AMS: National Meeting: Strong to severe thunderstorms / Heavy rain ?

[OKpowdah]

Happy New Year everyone!!

This is a shot in the dark, and I haven't looked much into it besides following the model run output, but man that would be pretty cool if the AMS conference in Austin, TX was interrupted Tuesday or Wednesday evening by strong thunderstorms in TX and OK.

*** This is 8 days out right now ***

However, BOTH the GFS and Euro have been barreling a potent shortwave trough through the TX and OK next week.

General pattern trend for this week into next: Developing +NAO/+AO ... and general positive annular mode, but with the polar vortex leaning towards North America ... this means Canada may get cold but the CONUS is about to get a thaw. Zonal jet lifts north toward the national border.

GFS and Euro both take a piece of energy from the Pacific jet, drop it south toward Baja California as a closed low, then a larger trough dips down in the East Pacific and kicks the low eastward into the southern Plains.

Something to keep an eye on anyway just for fun. I'll get into more specifics maybe in the next couple days on the interacting features at play.

[andyhb]

Nice to see that this boring pattern may be short lived (knock on wood).

[Buckeye05]

Glad to to at least have something to watch, even if its this far out.

[andyhb]

I have a feeling the moisture return may be limited for this first shortwave here, however, should something develop afterwards, it could have an unseasonably moist warm sector to work with.

[Minnesota Meso]

I have a feeling the moisture return may be limited for this first shortwave here, however, should something develop afterwards, it could have an unseasonably moist warm sector to work with.

 

it appears at this time that the low level jet will be strong but will originate near the Texas/Mexico border and miss the opportunity to fetch moisture out of the gulf.

[Minnesota Meso]

 

 

 

 

[Ed Lizard]

Just seeing 12Z Euro,  the event is probably past by Thursday morning, but a nice looking trough and a 40 or 40 knot 850 mb jet between Wednesday and Thursday at 12Z (6 am) showing on Euro.  Won't have PPV AccuWx graphics for another hour or three, but the 12Z Thursday Euro, while the juicy part has probably moved past into Louisiana, turning with height between surface and 500 mb, a strong LLJ and a decent trough.  Fun-derstorms, anyone?

 

[OKpowdah]

I think it looks like the consensus has shifted to a Wednesday event at this point. Have to keep in mind the tendency of all model guidance (in particular the Euro) to eject cut-off lows eastward too quickly.

 

 

Not too shabby...

 

[andyhb]

The latest Euro/GFS runs seem to suggest something afterwards with another strong Pacific jet streak diving into the coast following this first trough, that will need to be watched, especially if we get this s/w to act as a moisture pump.

[andyhb]

Nice to see the drought-busting potential this thing has across TX, even with the drought much less severe across the state that it once was, some areas are still pretty parched.

[Buckeye05]

06z GFS looks decent in regards to severe (more of a Dixie threat though).

[Srain]

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
102 AM EST THU JAN 03 2013

VALID 12Z SUN JAN 06 2013 - 12Z THU JAN 10 2013

...SOUTHERN STREAM EXPECTED TO BECOME AN ACTIVE WEATHER MAKER BY
MIDDLE OF NEXT WEEK...

FEW CHANGES OVERALL TO THE FORECAST PHILOSOPHY FROM YESTERDAY. THE
MEDIUM RANGE FORECASTS AND SPLIT-FLOW PATTERN CONTINUES TO BE
HANDLED REASONABLY WELL. IN FACT...THE OPERATIONAL 2/12Z GFS AND
2/12Z ECMWF WERE PREFERRED 50/50 BLEND THROUGH DAY 5.

