January: Seasonal Temps To End The Month

[Ptarmigan]

Srain, what does this mean? Can you elaborate?

Cut off low are difficult for models to handle and just how far south and how slowly they begin to move E is frequently an issue for guidance. That said in past years the Euro had a SW bias and that may well be the case. Also as we saw with the Christmas Storm, the GFS and NAM started out further N and too progressive and then flipped back to a slower and deeper trough the closer we got to Christmas Eve. Last year some improvements or upgrades were done the European Model to help with the known SW bias. While these are just computer models analyzing a tremendous amount of data we can gleam to idea as to how things may well progress. A Ridge of high pressure will build across the NE Pacific this week and the storm track will shift to that of a trough in the E. Cold air is still very present across Western Canada and we are already seeing some of that cold air slowly but surely working S of the border. Last year the non American models did rather well with a number of the cold core cut off lows that crossed N Mexico. If you recall, Midland had record snow fall events with several of these type cut off cold core lows. While it is way to early to suggest a lot of moisture, a more southerly cut off solution would tend to suggest a tap into deep tropical moisture in the Pacific and bring that moisture NE or over the Southern Rockies/Southern Plains (New Mexico/Texas/Louisiana). It is important to note that we are back in a drought situation and it would be fool hearty to suggest at this range that a big rain event is in the making. We'll just have to watch and monitor just how far S that low drops off the California/Baja Coast in the Pacific this weekend and then we'll have a fairly good idea what actual forecast or model will more correct.

Sometimes, a cutoff low can lead to heavy rain if conditions are right. The December 1991 flood occurred due to a upper level low over the Four Corners region. The heavy rain is not the largest, but over a large area that led to massive flooding.

http://www.floodsafety.com/texas/USGSdemo/patton.htm#27
http://pubs.usgs.gov/wri/wri95-4289/pdf/wri95-4289.pdf

[Andrew]

GFS tries to cut off the mid level low but never fully separates it from the trough and then shears it out throughout the central US. Slows it down in the central U.S. though before another piece of energy from the central Canada comes down. Don't think we are at the correct solution yet with the gfs.

http://www.meteo.psu.edu/~fxg1/AVN_0z/avnloopnew.html

[Andrew]

Euro is very interesting on the 00z as the colder air filters down and we have a cutoff low sit out to the west. It is probably too slow to be honest especially with such a progressive pattern but if it did happen what an event that would be for the panhandle and North Texas. Tons of potential winter precip. Something to keep an eye on. Look for a solution between the Euro and GFS. GFS is shearing the low too much while the Euro is being too slow with the overall movement.

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/ecmwfloop.html

[srainhoutx]

The ensembles continue to advertise Southern Rockies/Southern Plains event we are closely following near the New Year time frame. A Winter Storm potential that the guidance has suggested (namely the European/GEFS/SREF ensembles) with a cut off solution off the W Coast of Southern California/Baja Region. While the ensembles are a bit more progressive that the operational Euro suggests, the New Year Storm has the potential to be another high impact event. Guidance continues to advertise a Coast Low developing along the NW Gulf bring PW’s into the 2 standard deviation above normal across Texas with a potential severe weather episode developing once again in the warm sector and winter weather further N across the higher ranges of Arizona/New Mexico into the Guadalupe/Davis Mountains of Texas into the Panhandle with an ice storm potential across N Central Texas into Oklahoma. This is a low confidence forecast at this time.

The attachment 12272012 00Z Euro Ensembles 00zECMWFENS500mbHeightAnomalyNA120.gif is no longer available

[srainhoutx]

HPC Morning Update:

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
1100 AM EST THU DEC 27 2012

VALID 12Z SUN DEC 30 2012 - 12Z THU JAN 03 2013


...SYNOPSIS...

THE MEDIUM RANGE PERIOD FINDS THE NORTHERN HALF OF THE U.S. ON THE
CHILLY AND DRY SIDE...WITH A LONGWAVE TROUGH AXIS OVER EASTERN
NORTH AMERICA INTO THE WESTERN ATLANTIC...AND NEWLY DEVELOPED MEAN
RIDGING OVER THE PACIFIC NORTHWEST. ENERGY UNDERCUTTING THE RIDGE
WILL SUPPORT THE PLACEMENT OF A CLOSED LOW AFFECTING THE SOUTHWEST
STATES AND SOUTHERN PLAINS...WITH SOME INFLUENCE SPREADING
DOWNSTREAM INTO THE SOUTHEAST BY DAY 6/7.

