Texas Winter 2013-2014

[srainhoutx]

A question for all. Has the NAM and GFS improved since 2009? I know it is yes, but by how much and can it be quantified?

The GFS and NAM have been upgraded and currently a newer version of the NAM is in the works. The fine folks at the NCEP are always upgrading the various modeling schemes to improve their output.

[wxman57]

12Z GFS precip amount/type maps are in at WxBell. Shows sleet for Houston early Friday morning with light snow just to our north. Going to have to crank up the global thermostat again. Changed my return flight from New Orleans to 2:40pm form 7:10pm.

[Portastorm]

The indomitable Paul Kocin is working the winter weather desk in DC. Below is his snippet from the early morning discussion:

DAY 3...

...TEXAS...

AS A HUGE AND COLD SURFACE ANTICYCLONE DROPS SOUTHWARD EAST OF THE
ROCKIES...EAST TO SOUTHEASTERLY FLOW WILL BRING MOISTURE INLAND
ACROSS TEXAS AS COLDER AIR MOVES SOUTHWARD ACROSS THE STATE. THE
POSSIBILITY OF LIGHT SNOWFALL OVER CENTRAL TEXAS COULD BE AN
UNUSUAL OCCURRENCE ON DAY 3...WHILE MIXED FROZEN PRECIPITATION
COULD FALL OVER MUCH OF SOUTH CENTRAL AND SOUTHERN TEXAS AS COLDER
AIR CONTINUES TO DRIFT SOUTHWARD INTO THE SOUTHERN PORTIONS OF THE
STATE. HAZARDOUS DRIVING CONDITIONS FOR RESIDENTS UNUSED TO
DEALING WITH SNOW/SLEET AND FREEZING RAIN/DRIZZLE APPEARS THE MOST
LIKELY PROBLEM AT THIS POINT.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT FOR
ALL 3 DAYS.

[northjaxpro]

We will see Portastorm how thiis upcoming tropical season will shake down. Remember, we have not had a major cane since Wilma in 2005. Overall, other than T.S. Fay '08, T.S. Beryl at my locale and T.S.Debby in '12, the peninsula has been extremely fortunate these past nine years. But, of course, I am dreading when the trend will eventually turn at some point.

As for you guys in TX, I mentioned a couple of days ago that I thought the Pacific shortwave energy coming down late week may be stronger than forecast. I always like the NAM models for synoptic features like this one. NAM does a reasonably good job for winter-time synoptic features, especially in the short to medium range (3-5 days). We will have a good idea by Thursday, but I wouldn't be a bit surprised if models trend to some accumulations across the Hill Country of TX and into SE TX. Tomorrow really promises to be a very interesting model watching day for you guys out there.

[Tireman4]

12Z GFS precip amount/type maps are in at WxBell. Shows sleet for Houston early Friday morning with light snow just to our north. Going to have to crank up the global thermostat again. Changed my return flight from New Orleans to 2:40pm form 7:10pm.

Please no. Not the thermostat of fire....Dadgum it....you did that in 2011 and look where it got us...LOL

[South Texas Storms]

How does the 9z SREF look Porta?

[ndale]

I know some of us look at twisterdata for snow depth. I have a question. Even though it says snow depth is some of that shown actually freezing rain and sleet?

[TheProfessor]

I really hope the models are underestimating the short wave.

[South Texas Storms]

As srainhoutx has noted to me, it's interesting to watch the 500mb flow pattern per the GFS through 96 hours. The model takes the shortwave up and over the ridge, brings it down the east side of the ridge/west side of the trough and then buries it underneath and relatively cuts it off offshore of California. If that does indeed happen, it is easy to understand why the GFS is on a drier trend. And it appears to be the same reason WHY the Euro is also relatively dry. But the NAM and short-range ensembles (SREF) do not take that approach and, thus, they appear much "wetter." They do not bury the upper-level energy beneath the West Coast ridge but instead move it through Texas.

Which model will be right? That's the $10,000 question at the moment.

Good observation guys. That does appear to be the key difference in the models right now. Hopefully the NAM and SREF turn out to be right and the GFS and Euro trend in their direction soon!

[Portastorm]

How does the 9z SREF look Porta?

The 9z SREF shows a solid 24 hours of light precip for the AUS/SAT corridor from midday Thursday to midday Friday. The bulk of that precip appears to be a wintry mix (freezing rain/sleet/snow) with a greater emphasis on sleet/snow. The 24-hr precip total for that area is around .50-.75.

[ThunderSleetDreams]

Dear Wxman57,

May your bike be encased in ice on Friday Morning!

With Frigid Love,

Storm2K

[wxman57]

12Z GFS precip amount/type maps are in at WxBell. Shows sleet for Houston early Friday morning with light snow just to our north. Going to have to crank up the global thermostat again. Changed my return flight from New Orleans to 2:40pm form 7:10pm.

Please no. Not the thermostat of fire....Dadgum it....you did that in 2011 and look where it got us...LOL

I admit that I misread the thermostat setting a bit in 2011. New thermostat has larger numbers for my older eyes. Still looking like a light freeze 29-31 for much of Houston Friday/Saturday. North side might see a few snowflakes if current model runs verify. Moisture will still be quite limited, however.

Just a little over 5 weeks until the warmth of March...

[gpsnowman]

How does the 9z SREF look Porta?

The 9z SREF shows a solid 24 hours of light precip for the AUS/SAT corridor from midday Thursday to midday Friday. The bulk of that precip appears to be a wintry mix (freezing rain/sleet/snow) with a greater emphasis on sleet/snow. The 24-hr precip total for that area is around .50-.75.

What does it show for the Metroplex, Porta?

[TheProfessor]

What about for North Texas? Or is the Nam still my best friend?