NORTHERN STREAM FLOW SHOULD REMAIN PROGRESSIVE WITH RESPECT TO THE
DEVELOPMENT OF SURFACE WAVES MIGRATING ACROSS SOUTHERN
CANADA...AND WITH A MODERATE 'KICKER' WAVE ENTERING THE PACIFIC
NORTHWEST ON DAY 6. THE 2/12Z ECMWF ENSEMBLE MEAN WAS A GOOD
APPROXIMATION OF THE OVERALL FLOW PATTERN...AND IN
PARTICULAR...WITH A SOUTHERN STREAM SYSTEM EJECTING OUT OF THE
SOUTHERN HIGH PLAINS FROM DAY 5 TO DAY 7. MEDIUM RANGE GRAPHICS
BEGIN TRACKING A MODERATE CYCLONE NORTHEASTWARD ACROSS THE
SOUTHERN ROCKIES AND SOUTH CENTRAL PLAINS BY DAY 6 AND INTO THE
MIDWEST ON DAY 7. THE ECMWF ENSEMBLES WERE GIVEN HIGHER WEIGHTING
(60%) FOR THE DAY 6-7 PERIOD TO MITIGATE THE TIMING DIFFERENCES
PRESENTED BY THE OPERATIONAL 12Z GFS/ECMWF.

ITS SOLUTION ALOFT (THE ECMWF ENSEMBLE MEAN) IS A GOOD MIDDLE
GROUND FOR THE PROGRESSION OF THE SOUTHERN STREAM SYSTEM...BEING
FASTER THAN THE PREVIOUS 2 OPERATIONAL EC RUNS (2/12Z-2/00Z)
ACROSS SOUTHERN CA/AZ AND A TAD SLOWER THAN THE PREVIOUS 2
OPERATIONAL GFS RUNS (2/12Z-3/00Z) ACROSS NM AND TX/OK. DID SEE
SOME MERIT IN USING THE 12Z OPERATIONAL GFS/ECMWF (20%/20%) FOR
DAY 6-7...TO HANDLE THE SURFACE DETAILS IN BOTH THE NORTHERN AND
SOUTHERN STREAM ACROSS NORTH AMERICA. THE 3/00Z GFS LOOKED TOO
FAST AND WAS A SOUTHERN OUTLIER BY LATE DAY 6 INTO DAY 7 ACROSS
NORTHERN TEXAS.
 

[Ed Lizard]

I went to college in Austin.  Day of my engineering economics final, could actually watch TCu bubbling up from campus, and next day in NW Austin went to see a movie, parking lot full of trashed cars.  Massive hail.  KVUE Channel 24 has awesome video of a raccoon running for cover in the parking lot on the evening news.  Of course, that was May.  But I recall, think it was 1990, about February 1, a severe t-storm stripped some of the black copper (it was supposed to oxidize to burnt orange, never did) off the RTF building.  ETA - 53 mph gust at AUS, I do remember this day.

 

Hoping AUS gives the AMS folks something to remember.

 

Euro PPV showing area of greater than 500 J/Kg CAPE over I-35 corridor area at 0Z Wednesday (Tuesday evening) and shows impressive rains (well over an inch) 12 hours between 0Z WEdnesday and 12Z Wednesday on the PPV between AUS and HOU.  As far as wind energy, low level jet, and turning with height, I'll let the free Euro do the talking.

 

 

 

 

[andyhb]

The further south ideas on the 00z GGEM/Euro may be more conducive to a severe threat across portions of Southern/Central TX.

[Dsnowx53]

The 18z GFS might allow for things to get pretty interesting for Austin. 

 

[Srain]

It’s time to start focusing on the next storm system in more detail which has a potential to be a high impact event for our Region. The 12Z suite of ensembles are in and while there remain some uncertainty on the eventual track and timing, it does appear the threat of a Winter Storm with both wintry and severe elements may well have an effect on New Mexico/Texas/Oklahoma into Louisiana. At this time the on set of this developing storm would be Monday to our W across New Mexico and Tuesday into Wednesday depending on which solution ends up being more correct. We will need to keep an eye for development over the weekend into early next week as there are strong signals that a very potent dynamic Winter Storm will have an impact, be it wintry or severe.

[andyhb]

Euro, as I mentioned in the TX thread, would have good potential for severe Tuesday evening into Wednesday morning, with adequate thermos and some strong low level wind profiles.