...MODEL CHOICE...

MODELS ARE TAKING A DEEP CYCLONE FROM OFFSHORE OF NEW ENGLAND UP
INTO FAR EASTERN CANADA ON DAY 3. THE 00Z ECMWF LEANED CLOSER TO
THE COAST...AND WE PREFERRED THE TRACK OF THE GFS/UKMET...BEING
CLOSER TO CONSENSUS AND GIVEN THAT THIS SYSTEM SPINS UP RAPIDLY IN
THE WAKE OF THE PREVIOUS SYSTEM HAVING NUDGED THE BAROCLINIC ZONE
OFFSHORE. THE 00Z GFS AT 981 MB SUNDY MORNING...WAS NOT QUITE DEEP
ENOUGH. ALL THE OPERATIONAL MODELS AND ENSEMBLE MEANS TAKING THIS
LOW DOWN CLOSER TO 970 MB.

BY DAY 4 THE SYSTEM IN THE SOUTHWEST IS OUR FOCUS. THE 00Z GFS
BECAME FAST AND FLAT...AND WE DROP IT BY DAY 4. THE 00Z ECMWF WAS
BETTER UNTIL DAY 6...WHEN ITS PERFORMANCE IS MORE QUESTIONABLE
UPSTREAM IN THE PACIFIC. THE MODELS ARE STRUGGLING WITH SPLIT FLOW
IN THE EASTERN PACIFIC. TELECONNECTIONS BASED ON A PERSISTENT
NEGATIVE ANOMALY OVER NORTHERN QUEBEC WOULD FAVOR A MORE
SUPPRESSED SOUTHERN STORM TRACK THAN IS SEEN IN THE CURRENT
OPERATIONAL MODELS...WHICH ARE TENDING TO PRODUCE
PROGRESSIVE...STRONGER SYSTEMS IN A CONSOLIDATED FLOW STREAM
APPROACHING CALIFORNIA BY DAY 6/7. THUS...WE TURNED TO THE
ENSEMBLE MEANS...WHICH SHOW THIS SUPPRESSED LOOK...AND WE
PREFERRED THE ECMWF ENSEMBLE AND NAEFS...AS THE GEFS SHOWED SOME
OF THE PROGRESSIVE BIAS OF THE GFS.

...IMPACTS...

THE BLOCKY RIDGE/TROUGH COMBINATION OVER THE WEST, COMBINED WITH
THE SUPPRESSED POLAR JET OVER THE EAST SHOULD PRECLUDE WIDESPREAD,
HEAVY PRECIPITATION FOR ALL BUT THE GULF COAST STATES, WHERE WAVES
ALONG THE PRIMARY STORM TRACK SHOULD BE ABLE TO TAP GULF MOISTURE
AS THEY RIPPLE EASTWARD. HOW FAR NORTH THE PRECIPITATION GETS WITH
THESE WAVES IS DEPENDENT UPON WHERE THE CONFLUENCE RESIDES BETWEEN
THE SPLIT STREAMS. THE TELECONNECTIONS ARE DOING A GOOD JOB
DEPICTING THE EXPECTED TEMPERATURE REGIME...WITH BELOW NORMAL
TEMPS IN THE ARCTIC AIR THAT SLIPS THROUGH THE GREAT LAKES. THE
SAME TELECONNECTIONS WOULD SUGGEST LESSER PRECIPITATION CHANCE
INLAND OF THE GULF COAST. THIS IS REFLECTED IN POPS ACROSS THE
TENNESSEE VALLEY, SOUTHERN APPALACHIANS, CAROLINAS, AND MID
ATLANTIC STATES WHICH AT FIRST GLANCE APPEAR HIGH FOR REGIONS
ESSENTIALLY DOMINATED BY CONTINENTAL POLAR AIR. THE BLOCK OVER THE
FAR WEST SHOULD DEFLECT MOST OF THE SIGNIFICANT SHORTWAVES SOUTH
OF THE BORDER. THE GREAT BASIN AND NORTHERN INTERMOUNTAIN REGIONS
WILL CONTINUE TO EXPERIENCE THE CLIMATOLOGICAL TEMPERATURE
INVERSION, WITH COLD NIGHTS NEAR ZERO AND BELOW MANY AREAS.

