December 2014: New Year's Eve Wintry Mix Possible

[ronyan]

Any chance of extensive power outages, rotating blackouts, and other energy maladies with this weather system? I couldn't help but notice Jeff mentioning freezing temperatures for daytime highs. I don't think anybody could survive this without working heaters, folks.

Why are you so obsessed with power outages? You can definitely survive sub-freezing temps without a heater. I've camped for days in such weather in the mountains in W TX.

[Paul Robison]

History lesson:



January 1962: The period between 1951 and 1962 brought little cold to the Valley, then in 1962, another long severe freeze again hit the Valley. As in 1951, most of the Valley had over two full days and nights below freezing. Unlike 1951, the skies cleared off toward the end of the freeze and temperatures went lower. This time, the lows went to 19°F in Brownsville, and a brutal 10°F in Rio Grande City, if only briefly. McAllen recorded the lowest ever 17°, one degree colder than 1989. While most subtropicals were again killed to the ground, the citrus industry was not hurt as badly this time since trees were in a more dormant condition. Again, the maximum and minimum are given for Brownsville:




1/9/89 1/10/89 1/11/89 1/12/89
76°/29° 30°/24° 31°/25° 51°/19°



The low of 19° is perhaps not as bad as it sounds. Temperatures on the coldest night went from 30° at 1:00 a.m. to 19° very briefly at 5:30. It was below 26° for 6 consecutive hours and below 23° for 5 hours, which is rather puny when compared to the freezes of the late 1800's or 1980's. The following winter of 1962-63 was also fairly severe, when temperatures when to 24° at Brownsville, with lower twenties further west and even 23° at Port Isabel. That winter was shared in Florida as well.


This a viable scenario?

[srainhoutx]

Merry Christmas Everyone! May this day bring peace and tranquil weather from my home to yours. We have our first heavy frost of the year this Christmas morning in NW Harris County.

[Katdaddy]

Merry Christmas everyone! Well stated Srainhoutx. Peace and happiness to everyone.

[unome]

Happy Holidays Y'all !

keeping fingers crossed for no wintry stuff on the 31st at least - our kiddo has their driving test that morning

http://www.mdl.nws.noaa.gov/~wxgrid/gmos_ndfd.php

warm thoughts, warm thoughts, warm thoughts...

[TexasBreeze]

The models are saying since yesterday "not even close" to frozen precip for Houston.

[srainhoutx]

The models are saying since yesterday "not even close" to frozen precip for Houston.

Let's look at things this weekend into early next week before declaring the New Year Winter storm dead. The ensembles are still suggesting a pattern that is cold for our Region, but full of uncertainty with how much energy is left out to our West. As Jeff and others have carefully mentioned over and over, this does not look like 'historic cold' that some seem to want to believe. That said some across our Region may well have p-type issues as the warm SW flow aloft over runs the shallow cold air at the surface. Typically 1055+mb Arctic High pressure building from Colorado down toward the Texas Panhandle does not just magically stop the dense cold air along the Red River. As we know and wxman57 has repeatedly taught us over the years, the guidance under estimates the magnitude of dense shallow Arctic airmasses. If and it is a big if we see something somewhat similar to what happened in mid November when we experienced 35F and moderate rain and temperatures are just 3-5 degrees 'colder' than expected, all sort of weather related issues could be a big headache in the form of freezing rain. Meanwhile, enjoy the day and the rainy weekend ahead as the next storm system approaches and begins the process of changing are sensible weather pattern.

12252014 12Z NAM nam_namer_060_500_vort_ht.gif

12252014 06Z GFS gfs_namer_129_10m_wnd_precip.gif

12252014 00Z Euro Mean 168 ecmwf-ens_z500a_namer_8.png

12252014 00Z GEFS 168 gfs-ens_z500a_namer_29.png

12252014 00Z GEM 168 gem-ens_z500a_namer_29.png

[Ptarmigan]

Merry Christmas to everyone here.

[cperk]

srainhoutx Merry Christmas and thanks for taking the time write an analysis on our potential winter weather around New Years.You always manage to keep things in perspective.

[cperk]

Oh and MERRY CHRISTMAS to all of our forum members.

[TexasBreeze]

The models are saying since yesterday "not even close" to frozen precip for Houston.

Let's look at things this weekend into early next week before declaring the New Year Winter storm dead. The ensembles are still suggesting a pattern that is cold for our Region, but full of uncertainty with how much energy is left out to our West. As Jeff and others have carefully mentioned over and over, this does not look like 'historic cold' that some seem to want to believe. That said some across our Region may well have p-type issues as the warm SW flow aloft over runs the shallow cold air at the surface. Typically 1055+mb Arctic High pressure building from Colorado down toward the Texas Panhandle does not just magically stop the dense cold air along the Red River. As we know and wxman57 has repeatedly taught us over the years, the guidance under estimates the magnitude of dense shallow Arctic airmasses. If and it is a big if we see something somewhat similar to what happened in mid November when we experienced 35F and moderate rain and temperatures are just 3-5 degrees 'colder' than expected, all sort of weather related issues could be a big headache in the form of freezing rain. Meanwhile, enjoy the day and the rainy weekend ahead as the next storm system approaches and begins the process of changing are sensible weather pattern.