[SquatchinNY]

This will be another test for my Radarscope, which performed well with DEC/25.

[Srain]

The overnight guidance continues to advertise a very potent storm system crossing Northern Mexico at the 500mb level. The trends are for the 5H Low to close off over West Texas and meander ENE as a surface low develops near Corpus Christi and rides ENE toward SE TX. The HPC has increased the QPF for Central & East Texas to the 3-4 inch range with isolated higher amounts if training develops. The SPC has outlined a large portion of Texas and possibly extending into Western Louisiana as well. While some uncertainty remains regarding timing, the trends suggest a very stormy Tuesday into Wednesday with severe storms possible as well as Flash Flooding across Central and East Texas.

[Srain]

The 12Z GFS is suggesting a very potent Winter Storm with both severe and wintry elements as the 500mb low deepens across Texas and meandering ENE. The GFS also is suggesting a rather deep surface Coastal Low develops and heads ENE across SE TX into SW LA providing for heavy storms and training potentially flooding rainfall over parts of Central/East Texas into Louisiana. As the upper low strengthens, wrap around moisture of the wintry variety breaks out N of the cold core low across the Panhandle and the Red River Valley possibly into Oklahoma.

 

 

 

 

 

 

[Ed Lizard]

DAY 4-8 CONVECTIVE OUTLOOK 

   NWS STORM PREDICTION CENTER NORMAN OK

   0308 AM CST SAT JAN 05 2013

  

   VALID 081200Z - 131200Z

  

   ...DISCUSSION...

   THERE IS INCREASING CONFIDENCE THAT A SIGNIFICANT UPPER LOW WILL

   BEGIN TO EJECT EWD ACROSS NRN MEXICO INTO SOUTH TX DURING THE DAY4-5

   TIME FRAME.  HOWEVER...THE GFS IS CONSIDERABLY FASTER THAN THE ECMWF

   AS IT MOVES THE CENTER OF THE UPPER LOW INTO CNTRL TX BY 09/12Z

   WHILE THE ECMWF IS NEARLY 300 MI WEST OF THIS LOCATION OVER THE BIG

   BEND REGION.  WHILE STRONG MID LEVEL FLOW SHOULD ROTATE THROUGH THE

   BASE OF THE TROUGH INTO EAST TX AT SOME POINT IT/S NOT ENTIRELY

   CLEAR WHEN THIS WILL OCCUR.  ADDITIONALLY...THE PROSPECT FOR

   MEANINGFUL DESTABILIZATION INLAND MAY BE IMPEDED BY SUBSTANTIAL

   PRECIPITATION WITHIN THE WARM CONVEYOR.  GIVEN THE TIMING

   DIFFERENCES AND POSSIBLE DESTABILIZATION ISSUES WILL NOT OUTLOOK AN

   ORGANIZED SEVERE AREA MID WEEK ACROSS TX INTO THE LOWER MS VALLEY.

   HOWEVER LATER MODEL GUIDANCE MAY PROVIDE MORE CLARITY WHICH COULD

   LEAD TO SEVERE PROBS ADDED FOR PORTIONS OF THIS REGION.

  

   ..DARROW.. 01/05/2013

 

[Srain]

HPC Model Diagnostic Discussion concerning the storm next week:

 

...SRN STREAM SHRTWV TROF AND DEVELOPING CLSD LOW OVER THE
SOUTHWEST...
 