BURKE/FRACASSO

[srainhoutx]

The Canadian has joined the Euro idea of a cut off cold core low taking a slow Southern track across Northern Mexico bringing some nasty weather across New Mexico/Texas into Louisiana.

[don]

The latest 12z Euro is more progressive, but brings an ample amount of moisture across the southern half of the state from a gulf low, going by 2m temps, and 850mb temps it seems it gets very close to having "p-type issues" as the moisture leaves on the back end of the system. fwiw

[srainhoutx]

The latest 12z Euro is more progressive, but brings an ample amount of moisture across the southern half of the state from a gulf low, going by 2m temps, and 850mb temps it seems it gets very close to having "p-type issues" as the moisture leaves on the back end of the system. fwiw

Was just about to post about the Euro, Don. Here is how I see it at this range...

The 12Z Euro suggests the cold core upper low drops S of the Great Basin and lingers. A strong cold front pushes to Coastal Texas on January 1st and stalls. The upper low is still to our W over Northern Mexico and cold air funnels S as high pressure builds across the Central Plains and a Coastal low develops in the Lower/Middle/Upper Texas Coast and begins to slowly slide ENE late January 1st and 2nd. There appears to be a lot of over running precip developing across the Southern half of Texas into Louisiana as the 500mb low slowly begins to move E. Winter weather breaks out across the Big Bend and possibly W Central Texas late on the 2nd. The wave of low pressure continues to slide S of Louisiana on the 3rd with plenty of moisture at the 700mb level across Coastal Texas. The temp anomalies are very chilly from New Years Day continuing into the days following as the upper low very slowly moves across Texas into Louisiana by the end of the first week of January. It does appear that plentiful snow falls across New Mexico as well with the potent storm system suggested by the Euro. We will see how everything unfolds over the weekend and the short wave trough drops S off/near the California Coast. It should be noted that the forecast remains very uncertain at this range.

The attachment 12272012 12Z Euro 12zeuro500mbHeightAnomalyNA096.gif is no longer available

The attachment 12272012 12Z Euro 12zeuro500mbHeightAnomalyNA120.gif is no longer available

The attachment 12272012 12Z Euro 12zeuro500mbHeightAnomalyNA144.gif is no longer available

[MontgomeryCoWx]

early cotton bowl forecast in Dallas is a 40% chance of snow showers after some early rain showers... While the game is indoors my tailgate will be whiskey and chili fueled in the jerryworld parking lot should this happen!

[don]

0z Canadian and 0z Euro look almost identical (looks to be a close call for wintry precip on both models) close but no cigars lol

[srainhoutx]

The New Years Eve/New Years Day and beyond forecast remains somewhat muddled this morning with a lot of uncertainty during the mid next week time frame. A trough is diving S this morning as seen on water vapor imagery and this is the feature that some of the guidance had attempted to cut off and develop a closed core low at the base of that trough. The GFS remains progressive and the Euro has joined the GFS solution with the first short wave progressing E, but the GFS, GGEM and Euro Ensembles as well as the Operational Euro & Canadian hold back some upper level energy with embedded short wave disturbances diving S off California and rounding the base of the trough axis that hangs back to the SW over Northern Mexico. A cold front will pass late New Years Eve/New Years Day bringing chilly air S across the Region. The fly in the ointment is the next in a series of short waves that rounds the base of the trough near Baja and ripples of upper air disturbances riding along the sub tropical jet over running the shallow cold air next Wednesday into Thursday. The GFS and Canadian suggest enough moisture and over running may create a winter weather episode while the Euro is drier and now just brings freezing temps with perhaps some high clouds across Texas/Louisiana. With the systems and short waves out over the data sparse Pacific, the forecast remains below average and will have to be fine tuned as we get closer to New Years Eve. The various NWS offices from New Mexico across Texas and Louisiana are mentioning the potential for wintry weather next week, but are not forecasting that potential due to the lack of run to run continuity of the model guidance which is understandable with all the uncertainties.

