Texas Fall 2013

[dhweather]

12Z Euro looks like a 1042MB High dropping down to Kansas, and a freeze for a large part of Texas next Wednesday/Thursday.

From The FWD AFD


A RIDGE IN THE WESTERN STATES WILL BEGIN TO STRONGLY AMPLIFY EARLY
NEXT WEEK. THE RIDGE AXIS WILL EXTEND FROM THE DESERT SOUTHWEST
INTO THE NORTHWEST TERRITORIES...ALLOWING ARCTIC AIR TO SPILL INTO
THE CONUS. SURFACE PRESSURES IN THE CORE OF THE ANTICYCLONE ARE
EXPECTED TO EXCEED 1045MB. THERE ARE STILL INTER-MODEL
DISCREPANCIES IN TERMS OF FRONTAL TIMING...WHICH FOR NORTH AND
CENTRAL TEXAS WILL BE EITHER TUESDAY OR WEDNESDAY. GUIDANCE IS
NOTORIOUSLY SLOW WITH COLD SHALLOW AIR MASSES...THUS INTER-OFFICE
COORDINATION FAVORS THE EARLIER TUESDAY ARRIVAL. WITH LIMITED LOW-
LEVEL MOISTURE AND UPPER FORCING WELL NORTHEAST OF THE REGION...
WILL KEEP A RAIN-FREE FORECAST. A SHORTWAVE MAY GLIDE OVER THE
COOL AIR LATE NEXT WEEK...RESULTING IN THE NEXT CHANCE FOR
PRECIPITATION...BUT THIS IS BEYOND THE CURRENT 7-DAY FORECAST.

[Rgv20]

18zGFS Ensemble Means have a very healthy 1038-1039mb High in the Central Plains by Tuesday Night.



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[Ntxw]

While a cold air mass is poised to come down (thanks to NPAC ridging) I think the bulk will be aimed towards the east and Texas is side glanced, Aleutian ridging doesn't aim for Texas. What is more interesting is what happens after. The ridging in the Aleutians will be replaced by a deep trough thus shifting the ridge to Alaska and into NW North America. This is when we will see the EPO tank and the AO finally go negative and the pipeline to the Arctic opens heading closer to Thanksgiving.

And questions on why there is so much ridging in the NPAC. This has been going on all year. In the spring we had a cold March and April and July saw a freak chill, all connected to anomalous warm temps in the Gulf of Alaska and this is still going on.

[Texas Snowman]

Fort Worth discussion this morning:

"THE ECMWF IS NOW IN BETTER AGREEMENT WITH THE GFS CONCERNING OUR
NEXT COLD FRONT. BOTH NOW AGREE ON TUESDAY AND THAT THE AIRMASS
WILL ORIGINATE FROM NORTHWEST CANADA. TEMPERATURES IN THIS REGION
ARE RUNNING IN THE TEENS AND 20S WITH SURFACE PRESSURES AROUND
1028 MB. THE TRAJECTORY OF THE HIGH PRESSURE CENTER WILL TAKE IT
ACROSS THE NORTHERN PLAINS AND INTO THE MID-SOUTH REGION BY MIDDAY
WEDNESDAY. FOR THIS FORECAST...THE FRONT TIMING WILL BE: CROSSING
THE RED RIVER EARLY TUESDAY MORNING...THROUGH DFW BEFORE MIDDAY
AND THROUGH WACO...KILLEEN AND TEMPLE EARLY AFTERNOON. GUSTY NORTH
WINDS AND MUCH COLDER TEMPERATURES WILL FOLLOW.

WE/VE CONTINUED OUR TREND OF KEEPING TEMPERATURES BEHIND THE COLD
FRONT 5 TO 10 DEGREES BELOW CURRENT MOS GUIDANCE...BUT THIS MAY
NOT BE ENOUGH IF WE TRULY RECEIVE A DIRECT BLOW OF THIS ARCTIC
AIRMASS. FOR NOW SETTLED ON LOWS IN THE UPPER 20S TO MID 30S ON
THURSDAY MORNING AND HIGHS IN THE 50S WEDNESDAY AND THURSDAY.
FRIDAY WILL BE SLIGHTLY WARMER. ALTHOUGH A COUPLE SITES IN THE
NORTHWEST PORTION HAVE REACHING FREEZING THIS SEASON...THIS EVENT
COULD PRODUCE OUR FIRST WIDESPREAD FREEZE. 75"

[Ntxw]

If you have sensitive plants you want to keep I think now is a good time to prepare them for a good, hard freeze next week. Probably only the big urban city centers might escape with a light freeze. Both Euro and GFS gets many down to 30 or below.

[gboudx]

From jeff regarding the cold front, and also a .gif of that Super Typhoon. Wow!

Very active weather period expected over the next several days.

Cool high pressure is shifting eastward with easterly low level winds developing ahead of a quick moving trough in the sub-tropical flow. High clouds will continue to spill into the area today into Saturday with low level moisture gradually returning. A slight chance of light rainfall/showers can be expected late Saturday into Sunday.

