A THREAT OF LARGE HAIL. STORMS ARE EXPECTED TO INCREASE IN COVERAGE AND INTENSITY OVER THE NEXT FEW HOURS AND A SVR TSTM WATCH WILL LIKELY BE NEEDED BY 08Z. ..BUNTING/MEAD.. 12/25/2012 ATTN...WFO...LCH...SHV...HGX...FWD...EWX... Link to comment Share on other sites More sharing options...
hm8 Posted December 25, 2012 Share Posted December 25, 2012 Link to comment Share on other sites More sharing options...
andyhb Posted December 25, 2012 Share Posted December 25, 2012 Yeah, that thing is a monster on the WRF there. Link to comment Share on other sites More sharing options...
tornadotony Posted December 25, 2012 Share Posted December 25, 2012 The 00z 4km NMM is a lot more impressive than the 12z, too: http://www.emc.ncep....yle/spcprod/00/ I think it has to do with the farther S low position. Get that low farther south and back the winds, you also change the direction of the bulk shear vector to a more zonal direction, meaning that it will be more perpendicular to the boundary. Link to comment Share on other sites More sharing options...
ksstormhunter Posted December 25, 2012 Share Posted December 25, 2012 Just got in touch with some fellow military guys in Oklahoma City area, been getting Freezing Rain over past 60-90 minutes. Many of the bridges are already ice covered. Mulitple accidents already across the city. That area of Freezing precip is spreading NE towards the Tulsa region. Link to comment Share on other sites More sharing options...
SouthernNJ Posted December 25, 2012 Share Posted December 25, 2012 Jennings LA about to see a supercell with some good hail. Link to comment Share on other sites More sharing options...
andyhb Posted December 25, 2012 Share Posted December 25, 2012 Warm front has already retreated to I-10 in LA. Link to comment Share on other sites More sharing options...
thewxmann Posted December 25, 2012 Share Posted December 25, 2012 Holy crap, the RAP. Link to comment Share on other sites More sharing options...
andyhb Posted December 25, 2012 Share Posted December 25, 2012 Holy crap, the RAP. Nice rhymes, but yeah it's not looking pretty. The hodographs are simply insane. Link to comment Share on other sites More sharing options...
Ed Lizard Posted December 25, 2012 Share Posted December 25, 2012 Jennings LA about to see a supercell with some good hail. BULLETIN - EAS ACTIVATION REQUESTED TORNADO WARNING NATIONAL WEATHER SERVICE LAKE CHARLES LA 239 AM CST TUE DEC 25 2012 THE NATIONAL WEATHER SERVICE IN LAKE CHARLES HAS ISSUED A * TORNADO WARNING FOR... NORTHERN ACADIA PARISH IN SOUTHWEST LOUISIANA... THIS INCLUDES...MERMENTAU...IOTA... EAST CENTRAL JEFFERSON DAVIS PARISH IN SOUTHWEST LOUISIANA... THIS INCLUDES JENNINGS... * UNTIL 315 AM CST * AT 236 AM CST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR JENNINGS... MOVING NORTHEAST AT 30 MPH. * THE TORNADO WILL BE NEAR... MERMENTAU BY 245 AM CST... EVANGELINE BY 250 AM CST... EGAN BY 255 AM CST... IOTA BY 305 AM CST... MAXIE BY 310 AM CST... MOWATA BY 315 AM CST... Link to comment Share on other sites More sharing options...
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