The attachment 12292012 00Z Euro Ensembles 00zECMWFENS500mbHeightAnomalyNA120.gif is no longer available

00Z Canadian:

00Z Euro:

[srainhoutx]

Morning e-mail from Jeff:

Rain is pushing offshore and into Louisiana this morning as the coastal surface trough moves ENE away from SE TX.

Overnight rainfall totals averaged generally less than .50 of an inch over much of the area with higher amounts .50 to 1 inch mainly east of I-45. Fog and low clouds continue to cover the entire region ahead of another strong cold front currently entering C TX. This front will reach the coast by late afternoon bring gusty NW winds and falling temperatures along with clearing of the fog and clouds out of the area.

Cold tonight even with the wind staying gusty with lows in the 30-35 range across the area and highs on Saturday only in the low to mid 50’s under sunny skies. Light freeze most areas Sunday morning 29-32 with highs back into the upper 50’s.

Changes begin to take shape on Sunday afternoon as the next powerful storm system in this progressive split flow pattern enters into the SW US. Moisture will surge northward from S TX on Sunday as a warm front begins to advance northward. Expect a rapid influx of low clouds similar to yesterday with light rain and fog advancing northward ahead of the warm front on Sunday evening. Moisture values really ramp up Sunday night with very healthy PWS forecasted into the region by early Monday…nearing record levels for this time of year. Large scale lift will be increasing late Sunday into most of Monday as the upper trough advances eastward into the southern plains and surface low pressure develops along the warm front and moves up the coast. Still too early to determine if and/or how far inland the warm front may penetrate, but areas along this feature could have a severe weather threat. As suspected yesterday the more progressive GFS model was the correct line of thinking with this system as the ECMWF has trended in that direction. With the more progressive solution, expect widespread rains on Monday followed by a line of thunderstorms Monday night/early Tuesday. Some of the storms could be severe with damaging winds and tornadoes along with very heavy rainfall.

This leading short wave will force a strong cold front through the region on New Year’s Day, but the main upper trough looks to linger back SW of the area into N MX keeping a SW flow aloft over the surface cold dome…an overrunning pattern. Both the GFS and ECMWF generally agree with this thinking, but the ECMWF is more closed off with the main upper trough and colder compared to the GFS. Do not think clouds will clear out much behind the frontal passage early New Year’s Day and it is possible that a very cold rain could develop on Wednesday into Wednesday night. Will need to keep a close eye on low temperatures both Wednesday and Thursday mornings for our N and W counties as they will be nearing freezing with some chance of potential rain.

[srainhoutx]

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
1047 AM EST FRI DEC 28 2012

VALID 12Z MON DEC 31 2012 - 12Z FRI JAN 04 2013

...SYNOPSIS/IMPACTS...

THE NATION WILL NOT SEE ANY LARGE SCALE CYCLOGENESIS IN DAYS 3-7.
THE POLAR FRONT WILL SPEND MUCH OF THE PERIOD SINKING THROUGH THE
GULF COAST STATES AND INTO THE GULF/FLORIDA. THE ARCTIC FRONT WILL
SPEND MUCH OF THE PERIOD STRETCHED FROM THE MID ATLANTIC TO THE
MIDWEST AND CENTRAL/NORTHERN PLAINS. UPPER LEVEL RIDGING BUILDING
OVER THE NORTHERN ROCKIES WILL SPLIT THE UPPER FLOW
PATTERN...TAKING SYSTEMS AROUND THE WESTERN U.S...AND PROMOTING
FAVORABLE CONDITIONS FOR RADIATIONAL COOLING AT NIGHT...AND FOR
MOUNTAIN/VALLEY EFFECTS TO STRONGLY INFLUENCE DIURNAL
TEMPERATURES. ENERGY UNDERCUTTING THE RIDGE WILL YIELD A COUPLE OF
CLOSED LOWS OVER THE SOUTHWEST U.S...WITH PRECIPITATION EXTENDING
DOWNSTREAM INTO THE SOUTHERN PLAINS/SOUTHEAST. GIVEN THE INITIAL
SUPPLY OF DRY AND COLD AIR...A TRANSITION ZONE TOWARD WINTRY
PRECIPITATION WILL BE LIKELY WITH THE FIRST SYSTEM MONDAY/TUESDAY.
PRECIPITATION AMOUNTS DO NOT APPEAR HEAVY...THOUGH...AS SHORTWAVES
WILL TEND TO SHEAR/DE-AMPLIFY AS THEY HEAD INTO CONFLUENT FLOW
EAST OF THE PLAINS. FINALLY...MODELS CONTINUE TO SUGGEST THAT A
CLOSED LOW WILL REACH A CALIFORNIA BY NEXT THURSDAY OR FRIDAY.