PREFERENCE: 12Z ECMWF/00Z ECENS MEAN BLEND
CONFIDENCE: ABOVE AVERAGE
 
THE 12Z NAM ALONG WITH THE 12Z GFS...12Z UKMET AND 12Z GEM GLOBAL
CONTINUE TO TREND TWD A ECMWF/ECENS MEAN LED CONSENSUS SOLN WITH A
DEEP CLSD LOW DIGGING SEWD ACRS CA AND INTO THE SOUTHWEST U.S. BY
LATE SUN...AND THEN SLOWLY ADVANCING DOWN INTO NRN MEXICO WEST OF
THE BIG BEND OF TX BY LATE TUE. THE ECMWF AND TO A LESSER EXTENT
THE UKMET HAVE BEEN VERY CONSISTENT WHEN COMPARED TO THE
GFS/NAM/GEM GLOBAL SOLNS IN HANDLING THIS SRN STREAM ENERGY WITHIN
A LARGER SCALE SPLIT FLOW REGIME. WILL FAVOR A ECMWF/ECENS MEAN
BLEND BASED ON THEIR EXCELLENT RUN TO RUN CONTINUITY.

[Ed Lizard]

With Euro 6 hour temps in SETX pushing near 20 Celcius (hmmm, new computer alt 0186 for a degree sign works on some web sites, not others, 6 hour text guidance available on AccuWx PPV, no maps for another 90 minutes or so...) later during the day, a possible 50 knot 850 mb jet could be a positive sign for severe, maybe even surface based, in SETX.  IAH numbers, 2 inches of rain warmer than 16C (60F) which in January could be surface or near surface.

 

 

[SquatchinNY]

Thanks for the updates guys

[Ed Lizard]

GFS coming towards slower European.  Heavy rain, maybe, but the saturated surface to 200 mb, low lapse rate, minimal cape 1.9" PW in January on the GFS forecast sounding for IAH Wednesday evening, I just don't know.  Wasted shear/helicity.   IMBYism. 

 

 

South Texas earlier in the day might be a little more exciting.  Alice at 6 am is near 1000 J/Kg CAPE, although very little below 850 mb, with decent helicity per NIU sounder, and it looks like there might be enough instability from the Southwestern HOU suburbs down along the coastal bend for decent storms.  But w/ 3 inch storm totals common along and East of the I-35 corridor, might be more rain/local flooding than severe.

 

Glass half full optimistic, last January 9 was also a low CAPE, high shear day with the benefit of LCLs and it worked out.

 

BTW, 1.9 or 2 inch PW, if it verifies, might be some kind of record for the date.  Not sure if anyone actually keeps records.

 

 

 

[andyhb]

We have a D3 slight and a D4 outlook from SPC:

 

DAY 3 CONVECTIVE OUTLOOK     NWS STORM PREDICTION CENTER NORMAN OK   0221 AM CST SUN JAN 06 2013      VALID 081200Z - 091200Z      ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SOUTH TX...      ...TX...      LATEST SHORT-RANGE MODEL GUIDANCE CONTINUES TO SUGGEST UPPER LOW   OVER NRN MEXICO WILL BEGIN TO EJECT EWD DURING THE DAY3 PERIOD AS   MID LEVEL SPEED MAX ROTATES TOWARD THE MIDDLE RIO GRANDE RIVER   VALLEY LATE.  IN RESPONSE TO THIS FEATURE IT APPEARS LOW LEVEL   TRAJECTORIES WILL BECOME FAVORABLE FOR NWD ADVANCEMENT OF MARITIME   TROPICAL AIRMASS ACROSS DEEP SOUTH TX/LOWER TX COAST.  AS SFC DEW   POINTS RISE INTO THE UPPER 60S THERMODYNAMIC PROFILES SHOULD BECOME   INCREASINGLY FAVORABLE FOR SFC-BASED CONVECTION WITHIN A SHEARED   ENVIRONMENT INCREASINGLY FAVORABLE FOR SUSTAINED ROTATING UPDRAFTS.    AS COASTAL/WARM FRONT ADVANCES INLAND BUOYANCY SHOULD INCREASE SUCH   THAT ISOLATED SUPERCELLS ARE POSSIBLE...BOTH ACROSS THE WARM SECTOR   AND PERHAPS JUST NORTH OF THE FRONT WHERE STRONG LOW-MID LEVEL SHEAR   WILL BE PRESENT.  STRENGTHENING LLJ AHEAD OF THE PACIFIC FRONT WILL   ENCOURAGE A SUBSTANTIAL AMOUNT OF CONVECTION/PRECIPITATION ACROSS TX   WITH TSTM ACTIVITY ACROSS CNTRL/NRN TX ELEVATED AND LESS BUOYANT IN   NATURE.  ISOLATED TORNADOES MAY OCCUR WITH NEAR-SFC BASED ACTIVITY   AND MARGINALLY SEVERE HAIL MAY ALSO ACCOMPANY THE STRONGEST   CONVECTION.  NWD EXTENT OF SEVERE WILL BE LIMITED BY COOLER BOUNDARY   LAYER CONDITIONS ASSOCIATED WITH SUBSTANTIAL PRECIPITATION BENEATH   THE WARM CONVEYOR.      ..DARROW.. 01/06/2013

