December: New Years Eve Outlook

[Andrew]

HGX AFD:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
440 AM CST THU DEC 19 2013

.DISCUSSION...
LOW LIGHT SATELLITE SHOWING MOSTLY CLOUDY SKIES ACROSS SOUTHEAST
TEXAS THIS MORNING. RADAR IS ALSO STARTING TO PICK UP VERY LIGHT
RETURNS OVER THE COASTAL WATERS TO THE SOUTHWEST. NAM 12 SHOWING
SOME LIGHT PVA CURRENTLY MOVING OVER THE SOUTHWESTERN AREAS. KCRP
SOUNDING ALSO SHOWS A PRETTY THICK SATURATED LAYER. THE PVA WEDGE
WILL CONTINUE TO PUSH TOWARDS THE NORTHEAST DURING THE DAY TODAY
AND IN COMBINATION WITH THE WAA THINK LIGHT STREAMER SHOWERS AND
DRIZZLE WILL BE POSSIBLE. HIGH RES HRRR AND TEXAS TECH WRF ALSO
SUPPORT THIS. THIS TREND OF LIGHT SHOWERS UNDERNEATH THE CAP WILL
PERSIST TODAY AND FRIDAY AHEAD OF THE NEXT UPPER LEVEL SYSTEM.

AS HAS BEEN ADVERTISED THE LAST COUPLE OF DAYS A SHORTWAVE IS
CURRENTLY DIVING SOUTHWARDS FROM THE PACIFIC NORTHWEST. THIS
ENERGY WILL EVENTUALLY WRAP UP INTO AN UPPER LEVEL LOW OVER THE
BAJA OF CALIFORNIA. THE UPPER LEVEL LOW WILL THEN TRACK EASTWARDS
AND EJECT OFF TOWARDS THE NORTHEAST OVER THE TEXAS PANHANDLE.
MODELS ARE STILL SHOWING THE LOW TO GAIN A NEGATIVE TILT TO IT.
UPPER LEVEL DYNAMICS APPEAR TO BE MORE FAVORABLE AGAIN FOR
SATURDAY AS THE ECMWF... GFS... CANADIAN... AND NAM 12 ALL PUT
SOUTHEAST TEXAS IN THE RRQ. SHEAR VALUES REMAIN IMPRESSIVE. 30 KTS
OR GREATER OF SFC TO 1KM SHEAR (SRH ~220 M2/S2) CAN BE FOUND IN
MOST FORECAST SOUNDINGS WITH MODEST CAPE VALUES. WHAT REMAINS TO
BE IN QUESTION IS HOW MUCH DRY AIR AND CAPPING SOUTHEAST TEXAS
WILL HAVE. ECMWF FORECAST SOUNDINGS ARE BY FAR THE MOST MOIST WITH
PWATS APPROACHING 2.00" IN THE IAH FORECAST SOUNDING SATURDAY
EVENING. THE NAM 12 AND GFS ARE SIMILAR WITH MOISTURE VALUES
AROUND 1.60". BOTH THE GFS AND NAM FORECAST SOUNDINGS DO HAVE A
DRY LAYER AROUND THE 700 MB AREA. AS OF NOW THE AMOUNT OF DRY AIR
DOES NOT APPEAR TO BE TO GREAT FOR STORM FORMATION. FORECAST
SOUNDINGS ALSO ERODE THE CAP SATURDAY AFTERNOON. THIS WOULD IN
GENERAL MAKE SENSE GIVEN THE MID- LEVEL COOLING EXPECTED WITH THE
UPPER LEVEL LOW. WITH THE 850 MB SOUTHWESTERLY FLOW THOUGH THIS
MIGHT BE TOUGH. MODEL QPF FIELDS HAVE ALSO BEEN HINTING AT A
SECONDARY QPF BULLS EYE OUT AHEAD OF A MAIN LINE. THIS IS MOST
LIKELY FROM DISCRETE CELLS IN ASSOCIATION WITH THE WARM CONVEYOR
BELT. GIVEN THE ABOVE STRONG TO SEVERE STORMS CERTAINLY SEEMS
POSSIBLE. THE DISCRETE CELLS OUT AHEAD OF THE MAIN LINE COULD HAVE
SOME ISOLATED TORNADOES WITH WIND DAMAGE. THE MAIN LINE IS
CURRENTLY PROGGED TO MOVE THROUGH LATE SATURDAY EVENING. THE LINE
MIGHT HAVE TROUBLE HOLDING TOGETHER IN THE SOUTHWEST WHERE THE CAP
WILL BE STRONGER BUT WILL WAIT FOR FUTURE MODEL RUNS TO HELP
NARROW THESE FINE DETAILS DOWN. STRONG TO DAMAGING WINDS WITH
EMBEDDED TORNADOES WILL BE POSSIBLE IF STORMS DO END UP GOING
LINEAR. DUE TO THE MENTIONED ABOVE SPC HAS NOW INCLUDED SOUTHEAST
TEXAS IN SLIGHT RISK FOR DAY 3.

