November 2015: Ending Cold & Rainy

[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.

[srainhoutx]

Morning briefing of Jeff:

Strong storm system digging into the SW US will bring highly active weather to TX Monday and Tuesday.

Risks are severe weather including damaging winds and tornadoes and heavy rainfall.

Upper level storm system and deepening upper level trough over the Rockies will eject into the plains Monday and Tuesday. Strong pressure falls over NW TX late today will force surface low pressure which will rapidly deepen as it moves NE toward KS on Monday into Tuesday. A strong cold front will blast SE across TX late Monday into Tuesday with a significant temperature gradient across the state by Tuesday morning. This system features fairly impressive dynamics and wind energy aloft and this will likely translate into a severe weather outbreak over portions of TX Monday afternoon through the day on Tuesday.

Monday:
Dry low level air mass in place will begin to undergo moistening tonight as coastal warm front begins to work northward. High resolution guidance is slow in advancing this boundary northward on Monday and keeps dewpoints in the upper 50’s and lower 60’s. The pace of northward movement will likely become a function of how much shower and thunderstorm development occurs along and north of the boundary. Models are not overly aggressive with development on Monday, but factors will be coming together including an increasing warm advection pattern coupled with weak disturbances moving across the area in the flow aloft from the SW. Severe parameters look week on Monday with only modest low level wind shear in place. Think there could be some strong storms, but severe weather looks less likely.

Monday night:
Strong low level jet will be in place with increasing wind fields aloft as the core of a 120kt upper level jet streak moves into C TX. Upper winds become increasingly diffluent (spreading apart) which will enhance the lift over the area. New development in some of the latest model runs is a slight veering of the low level wind field to the SSW which may advect a mid level capping inversion NE into portions of SE TX. This could help to prevent warm sector storm development on Monday night, but it is uncertain exactly how far NE this capping may extend into the area and if the increasing lift approaching from the west could erode any capping. With increasing wind profiles severe thunderstorms would be possible if they were to develop within the warm sector.

Tuesday:
Highly moist and moderately unstable air mass will be in place by Tuesday morning. Strong cold front will be located along I-35 by early morning (600am) and progress eastward into SE TX throughout the day. Expect a strong squall line of thunderstorms to exist along this front with severe weather likely. Air mass over SE TX will warm into the mid 70’s to low 80’s resulting in building instability ahead of the front with CAPE of 1000-1500 J/kg. Low level wind fields certainly show a significant degree of turning with helicity values of 200-400 m^2/s^2 over SE TX. Strong wind energy both near the surface and aloft will support a damaging wind threat with any of the storms. Linear forcing along the cold front will likely maintain the squall line across the region with wind damage the main threat with the line. May see a few discrete cells develop ahead of the main line and these storms could become tornadic with all the low level turning in place. May also see weak short lived tornadoes along the main squall line. Expect the cold front to reach our western counties in the 800am-1000am time frame and into the central counties (metro Houston) between 1000am and 300pm and then exit our eastern counties between 200pm and 600pm.

High moisture levels will accompany this storm system with PWS rising to near 2.0 inches by early Tuesday morning. Excessive rainfall will be likely with the strongest storms with rainfall rates of 2-3 inches per hour. Overall fast forward progression of the cold front and thunderstorms should help to negate a significant flash flood threat however urban ponding on roadways will be possible as the storms move across the region. Still concerned for a period of possible cell training of thunderstorms early Tuesday morning ahead of the main squall line which could add up rainfall totals, but this threat is conditional on actual develop over the warm sector which becomes a function of the mid level capping intensity. Widespread rainfall amounts of 1-2 inches are likely with isolated amounts of 3-5 inches. The heaviest rainfall will likely be NE of a line from College Station to Conroe to Liberty.

Coldest air of the fall season will usher into the region behind the Tuesday afternoon frontal passage. Temperatures will fall from the 70’s into the 60’s and may be even the 50’s post front. Lows Wednesday morning will likely fall into the 40’s over much of the region. High pressure builds into the region Wednesday-Saturday with cool morning lows in the 50’s and highs in the 70’s.

Next storm system looks like another potential big weather maker for the week of Thanksgiving as it takes a similar low latitude route and entrains a good chunk of cold air. This time period is still out there in the longer range…but it looks cold and potentially wet for much of Thanksgiving week.

