November 2015: Ending Cold & Rainy

[srainhoutx]

Lengthy and detailed evening briefing from Jeff:

Potential for high impact storm system next Monday and Tuesday.

Yet another El Nino enhanced storm system will move into the SW US and then eastward across TX early next week. Forecast models continue to show an impressive upper level storm system and very strong surface low to affect the state early next week. Sub-tropical jet will remain in place over TX this weekend with a disturbance currently over MX likely to move across the area on Friday…it should be too dry at the surface for any rainfall.

Upper level system will drop down the US west coast and into the SW US on Sunday and really begin to intensify. This intense deep longwave trough will force strong surface pressure falls over NW TX Sunday night into Monday with an impressive mid-November cyclone developing over the central and southern plains. Strong low level jet of 40-60kts develops over coastal TX Monday transporting significant deep layer moisture northward. Upper jet stream is overhead and expect thunderstorms to erupt Monday afternoon in a very highly sheared air mass. Low level jet will be crossed with a powerful 90-120kt mid level jet stream over the area resulting in strong veering of the wind field with height and strong vertical shear. Forecasted low level shear parameters for late Monday into next Tuesday are impressive. Main question is the amount of instability in the warm sector over the region. Dewpoints likely to surge into the lower 70’s and with strong mid level cooling likely as the strong upper level trough tilts negative allowing the mid level cold pool to eject across the warm sector resulting in good instability. Parameters are certainly pointing toward a potentially significant severe weather episode…including tornadoes given all the wind energy…this is something that needs to be watched very closely over the coming days. Some of our worst tornado outbreaks in SE TX have been in the month of November and the worst was in November 1992 when multiple strong tornadoes including a F4 moved across Harris County. Parameters become even more favorable early Tuesday morning with a strong cold front slicing into a highly sheared and moderately unstable air mass. Upper jet goes into a strong split structure over SE TX allowing good lift of the pre-frontal air mass. A squall line with wind damage will be possible along with discrete supercells ahead of the line. If these supercells root near the surface they will likely become tornadic given the strongly sheared air mass.

Moisture advection and low level inflow will be very impressive on Monday and Tuesday ahead of the cold front. Concern for discrete supercell formation in the warm sector with both a severe and flash flood threat. While system looks overall progressive, potential for supercell training could allow rapid build up of rainfall totals as well as multiple rounds of severe weather. Similar event setup on 11-17-2003 which resulted in multiple tornadoes and flash flooding from several training HP supercells over Fort Bend and Harris Counties. Moisture levels peak around 1.8-2.0 inches which is near maximum levels for mid November. Storms will certainly be capable of some intense rainfall rates.

This system deserves attention over the next 72 hours as impacts across much of east TX Monday and Tuesday could be significant.

Very cold air mass surges down the backside of this system with blizzard conditions likely from Colorado into the TX panhandle and eastward into the plains. Cold air mass will plow southward over TX behind the storm system on Wednesday. Secondary potential stronger surge of modified arctic air appears poised to blast southward toward the end of next week with very cold temperatures possible by the weekend before Thanksgiving. ECMWF 850mb temperatures running some significant cold anomalies for that time period…so something to watch.

[Ptarmigan]

Next week could be interesting. 1992, 2003, and 2004 had severe weather. 1992 and 2004 were El Nino. 2003 was Neutral.

[Katdaddy]

A few sprinkles, patches of very light rain, and virga this morning across portions of SE TX will move into LA this evening. Expect more clouds than sun this weekend with some slight rain chances Saturday night and Sunday as a very powerful upper trough approaches TX from the W. Severe weather including tornadoes and flooding continue to look possible for SE TX Monday through Wednesday. The SPC has a large 15% hatch area for portions of TX during the Monday through Wednesday timeframe.

From this morning's Houston-Galveston AFD:

FOCUS FOR NEXT EVENT WITH SEVERE AND HEAVY RAINFALL/FLOODING WILL BE IN THE MONDAY THROUGH WEDNESDAY PERIOD. AT PRESENT IT APPEARS
THAT SETX WILL HAVE A THREAT OF SEVERE/STRONG THUNDERSTORMS (WINDS/TORNADIC) IN A HIGH TO VERY HIGH SHEAR/LOW CAPE ENVIRONMENT MONDAY AFTERNOON AND NIGHT TRANSITIONING TO HIGH EFFICIENCY HEAVY RAIN THREAT WITH CONTINUED SEVERE TORNADIC TUESDAY MORNING. WIND PROFILES ARE LOADED WITH SURFACE WINDS OF 15-20MPH SUSTAINED WINDS AND LLJ OF 30-55 KNOTS. TUESDAY AFTERNOON THROUGH WEDNESDAY GETS VERY PROBLEMATIC WITH THE TRACK/SPEED OF THE UPPER TROUGH WHICH
MAY BE SLOWER THAN CURRENT MODEL CONSENSUS WHICH KEEPS A HEAVY RAIN THREAT FOR THE EASTERN HALF OF THE REGION WELL INTO WEDNESDAY. CONFIDENCE/AGREEMENT IN SOLUTIONS IS MODERATE THROUGH TUESDAY BUT WEDNESDAY AND BEYOND IS LOW AT BEST.