[srainhoutx]

The 30% area outlined within the Slight Risk issued by the SPC Day 3 Outlook include College Station, Lufkin, Lake Livingston Texarkana, Temple Shreveport, Louisiana and El Dorado, Arkansas. Currently all other areas including Metro Houston/Austin, Beaumont/Lake Charles/New Orleans are in a 15% area. There are indication that an MCS or Meoscale Convective System may develop late Saturday evening across portions of SE/E Texas extending into Louisiana. This is a sort of rare event to see the SPC outline a Slight Risk in the late December time frame at the Day 3 range, so it warrants monitoring. A variety of Winter Weather Advisories/Watches are being hoisted from Southern California in the higher elevations extending as far S as the San Diego area (where thundersnow may be possible due to the dynamic nature of this potent cold core upper low) on E with Flash Flood Watches across potions of Arkansas, Misourri and points E and Winter Weather in the form of freezing rain and sleet (with some locations possibly heavy) and some snow extending into the Chicago Area and the Great Lakes Region for those with weekend travel plans.

[unome]

http://www.spc.noaa.gov/products/outlook/day3otlk.html

[unome]

TWC's take on it: http://www.weather.com/video/severe-wea ... kend-41272

Torcon 5/4

[Andrew]

Looking at the overnight runs, the models showed more "promise" for severe weather on Saturday. It looks like starting tomorrow we should see a nice increase in moisture levels as an increasingly strong flow from the gulf takes over. PW's look to max out Friday at 1.3 to 1.4in which should be enough to see some streamer showers progress through the area. We then need to look out west where heights will begin to fall as a mid level trough dips into the state. Overnight the models have progressed slower with the trough but continue to advertise a shortwave rotating around. The slower movement should allow for a more neutral/negative tilt of the shortwave when it progresses through the state increasing severe chances. There will be a nice southerly flow at the surface and a SW flow through the rest of the column allowing for plenty of shear. A LLJ will approach the area early Saturday with 50-60kt winds extending right above the surface creating 30-40kts of shear. CAPE values should range between 1000-1500J/Kg depending on timing of the system. If we can maximize daytime heating then the Cap will only help to increase the probability of discrete cells versus a strictly linear system. Looking at some of the soundings for the area, the GFS has a 1000J/Kg of CAPE present with an EHI of 2.4 at 6am on Saturday. That is pretty impressive for December especially at 6am. A lot of things to watch in the coming days.

[Andrew]

We need the morning Dr. Jeff e-mail stat.

no email yet....

[snowman65]

I would like to see a fresh meteogram from WXMAN57 for next week ..please..