SPC Severe Weather Outlook for Tuesday:

[unome]

a couple snippets from "replies": https://twitter.com/hurricanetrack/with_replies

• Going to be coordinating with HCFCD to help them with real time video.
  
  they want to see real-time verification of what the gauges show and we have the answer to that

very cool that they're working together, he does that a lot with local emergency ppl in various states

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.

[srainhoutx]

The SPC has expanded the Day 2 Slight Risk for severe storms to include portions of SE Texas and Metro Houston.

[Andrew]

Tx tech WRF shows some pretty impressive updraft helicity values with the line of storms tomorrow across the panhandle. EHI and low level shear in particular look very promising for both straight line winds and embedded tornadoes. Closer to home, straight line winds look to be the largest area of concern but if we are on the tail end of the line, don't be surprised if we see a couple of tornadoes spin up. I wouldn't be shocked if we see some sort of moderate risk issued for tomorrow afternoon.

[srainhoutx]

The morning Updated Weather Prediction Center Excessive Rainfall Outlook now includes a Slight Risk for Excessive Rainfall for portions of SE Texas and most of Louisiana.

[Katdaddy]

The well advertised severe weather event to unfold across Central and NW TX this afternoon and then develop E and SE tonight across South Central, SE and E TX. Thunderstorms near the warm front across S Central and SE TX could have brief spin ups due to low level helicity this afternoon however the real concern for SE TX arrives after midnight through Tuesday afternoon. Helicity peaks between 3AM and noon with the highest threat for tornadoes ahead of the front. As the front arrives the threat will transition to damaging straight line winds as well as heavy rains. If we get a little heating tomorrow the severe weather threat will increase significantly. The severe weather and heavy rains look to push into LA between 4PM and 8PM tomorrow. A rough 12-24 hours on the way so be weather aware from this afternoon through Tuesday afternoon.

[srainhoutx]

Monday morning briefing from Jeff:

Strong storm system approaching TX.

Severe thunderstorms and heavy rainfall likely tonight and Tuesday.

A powerful upper level low pressure system over the SW US will begin to move eastward today and tonight and into the central plains on Tuesday. Strong height falls are in progress over NW TX this morning and are helping to develop surface low pressure. This low pressure will deepen today as it tracks NNE and draws a strong old front southward across W TX. Over SE TX a maritime warm front has formed off the upper TX coast with a moist a tropical air mass south of this boundary and modified tropical air mass inland over SE TX. Low clouds and fog have developed north of the warm front and this will likely prevent a quick northward movement of the boundary today.

Upper winds are starting to diverge over SE TX and water vapor images show a large mass of moisture and likely a couple of disturbances heading out of MX toward TX. Expect increasing lift coupled with the warm front to begin to develop showers and possibly even a few thunderstorms this afternoon. Backed low level winds (ESE) near/just north of the warm front become SSW winds around 4000 ft yielding good low level turning. Instability is weak with the cloud cover and fog, but wind shear is impressive so will need to watch any storms that develop near the warm front this afternoon and evening for a tornado threat.

Late Tonight/Tuesday:
Wind profiles really increase in the 300am to noon time period with strong turning over the warm sector. High resolution models now showing more development of storms (possibly supercells) in the warm sector air mass and these storms will have a higher tornado potential. Linear forcing on surging cold front will develop a broken line of strong to severe thunderstorms across C TX between midnight and 600am with this line moving east across SE TX on Tuesday morning into the afternoon hours. Severe threat will transition from a higher tornado threat in the morning hours to damaging straight lines in the mid morning to mid afternoon hours. Current forecast as the front through much of the area by early to mid afternoon, but any slowing of the boundary and/or greater heating toward 80 degrees on Tuesday will result in a much more significant severe weather/tornado threat. Modest instability is the only factor keeping things from really getting out of control on Tuesday as wind profiles will be scary.

Moisture really ramps up this evening with surge of tropical air mass south of the warm front pouring into the region around sunset. Moisture level reach near record levels by late this evening and expect excessive rainfall in any of the stronger storms. A little more worried with models showing more warm sector development overnight now than yesterday which could add up rainfall totals prior to the main squall line reaching the area. Will maintain a solid 1-2 inches with isolated totals of 3-4 inches…much of which could fall in an hour or 2. Street flooding will be the main threats with the high hourly rainfall rates.

Cool and dry conditions for the rest of the week with potentially cold and stormy weather returning for the week of Thanksgiving.

[srainhoutx]

For what it's worth, the 12Z NAM suggests the upper trough may be a bit slower ejecting out of New Mexico/West Texas meaning that the progression of the squall line could be a bit slower and later in the afternoon/early evening across SE and East Texas. The NAM also suggests a bit more of a neutral tilted trough that raises an eyebrow concerning the severe potential we may see across the Region.