[srainhoutx]

The late morning Updated Extended Range Discussion still advertise a big late Fall/early Winter Storm wrapping up across the Southern Plains early next week. As the week progresses, attention turns to the Aleutians and the Gulf of Alaska as well as the Pacific where a long stream of moisture extends Hawaii and ripples of disturbed weather march toward yet another developing Western Trough. Cold air that has been building across Siberia may be dislodged sending a piece of that Arctic Cold South into Western Canada and modifying as it settles into the Great Basin and Plains.

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1059 AM EST FRI NOV 13 2015

VALID 12Z MON NOV 16 2015 - 12Z FRI NOV 20 2015

...HEAVY RAIN LIKELY FOR THE MIDDLE AND LOWER MISSISSIPPI RIVER
VALLEY NEXT TUE/WED...

...SIGNIFICANT SNOW POSSIBLE FOR PORTIONS OF EASTERN COLORADO AND
PERHAPS WESTERN KS/NE TUESDAY...


...OVERVIEW...

PATTERN WILL FEATURE A STRONG UPPER TROUGH DIGGING THROUGH THE
FOUR CORNERS REGION AND LIFTING THROUGH THE SOUTHERN AND CENTRAL
PLAINS NEXT WEEK. RIDGING OVER THE EASTERN CONUS SHOULD ONLY
SLOWLY RETREAT INTO THE WESTERN ATLANTIC WHICH PUTS A HALT ON THE
EASTWARD PROGRESSION OF THE SYSTEM. IN THE PACIFIC... THE MODELS
AND ENSEMBLES STILL STRUGGLE TO HANDLE THE DETAILS OF THE FLOW BUT
DO POINT TO INCREASED RIDGING MOVING ACROSS THE ALEUTIANS INTO THE
GULF OF ALASKA MID-LATE WEEK NEXT WEEK... WHICH SUPPORTS ANOTHER
TROUGH MOVING THROUGH THE INTERIOR WEST INTO THE CENTRAL PLAINS.


...GUIDANCE ASSESSMENT...

WITH RESPECT TO THE EVOLVING UPPER LOW EJECTING OUT OF THE
SOUTHERN PLAINS... THE GFS REMAINS SLOWEST AND MOST CLOSED OFF
COMPARED TO THE OTHER MODELS/ENSEMBLES AND FALLS ON THE SW SIDE OF
THE SPREAD. THE OVERALL TREND... ESPECIALLY FROM THE ECMWF
ENSEMBLES... HAS BEEN A SLOWER AND DEEPER SYSTEM COMPARED TO 24HRS
AGO... BUT THIS FALLS BACK IN LINE WITH THE AGREEMENT SEEN 48 HRS
AGO. HOWEVER... STILL FEEL THAT THE SLOW GFS IS TOO SLOW TO LIFT
THE SYSTEM NORTHEASTWARD MIDWEEK NEXT WEEK AS UPSTREAM ENERGY
SHOULD BE ENOUGH OF A KICKER TO PUSH THINGS ALONG. HOWEVER... THIS
IS CONTINGENT UPON THE MODELS GETTING THE FLOW ACROSS THE
NORTHEAST PACIFIC CORRECT NEXT MON-TUE WHICH IS NOT A GUARANTEE.
WITH THE ECMWF/CANADIAN/UKMET FORMING A GOOD OPERATIONAL MODEL
CONSENSUS ON A FASTER THAN THE GFS SOLUTION... FELT COMFORTABLE
SIDING NEAR THEIR SOLUTIONS WHICH ALSO ALIGNS WITH A 00Z
GEFS/ECENS COMPROMISE SOLUTION ESPECIALLY NEXT WED. THEREAFTER...
USED THAT ENSEMBLE MEAN BLEND TO ROUND OUT THE FORECAST AS THE
SPECIFICS ARE PRETTY MUDDIED.


...SENSIBLE WEATHER HIGHLIGHTS...

THREATS IN THE MEDIUM RANGE INCLUDE...