[wxman57]

12Z GFS has nothing in the way of precip even remotely close to the Metroplex. Way too dry up north. NAM has much more precip across TX than the GFS. An inch or so in the Metroplex Friday and 1-3" on the north side of Houston (Huntsville to Liberty). NAM typically overdoes the precip.

[BigB0882]

I guess this precip shield just won't make it to southeast Louisiana? I hope someone gets a foot of snow out of it even if it can't be me!

[Portastorm]

How does the 9z SREF look Porta?

The 9z SREF shows a solid 24 hours of light precip for the AUS/SAT corridor from midday Thursday to midday Friday. The bulk of that precip appears to be a wintry mix (freezing rain/sleet/snow) with a greater emphasis on sleet/snow. The 24-hr precip total for that area is around .50-.75.

What does it show for the Metroplex, Porta?

Unfortunately minimal precip chances for the DFW area. If precip makes it to the ground, it would be snow. But the atmosphere appears too dry to support much. It appears to generate about .10-.20 amts over a 24-hr period but I don't know how much of that would evaporate due to the progged dry lower levels.

[srainhoutx]

As srainhoutx has noted to me, it's interesting to watch the 500mb flow pattern per the GFS through 96 hours. The model takes the shortwave up and over the ridge, brings it down the east side of the ridge/west side of the trough and then buries it underneath and relatively cuts it off offshore of California. If that does indeed happen, it is easy to understand why the GFS is on a drier trend. And it appears to be the same reason WHY the Euro is also relatively dry. But the NAM and short-range ensembles (SREF) do not take that approach and, thus, they appear much "wetter." They do not bury the upper-level energy beneath the West Coast ridge but instead move it through Texas.

Which model will be right? That's the $10,000 question at the moment.

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1059 AM EST TUE JAN 21 2014

VALID 12Z FRI JAN 24 2014 - 12Z TUE JAN 28 2014

...PATTERN OVERVIEW...GUIDANCE/UNCERTAINTY ASSESSMENT...SENSIBLE
WEATHER HIGHLIGHTS...

A RESILIENT LARGE SCALE FLOW PATTERN OVER NOAM AND VICINITY
REMAINS AS AN ESTABLISHED PACIFIC STORM TRACK LIFTS UP TO ALASKA
ON THE WRN PERIPHERY OF AN AMPLIFIED AND WARMED MID-UPPER LEVEL
MEAN RIDGE CENTERED OVER FAR WRN NOAM. THIS SCENARIO OFFERS ABOVE
NORMAL PREDICTABILITY. THIS PATTERN IS REINFORCED FOR MUCH OF THE
UPCOMING MEDIUM RANGE FORECAST PERIOD THIS WEEKEND INTO EARLY NEXT
WEEK ALLOWING A SERIES OF HARDER TO DIAGNOSE IMPULSES ALOFT AND
SURFACE FRONTS/LOWS AND ASSOCIATED WINTER PCPN SWATHS/SUBSEQUENT
ARCTIC COLD SURGES TO DROP OVER THE RIDGE INTO AN AMPLIFIED
EAST-CENTRAL NOAM MID-UPPER LEVEL MEAN TROUGH POSITION. WHILE THE
TIMING OF THESE COLD SURGES IS LESS UNCERTAIN...THE OVERALL FLOW
PATTERN IS HIGHLY SUPPORTIVE FOR MULTIPLE LOWS/ARCTIC OUTBREAKS
INTO THE CENTRAL AND ERN US INCLUDING THROUGH THE SRN AND SERN
US/FL WHERE TEMPS WILL AVERAGE WELL BELOW NORMAL. THESE ARE
DEPICTED ON WPC MEDIUM RANGE SURFACE FRONTS/PRESSURE AND 500 MB
PROGS. THESE PROGS HAVE BEEN PRIMARILY DERIVED FROM A COMPOSITE
MODEL AND ENSEMBLE SOLUTION USING THE QUITE COMPATABLE 06 UTC
GFS/GEFS ENSEMBLE MEAN AND 00 UTC ECMWF/ECMWF ENSEMBLE MEAN INTO
DAY 4/SAT IN A PERIOD WITH REDUCED FORECAST SPREAD AND CONSISTENT
WITH SHORT RANGE PREFERENCES AS PER THE WPC PMDHMD DISCUSSION.
AMID GROWING EMBEDDED SYSTEM UNCERTAINTY...PREFER USAGE LIMITED TO
A BLEND OF THE 06 UTC GFS ENSEMBLE MEAN/00 UTC ECMWF ENSEMBLE MEAN
FOR THE PERIOD FROM SUN THROUGH NEXT TUE...DAYS 5-7. THIS BLEND
WAS WEIGHTED STRONGER TOWARD THE ECMWF ENSEMBLE MEAN THAT SEEMS TO
BETTER OVERALL MAINTAIN INTEGRITY OF THE OVERALL LARGER SCALE
ANCHORING MEAN RIDGE DURING THIS TIME FRAME THAT SHOULD BETTER
DRIVE DOWNSTREAM FLOW EVOLUTION.

SCHICHTEL

[orangeblood]

What about for North Texas? Or is the Nam still my best friend?

With the 09Z SREF now being much less robust with precip, the NAM and only one GFS ensemble member show precip for North Texas. The downside of a faster/colder solution is the likelihood of a drier solution as well particularly as you go further north.

[orangeblood]

12Z GFS has nothing in the way of precip even remotely close to the Metroplex. Way too dry up north. NAM has much more precip across TX than the GFS. An inch or so in the Metroplex Friday and 1-3" on the north side of Houston (Huntsville to Liberty). NAM typically overdoes the precip.

Except for 2010 Snowmaggedon