[tireman4]

Please be weather wary folks. This will be an ever changing event and being alert part of the process. Stay tuned to this forum and your local media outlets.

[tireman4]

HGX AFD this morning:


FXUS64 KHGX 161051
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
451 AM CST MON NOV 16 2015

.DISCUSSION...
SEVERE WEATHER THREAT STILL ON FOR MAINLY TUESDAY.

SOME VIRGA MOVING INTO THE AREA FROM THE WEST AND MAY GET SOME
PATCHY LIGHT RAIN OUT OF IT BUT MORE LIKE A TRACE OR LESS.
TEMPERATURES IN THE LOWER 60S INLAND AND 65-71 COAST. TEMPERATURES
RISING IN THE COASTAL COUNTIES. 24 HR TEMPERATURE CHANGES OF 4 TO
11 DEGREES FROM YESTDAY MORNING AT THIS TIME. COASTAL TROUGHING
APPARENT ON 08Z ANALYSIS AND WARM FRONT APPEARS TO BE 20-40NM
OFFSHORE LIFTING NORTHWARD. EXPECT THAT WARM FRONT TO SLOW AS IT
NEARS THE COAST THEN LIFT NORTH THROUGH THE REGION TODAY. TODAY
SHOULD SEE SCATTERED SHOWERS ACROSS THE AREA THROUGHOUT THE DAY
BUT MAINLY AFTER 9 AM...WITH ISOLATED TO SCATTERED THUNDERSTORMS
THIS AFTERNOON. BETTER CHANCES FOR THUNDERSTORMS WILL BE NORTHWEST
OF A LINE FROM BAY CITY TO GROVETON THIS AFTERNOON. WIND PROFILES
FROM AMDAR/MODELS/UA SHOWING THE BEGINNING OF A STRONGLY VEERING
WIND PROFILE EASTERLY AT THE SURFACE AND 30-35KTS AT 4KFT FROM THE
SSW. ALTHOUGH THE CAPE MAY BE SLIM TODAY FOR MUCH OF THE DAY THE
WIND PROFILES WILL POSE AN ISSUE WITH LOW LEVEL HELICITY. CAN`T
RULE OUT A BRIEF SPIN UP FUNNEL CLOUD OR EVEN A TORNADO MAINLY
NEAR THE WARM FRONTAL BOUNDARY. IMPRESSIVE UPPER LEVEL TROUGH WILL
SLIDE EAST THROUGH THE NIGHT AND WILL BRING THE UPPER JET INTO THE
REGION WITH INCREASING SYNOPTIC SCALE LIFT. A COLD FRONT SHOULD
MOVE THROUGH WEST TEXAS EARLY THIS EVENING AND THE HILL COUNTRY
MIDNIGHT TO 6 AM ARRIVING IN SETX PERHAPS AS EARLY AS 6 AM
TUESDAY. OVERNIGHT THOUGH SETX WILL BE UNDER INCREASING LL FLOW
WITH INCREASING HELICITY WITH SOARING P.W. OF 1.8-2.2" AND THOUGH
MODELS SHOW SOME WEAK SUBSIDENCE AND CAPPING BETWEEN 800-700MB THE
OVERALL PATTERN SUPPORTS BROADSCALE LIFT AND BY MIDNIGHT THE
THREAT OF SEVERE WEATHER SHOULD BE ON THE INCREASE...BOTH DAMAGING
WINDS AND ISOLATED TORNADOES. WILL BE THE MOST CONCERNED ABOUT
STORMS FORMING AHEAD OF THE FRONT IN THE UNDISTURBED VERY MOIST
AIRMASS. HELICITIIES SHOULD PEAK BETWEEN 3 AM AND NOON FOR MOST
AREAS WITH THIS AS THE CORRESPONDINGLY HIGHEST THREAT. AS THE
FRONT MOVES THROUGH TUESDAY EXPECT THE WIND PROFILES TO BECOME
MORE LINEAR AND THREAT TRANSITIONS TO DAMAGING WINDS AND HEAVY
DOWNPOURS. FAST MOVING STORMS AND LINEAR NATURE OF THE CONVECTIVE
SYSTEM WILL PROBABLY LEAD TO EVERYONE GETTING 1 TO MAYBE 2 INCHES
OF RAIN WITH SOME ISOLATED 3-4 INCH AMOUNTS. WITH ALL THE CLOUD
COVER EXPECTED TEMPERATURES SHOULD STRUGGLE TO GET TO THE 74-75
DEGREE RANGE BUT IF IT GETS MUCH WARMER THAN 78 THE CAPE GETS FAR
MORE IMPRESSIVE AND SEVERE THREAT WILL PROBABLY INCREASE
DRAMATICALLY. STORMS SHOULD SWING THROUGH AND OUT OF THE EASTERN
AREAS BETWEEN 4 PM AND 8 PM...POSSIBLY SOONER. RAIN CHANCES FALL
DRASTICALLY IN THE WAKE OF THE CONVECTIVE SYSTEM WITH DRY AIR
QUICKLY FLOWING IN FROM THE WEST AND NORTHWEST. MILD AFTERNOON
TEMPERATURES ON TAP WEDNESDAY THROUGH SUNDAY. OVERNIGHT LOWS
GETTING DOWN INTO THE UPPER 40S TO UPPER 50S DURING THE SAME
PERIOD. RAIN CHANCES SHOULD RETURN NEXT MONDAY AND HAVE TRENDED
THE EXTENDED FORECAST TOWARD THE ECMWF THINKING THAT GIVEN THE
WEAKER FLOW ALOFT AND MORE ZONAL THAT ANY FRONT SETTLING THROUGH
THE PLAINS WILL WEAKEN WITH RETURN FLOW UNDERWAY SUNDAY
NIGHT/MONDAY.
45