...MODEL CHOICE...

MODEL AGREEMENT WAS GOOD THROUGH EARLY DAY 5. THEN THE GFS
DISPLAYS A TENDENCY TOWARD FLATTER FLOW AND FASTER
PROGRESSION...AS IT HAS DONE CONSISTENTLY THIS WINTER ON THE LARGE
SCALE. KEEPING WITH CONTINUITY...AND WITH THE SUPPORT OF
TELECONNECTIONS BASED ON A NEGATIVE ANOMALY OVER QUEBEC...WE
WEIGHTED THE FORECAST TOWARD THE ECMWF ENSEMBLE MEAN AND TO A
LESSER EXTENT THE NAEFS ENSEMBLE MEAN. FOR THE SMALLER SCALE
DETAILS WE INCLUDED INFLUENCE FROM THE 00Z ECMWF AND 00Z CANADIAN.
WE ARE LESS CONFIDENT IN THE SHORTWAVE DETAILS GIVEN THE LOW
AMPLITUDE OF WAVES IN THIS PATTERN...BUT THE ECMWF AND CANADIAN
ARE CLOSE TO THE ECMWF ENSEMBLE MEAN FOR THE MAJORITY OF THE
TIME...AND THEY FIT OUR EXPECTATION FOR THE TIMING AND LOCATION OF
THE SYSTEM APPROACHING CALIFORNIA ON DAY 6/7.

BURKE/FRACASSO

[srainhoutx]

The trends so far today via the GFS ensembles and the Canadian suggest a stormy New Years Eve/New Years day. There are also growing indications that a cut off low will develop S of the Great Basin by next Tuesday (New Years Day) and continue to bring several upper air disturbance across New Mexico and Texas into Louisiana as a Coastal low develops along the S Texas Coast along a stalled Canadian cold front bringing over running moisture over the shallow very chilly cold air mass at the surface. While it is too soon to know with any certainty, that is the recipe for all sorts of winter weather mischief as well as an ice storm threat, should it verify. We’ll need to monitor the trends for next Wednesday into Thursday in the days ahead.

12Z GEFS Anomalies:

The attachment 12282012 12Z GEFS 12zgfsensembles500mbHeightAnomalyNA120.gif is no longer available

The attachment 12282012 12Z GEFS 12zgfsensembles500mbHeightAnomalyNA144.gif is no longer available

12Z Canadian:

[don]

Just checked the 12z Euro and it shows a pretty good,probably icing event for the southern half of the state, looks like even southeast Texas gets in on the action on the tail end of the moisture.

[srainhoutx]

Just checked the 12z Euro and it shows a pretty good,probably icing event for the southern half of the state, looks like even southeast Texas gets in on the action on the tail end of the moisture.

[harpman]

I must ask what does this mean for southeast La. ? I follow this forum regularly and rarely ask an opinion for my area. But I was just curious in this instance. Thanks.

[srainhoutx]

I must ask what does this mean for southeast La. ? Thanks.

It is still too soon to know with any certainty how this will actually evolve. That said the trends do raise an eyebrow for a potential severe weather late New Years Eve/early New Years Day with some potential for over running moisture if the Canadian front stalls close to the Coast and a wave of low pressure actually develops near the Rio Grande Valley and slides ENE along that boundary.

HPC Surface Charts just issued for the time frame in question...

[harpman]

Thanks, Srain. Much appreciated. I was wondering about frozen precip this far to the east of you guys.

[weatherguy425]

For once, I actually would like for he closed low o ravel just a ad further north, putting Lubbock in more of he sweet spot vs. Midland/Odessa. ha said, even GFS begins precip as snow with lead disturbance on Sunday nigh in west Texas.