[srainhoutx]

Taking a look at a bigger picture regarding the impacts of this Winter Storm since many will be traveling over the weekend prior to Christmas, the impacts from a travel and societal point of view appear rather large. In the higher elevations of Southern California into Northern Mexico, heavy snow as well as thunder snow are possible later today into tonight extending S into the mountains just W of San Diego. As the cold core upper low wraps up and develops, snow will spread further E into Arizona and New Mexico and even Northern Mexico across higher elevations. There is a significant tap of rich sub tropical moisture associated with this storm system. As the upper low begins to head E across Northern Mexico, the stalled Polar boundary should stall across the Big Country of West Texas and just S of the Dallas/Ft Worth Metroplex setting the stage for an icy mess across the Southern/Central Plains including Oklahoma and Kansas and further N and E into the Upper Mid West (Chicago/St Louis/Kansas City areas) as well as the Great Lakes Region and Southern New England. In the warm sector across the Mid Mississippi/Ohio/Tennessee Valley Region, Flash flood issues are also possible extending further NE.

[unome]

watching the dry air slot getting squeezed, better seen in the loop, here:

http://www.atmos.washington.edu/~ovens/ ... nced+/48h/

[srainhoutx]

It's not even winter yet, folks. 12Z Euro has a 1058mb high dropping into the Northern Plains by the 27th with temps there 45-50 degrees below normal. We'll see if that materializes and how we might be impacted in another 5-7 days.

LOL... look what the GFS just delivered for the New Year...

[MontgomeryCoWx]

Not that I believe anything from the GFS or Euro these days past 192 hours, but that is a hellacious and anomalous arctic breakout.

It looks like the NEPAC ridge swallows Siberia and the pole locking in cold over here. Ahhh, I hope it pans out, but I'm not holding my breath.

[srainhoutx]

Not that I believe anything from the GFS or Euro these days past 192 hours, but that is a hellacious and anomalous arctic breakout.

It looks like the NEPAC ridge swallows Siberia and the pole locking in cold over here. Ahhh, I hope it pans out, but I'm not holding my breath.

Well to be fair, the various global deterministic and ensembles are sniffing the EPO going negative around Christmas. Those warm sea surface temperatures across the N Pacific and Gulf of Alaska are not going to suddenly go cold. That does tend to favor a lot of volatility via the guidance, but we will leave that until next week...if the trends continue.

[MontgomeryCoWx]

In lay terms... "they'll eventually get it right if we continue to get a largely negative EPO."

Do you think the PNA and AO will help us out and go positive and negative, respectively.

[srainhoutx]

In lay terms... "they'll eventually get it right if we continue to get a largely negative EPO."

Do you think the PNA and AO will help us out and go positive and negative, respectively.

The PNA is trending positive next week. The AO as of today for the longer range is clueless.

[srainhoutx]

Back to the real time weather worries...

12192013 1121 AM Day 2 SPC day2otlk_1730.gif

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1121 AM CST THU DEC 19 2013

VALID 201200Z - 211200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
A PROGRESSIVE/SPLIT LARGE SCALE PATTERN WILL EXIST OVER THE CONUS ON
FRIDAY...HIGHLIGHTED BY EXTENSIVE CYCLONIC UPPER FLOW OVER MUCH OF
THE CONUS AND THE GENERAL EASTWARD ADVANCEMENT OF A POTENT UPPER
TROUGH/POLAR JET OVER NORTHWEST MEXICO. AIR MASS MODIFICATION WILL
STEADILY OCCUR ESPECIALLY OVER THE SOUTH-CENTRAL CONUS...WITH AN
INCREASING MOIST BOUNDARY LAYER BECOMING ESTABLISHED ALONG/SOUTH OF
A FRONTAL ZONE FROM PARTS OF TX/ARKLATEX NORTHEASTWARD INTO THE
LOWER OH RIVER VALLEY.

...PORTIONS OF TX/ARKLATEX...
AS SOUTHERN HIGH PLAINS CYCLOGENESIS GRADUALLY OCCURS FRIDAY...THE
PRIMARY SURFACE BOUNDARY WILL STALL/ORIENT SOUTHWEST-NORTHEASTWARD
FROM SOUTHWEST TX TO THE OH VALLEY...WITH A FRONTAL WAVE/SURFACE LOW
MOVING EASTWARD ACROSS THE MIDWEST/OH VALLEY. WITHIN THE NEARBY WARM
SECTOR...LOWER TO MIDDLE 60S F SURFACE DEWPOINTS WILL BECOME
INCREASING PREVALENT ACROSS THE SOUTHERN HALF OF TX AND ADJACENT
ARKLATEX/LOWER MS RIVER VALLEY.