Oh I know I was just mentioning the models face value. 1050 highs don't produce weak or moderate fronts!:)

[BlueJay]

Merry Christmas everyone! I hope all are enjoying this fine weather today.

[ticka1]

awesome christmas day had a low temp of 35 degrees and cool all day to have to wear a jacket!!! 6 more days left in 2014. What was your best weather memory of the year??

[snowman65]

TWC doesnt even have Houston reaching the 30's over this New Years cold front now...??

[srainhoutx]

Our rollercoaster pattern continues as temperatures have rebounded a good 25-30 degrees from yesterdays lows as a potent Winter Storm is underway across New Mexico and the Southern Rockies. The upper low bringing snow across the higher terrain of Colorado and New Mexico will shift NE today with increasing moisture streaming off the Western Gulf setting the stage for showers and eventually some storms which may approach severe limits tomorrow afternoon and evening across portions of SE Texas into SW and Central Louisiana.

12262014 SPC Day 2 day2otlk_0700.gif

12262014 10Z QPF Day 1 to 3 fd13_fill.gif

12262014 Hazards AM US.png

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.

[ronyan]

TWC doesnt even have Houston reaching the 30's over this New Years cold front now...??

I wouldn't trust a TWC forecast with an arctic front coming down. The problem is that they tend to rely (as many do) on a preset algorithm to generate forecasts from model data. Models are not handling the cold associated with this Arctic front well at this time. The high pressure system driving this front is the strongest I have observed in recent memory, and I've been model watching for 5+ years. It doesn't take that much to get Houston into the 30s during this time of the year, and what the models are showing with the HP value of 1055-1060mb coming out of Montana will easily accomplish this.

[Ptarmigan]

I wouldn't trust a TWC forecast with an arctic front coming down. The problem is that they tend to rely (as many do) on a preset algorithm to generate forecasts from model data. Models are not handling the cold associated with this Arctic front well at this time. The high pressure system driving this front is the strongest I have observed in recent memory, and I've been model watching for 5+ years. It doesn't take that much to get Houston into the 30s during this time of the year, and what the models are showing with the HP value of 1055-1060mb coming out of Montana will easily accomplish this.

I once saw TWC forecast that Houston in a deep freeze 14 days in advance. Of course that never happened.

A +1050 mb high pressure system produces very strong cold fronts as it has happened in the past.

[srainhoutx]

Folks along the Middle/Upper Texas Gulf Coast extending E into SW/Central and SE Coastal Louisiana will need to monitor for the potential of some stronger storms just offshore and possibly just inland tomorrow as the next storm system approaches.

12262014 SPC 17Z Day 2 day2otlk_1730.gif

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1058 AM CST FRI DEC 26 2014

VALID 271200Z - 281200Z

...THERE IS A MRGL RISK OF SVR TSTMS FROM THE MIDDLE/UPPER TX COAST
INTO THE LOWER MS VALLEY...

...SUMMARY...
SCATTERED THUNDERSTORMS ARE FORECAST ON SATURDAY FROM THE COASTAL
PLAINS OF TEXAS INTO THE CENTRAL GULF STATES. A FEW OF THE STRONGER
STORMS MAY POSE AN ISOLATED STRONG TO SEVERE THREAT.

...MIDDLE/UPPER TX COAST/LOWER MS VALLEY...

NEUTRAL-WEAK HEIGHT RISES WILL BE NOTED ALONG THE TX COAST INTO THE
LOWER MS VALLEY THROUGH EARLY EVENING DURING THE DAY2 PERIOD. AS A
RESULT...WARM ADVECTION WILL BE THE PRIMARY FORCING MECHANISM FOR
CONVECTIVE DEVELOPMENT...AIDED IN PART BY WEAK DIABATIC HEATING.
LATEST MODEL GUIDANCE SUGGESTS SFC FRONT SHOULD EXTEND FROM SRN
AR...SWWD INTO SCNTRL TX BY 27/18Z ADVANCING SLOWLY EAST OF THE
SABINE RIVER DURING THE LATE EVENING HOURS. FORECAST LAPSE RATES
ARE EXPECTED TO REMAIN MARGINAL DESPITE THE WEAK DIABATIC HEATING
AND THIS SHOULD LIMIT BUOYANCY FOR CONVECTION THAT EVOLVES ACROSS
THE GRADUALLY MOISTENING WARM SECTOR. WHILE DEEP LAYER SHEAR IS
EXPECTED TO BE MORE THAN ADEQUATE FOR SUSTAINING ROTATING
UPDRAFTS...WEAK BUOYANCY AND AFOREMENTIONED HEIGHT RISES SHOULD
MINIMIZE THE SEVERE POTENTIAL. FOR THIS REASON HAVE MAINTAINED 5
PERCENT SEVERE PROBS FOR LOCALLY DAMAGING WINDS AND PERHAPS AN
ISOLATED TORNADO WHERE MARITIME TROPICAL MOISTURE MANAGES TO ADVANCE
INLAND...PRIMARILY NEAR THE IMMEDIATE COAST.

..DARROW.. 12/26/2014

[srainhoutx]

The 12Z Euro is certainly not a warm look with several 1049mb+ Highs building into the front range of the Colorado Rockies extending NW into Idaho on New Year's Eve.

12262014 12Z 120 ecmwf_mslpa_namer_6.png

[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.