HEAVY RAIN - SURFACE LOW AND COLD/WARM FRONT WILL LIFT
NORTHEASTWARD FROM SE CO ON MON THROUGH KS/OK AND INTO NE/IA
TUE-WED. COMBINATION OF SUBTROPICAL JET ACROSS MEXICO... SOUTHERLY
FLOW OUT OF THE GULF OF MEXICO -- ABOUT 55KTS AT 850MB... AND PW
VALUES RISING TO BETWEEN 1.50-2.00 INCHES -- ABOUT 2-4 STANDARD
DEVIATIONS ABOVE AVERAGE... SUPPORTS AN EXPANSIVE HEAVY RAINFALL
THREAT FROM E TX INTO LA NORTHWARD THROUGH AR/MO AND SOUTHERN
ILLINOIS AHEAD OF THE STORM SYSTEM. SEVERAL INCHES ARE POSSIBLE
WITH SOME WETTER ENSEMBLE MEMBERS NEAR/OVER 10 INCHES OVER 48-60
HOURS.

SNOWFALL - COLD ENOUGH AIR SHOULD BE IN PLACE FOR AN AREA OF HEAVY
SNOW ON THE NW SIDE OF THE UPPER/SFC LOW. EASTERN COLORADO STANDS
THE BEST CHANCE FOR SIGNIFICANT SNOW AND THIS MAY SPREAD
NORTHEASTWARD AS THE LOW PUSHES AWAY. EXACT SPEED OF THE SYSTEM
AND OTHER FACTORS WILL INFLUENCE TO WHERE THE SNOWFALL THREAT WILL
SPREAD.

SEVERE WEATHER - THE STORM PREDICTION CENTER STILL HIGHLIGHTS
TEXAS INTO LOUISIANA FOR SEVERE WEATHER MON INTO TUE. PLEASE
CONSULT THEIR DISCUSSION FOR MORE DETAILS.

ADDITIONAL RAINFALL IN THE PAC NW LATER NEXT WEEK SHOULD BE
TYPICAL ENOUGH TO BE OF MINOR CONCERN... DEPENDING ON HOW THE
RIVERS RESPOND TO AND REBOUND FROM THE SHORT TERM HEAVY RAINFALL
THE NEXT COUPLE OF DAYS.


FRACASSO

[srainhoutx]

The 12Z Global guidance remains in good agreement through next Tuesday morning developing a powerful Southern Storm. There are some differences that will need to be monitored beyond Tuesday as to how this storm meanders in the Plains. If the system moves out to the NE quicker, the frontal boundary will likely push East of our Region lessening the threat for a significant heavy rainfall event. Should the storm system linger, a slower frontal boundary could setup training very heavy thunderstorms somewhere over portions of the Eastern half of Texas into Louisiana.

[snowman65]

What kind of temps are we looking at behind the system? My Bday is the 18th and would like to see some colder temps that day please

[wxman57]

Here's a meteogram from the 12Z GFS, snowman. I think you'll be seeing cooler temps behind Tuesday's cold front. Not nearly as cold as last Nov. 18th (freezing), but cool-ish.

[srainhoutx]

Afternoon Updated 5 Day QPF has been issued.

[snowman65]

Good enough for me! Thanks!

[srainhoutx]

For those wondering about the Thanksgiving Week Holiday Period, The Climate Prediction Center is suggesting cooler and wetter weather across our Region.

[srainhoutx]

Looking further out to the end of November and the beginning of December, the Climate Prediction Center in the Friday afternoon Updated Experimental Week 3 to Week 4 Outlook suggests more of the same.

[srainhoutx]

Friday evening briefing from Jeff:

Powerful storm system to affect TX early-mid next week…with potential widespread tornado/severe weather outbreak and flash flooding.

Sub-tropical jet continues over TX with mid and high level clouds in place. Dry low levels will keep any radar returns from reaching the ground on Saturday with temperatures on the cool side.

Big changes come Sunday into Monday as an intensifying upper level storm system ejects eastward out of the southern Rockies and into the southern plains. Surface pressure falls over NW TX will rapidly develop into an intense surface cyclone by late Monday with an impressive 40-55kt low level jet developing inland over coastal and east TX. Tremendous moisture advection will occur with dewpoints rising into the lower 70’s by late Monday. Embedded disturbances in the sub-tropical flow and increasing diffluent upper level winds on the east side of the trough will result in a gradual increase in showers and thunderstorms Monday afternoon and evening. May see enough instability and shear for a few severe thunderstorms by Monday afternoon… and this would be the start of a prolonged severe weather and potential tornado outbreak.

Tuesday:
Significant weather day possible with widespread severe/tornado threats and flash flooding.