&&

.MARINE...

ONSHORE WINDS WILL CONTINUE TO STRENGTHEN TODAY/TONIGHT (DESPITE A
BRIEF LULL THIS MORNING). HAVE EXPANDED/TWEAKED WITH THE TIMING OF
THE SMALL CRAFT CAUTION FLAGS FOR TODAY ACROSS THE COASTAL WATERS.
THEN BY LATE TONIGHT..AN UPGRADE TO A SMALL CRAFT ADVISORY FOR THE
COASTAL WATERS WITH CAUTION FLAGS OVER THE BAYS. THESE VERY STRONG
ONSHORE WINDS WILL BE HELPING TO FUEL POSSIBLE STRONG STORMS LATER
TONIGHT ACROSS NRN PARTS OF SE TX...BUT THIS ACTIVITY NOT EXPECTED
TO REACH THE BAYS/COASTAL WATERS UNTIL THE LATTER PART OF TUES. IN
THE MEAN TIME...WIDELY SCT STREAMER SHRA WILL BE POSSIBLE.

OF NOTE REGARDING TIDES...PROBLEMS ARE POSSIBLE THIS AFTERNOON AT/
AROUND HIGH TIDE. PROJECTIONS OF ELEVATED ASTRONOMICAL TIDES ALONG
WITH INCREASED WAVE RUN UP (FROM THE STRONG WINDS)...COULD LEAD TO
BRIEF PERIODS OF WATER ON ROADWAYS AROUND GALVESTON BAY. THERE MAY
BE SIMILAR ISSUES TUES MORNING WITH THAT HIGH TIDE AS WELL.

THE ASSOCIATED COLD FRONT (WITH THE UPPER LEVEL STORM SYSTEM) WILL
BRING LIGHT/MODERATE OFFSHORE WINDS TO THE MARINE AREAS TUES NIGHT
INTO WEDS. HIGH PRESSURE LINGERING OVER THE SRN PLAINS/MID MISSIS-
SIPPI VALLEY WILL HELP KEEP A MOSTLY E/NELY FLOW IN PLACE THE REST
OF THE WEEK. 41

&&

.AVIATION...

MESSY PATTERN THIS MORNING AS WAA BEGINS TO RAMP UP. HOWEVER BEFORE
IT REALLY SETS UP...IFR CIGS TO PREVAIL. ISO STREAMER SHRAS/RA WILL
ALSO BE POSSIBLE. WILL BE KEEPING WITH VCSH/VCTS WORDING FOR STORMS
LATER TODAY (WITH THE FIRST S/WV). OTHERWISE CIGS EXPECTED TO FLIRT
WITH MVFR CAT THIS AFTN. THE MORE ORGANIZED LINE OF TSRAS STILL AP-
PEARS TO BE ON TRACK FOR TUES. 41

&&


&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 77 64 66 47 71 / 60 80 100 0 0
HOUSTON (IAH) 77 70 75 51 73 / 40 50 100 20 0
GALVESTON (GLS) 77 72 75 56 73 / 20 30 90 40 0