IN SPITE OF INCREASING BOUNDARY LAYER MOISTURE...THE MAJORITY OF THE
REGION WILL BE INFLUENCED BY WEAK OVERALL FORCING AND SUBTLE HEIGHT
TENDENCIES /IF NOT WEAK HEIGHT RISES/...AT LEAST THROUGH THE
DAYLIGHT HOURS. THIS SCENARIO...WITH AN INCREASINGLY STOUT ELEVATED
MIXED LAYER ACROSS TX...SHOULD GENERALLY CAP THE WARM SECTOR WITH
THE POSSIBLE EXCEPTION OF FRIDAY NIGHT IMMEDIATELY NEAR THE FRONT.

AS GRADUAL HEIGHT FALLS BEGIN TO INFLUENCE TX FRIDAY NIGHT VIA THE
NORTHWEST MEXICO/SOUTHWEST STATES UPPER TROUGH...A STRENGTHENING LOW
LEVEL JET/ASSOCIATED ISENTROPIC UPLIFT FOCUSED NEAR/NORTH OF THE
REGIONAL SURFACE FRONTAL ZONE WILL RESULT IN A NOCTURNAL INCREASE OF
TSTMS. THIS INCLUDES A CORRIDOR FROM SOUTHWEST/CENTRAL TX
NORTHEASTWARD TO THE ARKLATEX/OZARKS. A COUPLE OF NEAR SURFACE-BASED
STORMS CANNOT BE ENTIRELY DISCOUNTED NEAR THE FRONT...BUT THE MOST
PROBABLE/DOMINANT SCENARIO WILL BE FOR STORMS TO DEVELOP/INCREASE ON
THE IMMEDIATE COOL SIDE OF THE SURFACE FRONT...WITH STORMS GENERALLY
ROOTED ABOVE A RELATIVELY COOL/STABLE BOUNDARY LAYER. STRONG SHEAR
THROUGH THE CLOUD LAYER/SUFFICIENT ELEVATED INSTABILITY SUGGEST THAT
MARGINALLY SEVERE HAIL MAY OCCUR WITH A FEW OF THE STORMS. IN SPITE
OF INCREASING DEEP LAYER SHEAR/LENGTHENING LOW-LEVEL
HODOGRAPHS...ANY SEVERE WIND GUST AND/OR BRIEF TORNADO POTENTIAL
WILL BE CONTINGENT UPON NEAR SURFACE-BASED DEVELOPMENT WITHIN THE
WARM SECTOR FRIDAY NIGHT...WHICH APPEARS RELATIVELY LOW/UNCERTAIN AT
THIS TIME.

..GUYER.. 12/19/2013

[wxman57]

Here's a meteogram based on the 12Z GFS. For north Houston (IAH) it has a low near 40 on Christmas Day and a high in the mid to upper 50s. Note the precip indicated starting between 3PM and 6PM. GFS indicates warm air advection beginning early in the morning, bringing increasing clouds and moisture off the Gulf during the day.

[srainhoutx]

The 12Z deterministic Global models are trending to a positive PNA/negative EPO regime in the days following Christmas. We will see if those trends continue and if there is yet another upper low developing to our West next week with a noisy sub tropical jet.

[MontgomeryCoWx]

The 12Z deterministic Global models are trending to a positive PNA/negative EPO regime in the days following Christmas. We will see if those trends continue and if there is yet another upper low developing to our West next week with a noisy sub tropical jet.

YESSSSSSSSSSSSSSS.... Fires up the Canadian Cold Machine.

[srainhoutx]

While it is still a bit too far out to know exactly how the severe event for Saturday actually develop, there are some rather high parameters via the SPC 15Z SREF that will be worth monitoring.

[srainhoutx]

Worse than Wilma? Oh Paul...sigh. Let's not go overboard. I lived through Hurricane Wilma while living in the Florida Keys in 2005. This will not be anything like the widespread damage that left well over a million folks with damage in S Florida. Let's not hype. Thanks.