Surface low really deepens over the plains with pressure falling toward 990mb (near category 1 hurricane intensity). Powerful upper level jet core will carve into central and SE TX early Tuesday upwards of 120kts overtop of the 40-50kt low level jet. This will lead to tremendous speed and directional wind shear. Air mass will be warm and very moist and position of the upper level trough will likely advect a cold pool aloft over this warm surface air mass resulting in increasing instability. Forecasted CAPE values of 1000-2000 J/kg will be possible and when combined with the load wind profiles…is very concerning with respect to the tornado threat. Upper jet goes into a strong split structure overtop of the warm sector air mass and this may be the catalyst for discrete supercell formation by early Tuesday. Given the shear profiles any discrete supercells rooted near the surface will be rotating and have an enhanced tornado risk especially when coupled with very low LCL’s (cloud bases). Forecasted low level hodographs are strongly curved suggesting a good environment for tornado formation. Need to get closer to the event to see some of the other tornado indices, but what is available now is looking pretty rough.

Cold front comes slicing into the juicy air mass during the day and expect more severe weather with a squall line and possible supercells within the line. Damaging wind threat appears likely with any squall line as mid level wind energy gets transported toward the surface.

Increasing concern with the flash flood threat also as wind fields will support repeat cell training of potential HP supercells. Moisture values rise to 1.8-2.0 in PWS by early Monday which is +2 SD above normal for November. Saturated profile will result in very efficient rainfall production with hourly rates of 2-3 inches possible. Potential for training bands and repeat supercells impacts is certainly raising the flash flood threat. Will go 2-3 inches widespread for now with isolated 5 inches. Models trying to slow the upper level system down some and maintain a an excessive rainfall threat into Tuesday night and even Wednesday which would be very concerning. Not overly confident in the slower solution nor being able to maintain excessive moisture as expect a strong dry slot to round the base of the trough and some point Tuesday helping to end the rainfall. Will have to watch this potential very closely over the weekend.

Residents should be prepared for active weather from late Monday afternoon-early Wednesday morning with Tuesday likely being the worst day. Potential for tornadoes, damaging winds, large hail, and flash flooding during that time period.

[Katdaddy]

A significant severe weather event still on track for Monday and Tuesday across SE TX.

[srainhoutx]

We are still a day or two out before we can nail down the severe parameters, but each successive model run continues to advertise a tremendous amount of wind energy associated with this Southern Storm. It is worrisome to see veering winds at the upper and lower levels and a powerful jet stream interacting as the surface low wraps to a sub 990mb bomb across the Plains. All modes of severe weather still appear to be on the table during the daylight hours of Tuesday.

[Ptarmigan]

I can see shades of November 17, 2003.

[cperk]

I can see shades of November 17, 2003.

Care to elaborate.

[jasons2k]

I can see shades of November 17, 2003.

Care to elaborate.

From Jeff's update on 11/12 (few pages up):
" Similar event setup on 11-17-2003 which resulted in multiple tornadoes and flash flooding from several training HP supercells over Fort Bend and Harris Counties."

Also, found this in an old thread:
"Down here, there was also another outbreak in November of 2003. 32 tornadoes were reported between 9 AM and 6 PM on November 17,2003, with several F-2. One F-2 that hit the Sugar Land area caused over 50 injuries if I remember correctly."

http://forums.khou.com/viewtopic.php?f=2&t=285&start=10

[cperk]

I can see shades of November 17, 2003.

Care to elaborate.

From Jeff's update on 11/12 (few pages up):
" Similar event setup on 11-17-2003 which resulted in multiple tornadoes and flash flooding from several training HP supercells over Fort Bend and Harris Counties."

Also, found this in an old thread:
"Down here, there was also another outbreak in November of 2003. 32 tornadoes were reported between 9 AM and 6 PM on November 17,2003, with several F-2. One F-2 that hit the Sugar Land area caused over 50 injuries if I remember correctly."

http://forums.khou.com/viewtopic.php?f=2&t=285&start=10

Much appreciated jasons.

[srainhoutx]

The overnight guidance continues to advertise active weather days Monday to our N and W into Tuesday when portions of Central, East, NE and SE Texas into Western Louisiana are under the gun with the primary severe weather threat being Tornadoes, damaging winds and isolated heavy rainfall. A slow moving squall line should be advancing East early Tuesday morning from Central Texas possibly reaching Metro Houston during peak heating. Any discrete rotating super cells developing ahead of the main squall line will be capable of rotating updrafts from veering wind profiles as a deepening surface low bombs out near Western Kansas. 1 to 3 inches of heavy rainfall is possible as the squall line advance East with isolated higher amounts of 4 to 5 inches of rain falling in short order in the more intense thunderstorms. Stay weather wise Monday into Tuesday night folks. This strong storm system appears to be a harbinger of a pattern change that will continue into the busy Thanksgiving Holiday travel period.

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Potential Thanksgiving Southern Storm:

[unome]

was surprised to see this on Mark Sudduth's Twitter feed: https://twitter.com/hurricanetrack/stat ... 6350895104

Mark Sudduth
‏@hurricanetrack

Moving equipment in to Houston to help monitor three area bayous during next week's storm system that is expected to bring flooding rains.