 

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0313 AM CST SUN JAN 06 2013

VALID 091200Z - 141200Z

...DISCUSSION...
CONSIDERABLE DISCREPANCY BEGINS TO EMERGE DURING THE MEDIUM RANGE
PERIOD REGARDING THE EJECTING UPPER LOW ACROSS TX. THE GFS IS
SUBSTANTIALLY FASTER AND FARTHER NORTH THAN THE ECMWF BY DAY5 WITH A
DEAMPLIFYING SHORT-WAVE OVER SERN ONTARIO AT 11/12Z WHILE THE ECMWF
MAINTAINS A CLOSED LOWER NEAR THE ARKLATEX. FOR THIS REASON EXTREME
UNCERTAINTY REGARDING SEVERE EXISTS BEYOND WEDNESDAY.

DURING THE DAY4 PERIOD THERE IS SUFFICIENT CONFIDENCE REGARDING THE
POTENTIAL FOR STRONG THUNDERSTORM DEVELOPMENT ACROSS THE COASTAL
PLAINS OF TX WHERE AMPLE LOW LEVEL MOISTURE WILL HAVE SPREAD INLAND
PRIOR TO THE ARRIVAL OF STRONG MID LEVEL SPEED MAX AHEAD OF PACIFIC
FRONT. IT APPEARS A SUPERCELL ENVIRONMENT WILL EXIST ACROSS THE
AFOREMENTIONED REGION AND LARGE SCALE FORCING SHOULD SUPPORT TSTM
DEVELOPMENT.

..DARROW.. 01/06/2013

 

[Srain]

Worrisome to see QPF for areas E of HWY 281 or just W of Austin along the Balcones Escarpment into SE TX/Western Louisiana in the 4-6 inch range. Training appears likely along and E of the warm front with PW's 2 Standard Deviations+ above normal for the Region. I expect Flash Flood Watches to be hoisted and the HPC has outlined the area for a Slight Risk of Excessive Rainfall for Day 3.

[Srain]

I'll also mention the wintry side potential of this potent Storm System. This storm will likely be a very dynamic with a closed cold core 5H low that is slow moving. A trowal appears likely across portions of the Panhandle Regions of TX/OK extending WSW into Eastern New Mexico bringing impressive heavy wet snow fall to Roswell/Ruidoso/Carlsbad/Hobbs and possibly into Lubbock as well depending on the eventual storm track and speed. The GFS has been on the progressive side, but has trended toward the slower much stronger Euro solution. As we have seen in the current pattern of the last couple of weeks, the European guidance has been more correct and has slowed the progression of these closed 5H low traversing across Northern Mexico.

[heavy_wx]

Worrisome to see QPF for areas E of HWY 281 or just W of Austin along the Balcones Escarpment into SE TX/Western Louisiana in the 4-6 inch range. Training appears likely along and E of the warm front with PW's 2 Standard Deviations+ above normal for the Region. I expect Flash Flood Watches to be hoisted and the HPC has outlined the area for a Slight Risk of Excessive Rainfall for Day 3.

 

The 06z GFS suggests the possibility of some training with a fairly slow MBE velocity of 9 kts around 18z Wednesday for KAUS. It also shows PW values between 1.50" and 1.75" for much of Wednesday, further indicating the heavy rain potential.