Onshore flow continues with gradually warming temperatures through Monday before a very strong cold front crosses the region late Tuesday/Wednesday of next week. Models have backed down some on the intensity of the surface high with this front from around 1045mb yesterday to 1030mb today…but still the potential for some cold arctic air to arrive by the middle of next week. Could see lows well into the 30’s and highs only in the 50’s Wednesday and Thursday.

Potential for a major storm system to affect the area toward the weekend of the 16th at the moment. Both GFS and ECMWF are in decent agreement on a fairly deep storm system moving across TX during this time period, but this is still over a week away and a lot will change between now and then.

Super Typhoon Haiyan:

Yesterday evening (local time) the strongest tropical cyclone to ever make landfall in the world struck the Philippines Islands with sustained surface winds of 195mph. The city of Tacloban suffered a direct impact from the eyewall and a the few reports from the city indicate extreme damage from both wind and storm surge as one would expect from the intensity of a tropical cyclone hit.

[ravyrn]

It has now been 35 days since I last turned on my A/C

[Ntxw]

This idea I had using indices that the start of November would start mild is just not going to happen. I was discussing with Portastorm how the chilly weather is occuring at the face of an AO that is very, very positive. Clouds and damp conditions have persisted and DFW, Austin, and Houston are all some 2-3c below normal. With a freeze coming to most of the state and hard freeze away from urban areas is going to sink the departures even more. Another chilly air mass may follow, while both are likely to be transient they just reinforce what has been.

In other news, anomalous ridging continues over the NPAC

[Portastorm]

There's a fairly wide disagreement between King Euro and the GFS for the next 8-10 days for the Southern Plains and Texas. If the Euro were to verify, we're looking at an anomalously cold period with several low latitude storm systems.

Here's the 0z Euro over the next 10 days:

http://www.meteo.psu.edu/~fxg1/ECMWF0.5_0z/ecmwfloop.html

[vbhoutex]

There's a fairly wide disagreement between King Euro and the GFS for the next 8-10 days for the Southern Plains and Texas. If the Euro were to verify, we're looking at an anomalously cold period with several low latitude storm systems.

Here's the 0z Euro over the next 10 days:

http://www.meteo.psu.edu/~fxg1/ECMWF0.5_0z/ecmwfloop.html

I'll be interested to see how these models progress, especially since we will be in the Solado area next weekend.

[Ntxw]

Freeze is coming to most north of I-10 and hard freeze for the I-20 corridor. Freeze warnings will probably come out today or tomorrow. If you are in the counties surrounding Dallas and Tarrant you will probably get down into the mid-20s. Pets and plants people!

[dhweather]

The 12Z Euro looks like another I-10 freeze early/mid next week.

[Ntxw]

The 12Z Euro looks like another I-10 freeze early/mid next week.

Possible that one will pack a bit more punch and last a little longer. Freeze part deux, +PNA and lowering AO to boot.



Tricky these shallow arctic air masses. I did some skewT's for the cold air next few days and it's actually pretty mild above. 850mb and higher never really is below freezing yet we manage sub 30 temperatures. The same case even in states further north.

[TeamPlayersBlue]

What are skewT's? I understand what you mean by shallow air mass but what are skewT's?

It seems pretty dense with such a high value (1044MB) coming down. Is there anything that makes them more shallow then others? Thanks for the info.

[wxman57]

On the bright side, back to the 80s in Houston this weekend!

[ravyrn]

Looks like a few areas in extreme NETX may come pretty close to record low temps tonight. Texarkana is forecast to get down to 26, and I believe 24 is their record set in 1911.

[vbhoutex]

Depending on who you listen to we are supposed to be around 34f-36f for lows in the morning, which is quite a bit below normal for us. I am wondering if we will make it though since we currently have heavy cloud cover. That will have to go away if we are going to go that low.

[TeamPlayersBlue]

Im an idiot, i know what a SkewT is lol

[Ntxw]

What are skewT's? I understand what you mean by shallow air mass but what are skewT's?

It seems pretty dense with such a high value (1044MB) coming down. Is there anything that makes them more shallow then others? Thanks for the info.

Skew-T is basically just a plot of the soundings, or temperature profile in the entire column above our heads.

Example of Dallas' tomorrow morning. Notice the below freezing temps is just below 850mb which is basically near the surface. At 850 to 700mb which is approx 5k to 10k feet the air is above freezing, in front of the 0c line. This means the cold air is shallow, if precip were falling in this air mass it would be freezing rain most likely. It's a good way to determine what kind of precip may fall in winter. If it was a deep cold air mass it would be freezing just about throughout the entire column.



How dense an air mass is I can't say for sure, but it's usually source region that determines. Arctic air masses tend to be more shallow than Canadian air masses.

[TeamPlayersBlue]

Thanks for the explanation, yeah i recognized that as very shallow. Thats crazy but the air is pretty dense. I looked at some SkewT's for cities in the northern plains and the air is sinking all the way up to the 200 MB level. Crazy.