Texas Winter 2014-2015

[srainhoutx]

Lord have MERCY!!! Too many acronyms for this novice to comprehend! Can you please explain all this in English, and feel free to talk to me like I'm stupid. I won't be offended!

This is what I wrote this morning, forecast wise and goes along the lines of exactly what wxman57 was probably posting here on S2k at the same time.

A rather expansive upper trough that extends from NE Canada SW to near the Baja of NW Mexico looks to remain as pool of very chilly air is pushing S across the Canadian Prairies. The various computer models continue to struggle with the fast flow and how the next upper disturbance evolves that is currently taking shape near British Columbia. The guidance is in general agreement that this upper air disturbance will drop S through the Great Basin toward Southern California/Arizona on Monday. As the storm system plunges S, a powerful Arctic airmass with its 1055mb+ Artic High will spread quickly S into Colorado/Wyoming and into the Central Plains. This very cold dense shallow air mass is expected to race S into Texas on Tuesday with the Arctic front modifying as it drops S across Texas. The fly in the ointment continues to be what happens to our West and just how fast or slow the upper low/disturbance ejects E. The various computer models have been slow to move the upper low/trough once it settles into NW Mexico/Southern Arizona and suggest it may even cut off from the main Northern stream flow. It is a typical computer model error to cut off upper air disturbances with a relative fast flow pattern in the medium range. It is also a know computer model error to under estimate very dense, cold and shallow Arctic airmasses. The Operational Global models as well as the short range meso guidance are in excellent agreement that a very strong 1055 t0 1060mb+ Arctic High is coming South. That much agreement bodes well that a strong push of very cold air is coming. The other details are still 4 to 5 days out regarding what happens to our West with the upper trough and any embedded disturbances riding over the cold, dense and shallow cold air at the surface. In fact we may not have a real solution to our sensible weather before 24 to 36 hours out as the guidance struggles with this very complicated pattern as we end December 2014 and ring in the New Year of 2015.

[Rgv20]

12zGFS-Parallel is a lot colder than the 12zGFS Operational run for Austin, San Antonio, and the Upper Rio Grande Valley. Temperature to stay around the freezing mark all day (Wednesday 31st) in the Austin and San Antonio area and for my area it has temperature in the mid to upper 30s.

[aggiecutter]

After looking at 12z GFS, I've come to the conclusion(based on past experience) that the models are eroding the dense cold air too quickly next week. When the moisture returns late next week, there still should be a shallow layer of cold air at the surface, particularly east of I-35. Unfortunately, this looks like a classic freezing rain setup for portions of East and NE Texas.









This forecast is just my opinion based on past experience, as I am not a Pro-Met, or slept in a Holiday Inn Express the night before like Portastorm.

[Tammie]

Thank you very much! That I can understand!!!

[Ntxw]

Im seeing signs ridging may sit in Alaska. This likely means another arctic attack could be on the heels of the first one. The events that occur may resemble the transition that happened in 1983 at 500mb but not quite as intense. Im not calling for something like that but just the flow is eye popping.

[ThunderSleetDreams]

The local station in Longview is forecasting 27 to 34 on Wednesday and Thursday with 30% chance of precip. That is colder than the models. I think most common sense mets are slanting that way.

[orangeblood]

Im seeing signs ridging may sit in Alaska. This likely means another arctic attack could be on the heels of the first one. The events that occur may resemble the transition that happened in 1983 at 500mb but not quite as intense. Im not calling for something like that but just the flow is eye popping.

This, with that kind of flow out of the Arctic Circle, the low level dense cold should overwhelm the pattern...forcing storms much further south and east than models are showing attm. GFS P is picking up on this, it builds HP back in the plains quickly after the 1st one next week moves eastward/forcing the ejecting ULL out of the southwest much further south across south Texas. Would be shocked if that ULL cut to the lakes like some models are currently showing

[Ntxw]

Especially the GFS, for a progressive model the things its doing raises an eyebrow. With a SE ridge forming, the flow is directly discharging down the Great Plains into Texas. Watch the source region the next several days, it could give us a hint if this is a run of the mill arctic blast or something more. Canada is getting very cold. You can't have a 1055+ hp as consensus and show wimpy surface cold, either the hp is overdone or the cold air is underdone.

[ronyan]

I'd be willing to bet they are under doing the intensity of the cold air. The models have been very persistent over the past few days in a 1050+mb high coming into the US, and if anything they are tending stronger with it.

The 12z NAM @ 84 hrs has a 1055mb high entering Montana. GFS and the PGFS are even stronger with the high on Tuesday, 1059mb and 1060mb respectively.

[srainhoutx]

Afternoon briefing from Jeff:

Next storm system heading for TX over the next 36 hours.

Arctic cold front likely middle of next week.

Moisture advection is underway across SE TX this morning with light rain and drizzle covering much of the area. Marine front offshore is attempting to lift toward the coast and may push slightly inland this evening. Cold front extends from KS to WC TX and will slowly move eastward over the next 24 hours helping to bring SE TX a round of showers and thunderstorms. Expect light rain and drizzle to continue much of the day and into the overnight hours. Lift increases ahead of the cold front on Saturday helping to promote heavier showers and thunderstorms. Warm sector air mass may attempt to push inland early Saturday, but this remains only slightly likely with the best potential for any warm sector strong to severe convection being right near the coast and offshore. Most of the area will see mainly showers and a few thunderstorms. Front should reach the coast by early evening with some potential for post frontal rains to continue into Sunday as upper level flow remains out of the SW pushing moisture over the top of the surface cold dome. Sunday will be cloudy with periods of rain and temperatures likely remaining in the 40’s with N winds.

Next Week (Arctic Intrusion):
Monday will likely be the best day of the next week as clouds clear allowing some sun and a modest warm up into the lower 60’s from a cold and cloudy Sunday. However this will be short lived as significant upper air jet stream amplification pumps strong ridging deep into Alaska dislodging a large arctic high pressure cell out of NW Canada. Various global model solutions are all in agreement with the upper air pattern which is favorable for arctic air masses to move southward into TX. Agreement is also that the arctic surface high pressure cell will be on the order of a 1050-1060mb pressure at the surface and enter the US through Montana early next week. Simply stated that is a mighty strong arctic high pressure cell that will dam against the Rocky Mountains and funnel its cold air southward rapidly down the front range.

The problems lie within the model guidance output of temperature forecast post arctic front next week. It is well known that global models handle shallow dense arctic air masses poorly especially those that dam against the front range of the Rocky Mountains. Models tend to be too slow and too weak with the air mass especially in this time frame and once the dense cold air is on the move try and grasp what is happening and have significant temperature decreases in the 72-48 hour time period. Forecasters and media output of raw model guidance are significantly too warm for the Wednesday-Friday period of next week given the gravity of the high pressure being forecast, which is actually in good model agreement. For example the GFS model is forecasting a high of 49 next Thursday (1/1) for IAH. I would easily undercut this by 10 degrees and maybe more. Experience tells us that these shallow dense arctic air masses will arrive faster and colder than model guidance. With that said, will show the arctic front through the area and off the coast by Tuesday evening with strong cold air advection following. Will undercut guidance by at least 5 degrees and that is likely not enough from Wednesday through Friday with lows in the 30’s (possibly upper 20’s) and highs in the upper 30’s to low 40’s. Again these numbers may need to be lowered more in the coming days and highs on New Year’s Day may struggle to reach the mid 30’s.

Arctic fronts are notorious for being shallow in nature (usually only a few thousand feet deep) which typically makes for a very cold surface layer which is then overrun by warm air in the mid levels. This creates an overrunning situation not all that different from today or what is expected on Sunday, but with significantly colder surface temperatures. This pattern tends to support lots of thick clouds and at times precipitation in the arctic air mass. Additionally, it can help keep the cold air locked in place longer and slow air mass modification. Global forecast models are struggling with how to handle the base of the longwave trough which digs deep into the SW US toward the middle and end of next week. A few days ago models were ejecting this system into the arctic air mass over TX on New Year’s Eve and New Year’s Day, but they now delay that until the 2nd and 3rd of Jan. giving the shallow arctic air mass a bit of time to moderate. This appears to cut back on the potential for a winter storm across TX on New Year’s Eve and Day at the moment if the models are correct on the timing of this upper air system…delaying it. There is a lot of uncertainty in this part of the forecast (31st -3rd) with respect to the modification of the arctic cold dome and when any upper level system will cross the state. The pattern thus far has been very progressive, so I am not sure the slowing and cutting off of the upper system over the SW US is in fact correct. Likely something in the middle will be what actually transpires and then the question becomes how much if any has the downstream arctic air mass over TX warmed.

[TeamPlayersBlue]

Are there any good analogs but I can look at when I get home try compare this event to? I will have a few hours to entertain myself later on

[TeamPlayersBlue]

It looks like the Nam at 84 hours has the center of the upper level low farther east than any other model. I think as far as timing goes we want the upper level low to be a little bit further east than what the models have been projecting.

[Rgv20]

12zECMWF has a 1055mb High in Montana by Mid-day Tuesday, but in my opinion it looks way too warm with surface temperatures and slow with the Arctic Front for Texas. I'm betting the 12zECMWF Ensembles are going to be colder than the operational run.

[ronyan]

12zECMWF has a 1055mb High in Montana by Mid-day Tuesday, but in my opinion it looks way too warm with surface temperatures and slow with the Arctic Front for Texas. I'm betting the 12zECMWF Ensembles are going to be colder than the operational run.

Yeah the 12z Euro actually has 850mb temps above normal for coastal TX on the 1st, doesn't seem likely at all.

[Rgv20]

12zGFS Ensemble Means forecast a 1058mb High and the 12zECMWF Ensemble Means forecast a 1052mb High in Montana by Tuesday Morning.

[wxman57]

12zECMWF has a 1055mb High in Montana by Mid-day Tuesday, but in my opinion it looks way too warm with surface temperatures and slow with the Arctic Front for Texas. I'm betting the 12zECMWF Ensembles are going to be colder than the operational run.

Yeah the 12z Euro actually has 850mb temps above normal for coastal TX on the 1st, doesn't seem likely at all.

And not even close to a freeze in Dallas for the next 10 days. Models are truly lost...

[Rgv20]

12zECMWF has a 1055mb High in Montana by Mid-day Tuesday, but in my opinion it looks way too warm with surface temperatures and slow with the Arctic Front for Texas. I'm betting the 12zECMWF Ensembles are going to be colder than the operational run.

Yeah the 12z Euro actually has 850mb temps above normal for coastal TX on the 1st, doesn't seem likely at all.

And not even close to a freeze in Dallas for the next 10 days. Models are truly lost...

Or maybe for the first time in weather history an Arctic Front will stop midway in Texas and retreat back north as a warm front.......

[wxman57]

Or maybe for the first time in weather history an Arctic Front will stop midway in Texas and retreat back north as a warm front.......

Nah...

[TeamPlayersBlue]

12zECMWF has a 1055mb High in Montana by Mid-day Tuesday, but in my opinion it looks way too warm with surface temperatures and slow with the Arctic Front for Texas. I'm betting the 12zECMWF Ensembles are going to be colder than the operational run.

Yeah the 12z Euro actually has 850mb temps above normal for coastal TX on the 1st, doesn't seem likely at all.

It has 850 MB winds coming out of the south. That is the reason for why it is indicating warmth. #Wrongo

[Ralph's Weather]

The Euro is clueless. The GFS is sorta on track. And the PGFS is actually decent though still not cold enough or fast enough. I think I heard the the NAM is looking decent but we are still abut out of its range. Everybody relying on their weather apps are going to be in for a shock.