 

[Srain]

Morning e-mail from Jeff: (Pro Met: Harris County Flood Control District)

 

Increasing potential for widespread heavy rainfall and severe weather Tues-Thurs.
 
A powerful upper level storm system currently of the California coast will bring high impact weather to much of the state of TX this week.
 
Discussion:
The potent upper level system will dig SE into N MX over the next 24 hours resulting in the activation of the cold frontal boundary over the western Gulf of Mexico. This front will begin to return northward as a warm front, while above the surface strong moisture advection brings clouds and developing rainfall rapidly northward off the western Gulf by late Monday night. This is in response to deepen moisture profiles and increasing large scale lift. The powerful upper level storm moves into and across TX from the Big Bend area toward NC TX on Tues-Thurs. Surface low pressure will form somewhere over the lower Rio Grande plains and track ENE to NE across SC into EC TX Tues-Wed bringing a warm front northward over nearly all of SE TX. Widespread heavy rainfall is likely with this set up along with sporadic severe weather.

 

Heavy Rainfall/Flood Threat:
Models and HPC QPF guidance is really pegging the area with some large totals. Moisture level do increase significantly late Monday into Tuesday with PWS approaching 1.6-1.8 inches on Tuesday….which is above +2SD of normal for early January and at or above maximum expected values. This alone raises a warning flag for excessive rainfall, but combine those moisture levels with sustained lift and surface boundaries such as a warm front or slow moving cold front and the potential for flooding rainfall increases. Forecast soundings show a nearly saturated air column by Tuesday afternoon suggesting efficient rainfall processes…or high rainfall rates. Model guidance has been fairly consistent on the placement of amounts of rainfall with this event.
 
Expect widespread 2-4 inches across much of the area with isolated totals of 4-6 inches possible. Given already moist to wet grounds much of this rainfall is going to run-off. Additionally hourly rainfall rates under the stronger storms may average 1-3 inches suggesting a higher urban flooding threat. With the upper level system slowing as it moves into TX, the threat for training thunderstorms will be increasing and be prolonged from late Tuesday into Wednesday evening. Significant rises on area watersheds appears likely with the amount of rainfall forecasted.

 

A Flash Flood Watch will likely be required if forecasted rainfall amounts continue to look likely.
 
Severe Weather:
This system will be highly dynamic with a well defined warm sector spreading inland over the TX coastal plains overspread by strong winds aloft. Track of the surface low will be important for defining where the greatest severe weather threat will reside…best determination at this time is for the surface low to track from near Laredo toward College Station and then toward NW LA with the warm front moving inland across all of SE TX. Elevated instability above the retreating cold dome on Monday night into Tuesday morning will support a threat for strong to severe thunderstorms near the warm front or from north of Corpus Christi to Matagorda Bay. Low level wind shear will increase on Tuesday as ESE to SE surface winds veer to SW mid level flow and increase with height producing strong low level wind shear. Thunderstorms that develop along the warm front or in the warm sector will have very favorable low level turning in place for updraft rotation. Low level helicity values increase to 300-500 m^2/s^2 on Tuesday supporting tornado production in supercell type thunderstorms. Only limiting factor may be a lack of good instability with forecasted CAPE values of 400-800 J/Kg. The setup is similar to the 1-9-12 tornado outbreak over SE TX, only this event will be much longer in duration and wind fields slightly stronger.

 

Main severe threat will be damaging winds and tornadoes. Some sort of squall line or MCS feature may eventually develop over the coastal bend into C TX Wed-Wed PM and spread toward the coast ahead of a Pacific cold front/dry line. Area may very well be in for a prolonged (12-24 hour) period of severe weather threat from Tuesday PM to Wed PM.
 
SPC has already outlooked the SW parts of the area for severe weather on Tuesday and much of the area on Wednesday.
 
SPC Severe Weather Outlook for Wednesday: