November Weather Discussion. Rollercoaster Pattern.

[srainhoutx]

My guess, texoz is warm air advection kicked in for you folks in Central TX. We were cooler yesterday morning, but as southerly winds increased yesterday, dew point rose along with the temps. Last night we were much warmer than the night before. Stay safe in the Hill Country! SPC Update...

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1111 AM CDT MON NOV 01 2010

VALID 011630Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF EAST
TX...WESTERN AR...AND WESTERN LA...

MORNING WATER VAPOR LOOPS SHOW A RATHER IMPRESSIVE UPPER TROUGH
DIGGING/ROTATING EASTWARD ACROSS THE SOUTHERN PLAINS. A STRONG
SURFACE COLD FRONT WILL CONTINUE TO SURGE SOUTHWARD ACROSS TX/LA
THROUGH THE FORECAST PERIOD. AHEAD OF THE FRONT SOUTHERLY LOW LEVEL
WINDS HAVE TRANSPORTED RICH GULF MOISTURE BACK INTO TX/LA WITH 70 F
DEWPOINTS ALMOST AS FAR NORTH AS SHV. STEEPENING MID LEVEL LAPSE
RATES WITH TIME COMBINED WITH PARTIAL SUNSHINE WILL YIELD AFTERNOON
MLCAPE VALUES OF 1500-2500 J/KG.

MOST MODEL GUIDANCE AGREES THAT SCATTERED THUNDERSTORMS WILL PERSIST
THROUGH THE MORNING AND EARLY AFTERNOON NEAR THE TX/LA COAST. A FEW
OF THESE STORMS MAY ROTATE WITH A RISK OF HAIL AND GUSTY WINDS.
HOWEVER...THE THREAT OF ORGANIZED SEVERE STORMS APPEARS RATHER LOW
IN THIS AREA.

LATER TODAY...STORMS ARE EXPECTED TO INTENSIFY ALONG THE COLD FRONT
OVER NORTHEAST TX AND WESTERN LA. STRONGER EFFECTIVE SHEAR AND CAPE
IN THIS AREA WILL PROMOTE MORE ORGANIZED SEVERE STORMS CAPABLE OF
LARGE HAIL AND DAMAGING WINDS. THIS ACTIVITY WILL LIKELY INCREASE
IN AREAL COVERAGE THROUGH THE EVENING...BUILDING SOUTHWESTWARD ALONG
THE FRONT INTO CENTRAL TX...AND SPREADING SOUTHEASTWARD TOWARD THE
GULF COAST. DESPITE INCREASING CONVECTIVE COVERAGE...THE SEVERE
THREAT WILL LIKELY WANE BY MIDNIGHT.

..HART/ROGERS.. 11/01/2010

[srainhoutx]

HGX Aviation Update gives some hints on the arrival of the front...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1227 PM CDT MON NOV 1 2010

.AVIATION...
EXPECT CONVECTION TO PERSIST ACROSS THE SRN TIER OF SE TX COUNTIES
FOR THE NEXT COUPLE HOURS. WITH DAYTIME HEATING MAY SEE SOME
ADDITIONAL LATE AFTN DEVELOPMENT ALONG A COLUMBUS-LIVINGSTON LINE.
COLD FRONT AND UPPER TROF WILL APPROACH THIS EVENING AND EXPECT
INCREASING AREAL PRECIP COVERAGE. STEEP LAPSE RATES WILL FAVOR
SOME EMBEDDED STRONGER TSRA WITH HAIL/DOWNBURSTS BEING PRIMARY
THREAT. FRONT ITSELF SHOULD BE APPROACHING CLL TOWARD SUNSET...THE
HWY 59 CORRIDOR SHORTLY AFTER MIDNIGHT...THEN OFF THE COAST AROUND
OR SLIGHTLY BEFORE SUNRISE. EXPECT MVFR CIGS AND POST FRONTAL SHRA
TO CONTINUE FOR MOST TERMINALS INTO LATE MORNING BEFORE WE
EVENTUALLY GET DRY SLOTTED. 47

[srainhoutx]

Another very lengthy Area Forecast Discussion from HGX this afternoon. Busy night ahead folks. Stay Tuned!

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
342 PM CDT MON NOV 1 2010

.DISCUSSION...

A RETURN TO MUCH-NEEDED RAINFALL ACROSS THE COASTAL COUNTIES...WITH
RECORD-TYING MAXIMUM TEMPERATURES TO BEGIN THIS MONTH OF NOVEMBER.

EASTERN COLORADO SHORTWAVE ENERGY DIVING SOUTHWARD INTO THE BASE
OF A MEAN UPPER TROUGH DIGGING DOWN OVER WESTERN TEXAS. LOWER
LEVEL SPEED/DIRECTIONAL CONVERGENCE ALONG THE COASTLINE...IN TANDEM
WITH OLD CONVECTIVE OUTFLOW...HAVE KEPT TODAY`S PRECIPITATION CONFINED
TO A RELATIVELY NARROW SW-TO-NE COASTAL/NEARSHORE BAND. ANTICIPATING
THAT ONCE THE SURFACE COLD FRONTAL BOUNDARY (CURRENTLY DRAPED ALONG
A DFW METROPLEX TO KILLEEN TO JUNCTION ARC) BEGINS TO CROSS THE
I-35 CORRIDOR LATER THIS AFTERNOON...WEST CENTRAL TEXAS CONVECTION
WILL BEGIN RIDING UP NEAR-PARALLEL TO THE ADVANCING FRONT. THIS
WILL HAVE NORTHEASTWARD MOVING CELLS TRAVELING ACROSS OUR NORTHERN
1/3RD OF THE CWA AROUND 00Z...WITH A POSSIBLE QUASI-LINEAR SQUALL
LINE (OR BETTER ORGANIZED MCS) EVOLVING AND MARCHING SOUTHEAST
TOWARDS THE SOUTHERN HALF OF THE FA DURING THE 00-06Z TIME FRAME.
PLEASE REFER TO THE HWOHGX FOR THE SPECIFICS ON RAINFALL AMOUNTS
AND THE PRIMARILY THREATS.

COLD FROPA ACROSS CWA THROUGH 06Z WITH A COASTAL EXIT BY 14-15Z
TUESDAY MORNING. ALL INDICATIONS ARE THAT ENOUGH DRY AIR WILL WRAP
AROUND A BROAD CUT-OFF UPPER LOW AS IT MOVES DIRECTLY OVER US
TUESDAY AFTERNOON THROUGH EARLY WEDNESDAY. MUCH UNCERTAINTY ON
AREAL COVERAGE AS IT IS ALL DEPENDENT UPON THIS LOW`S EVENTUAL
SOUTHERN JOG AND GULF EXIT...BUT THE PROBABILITIES OF MANY RECEIVING
LATE TUESDAY THROUGH LATE WEDNESDAY RAINFALL REMAIN MODERATELY HIGH.
ISENTROPIC ANALYSIS HAS MOIST AND COOL N-NE AIR RIDING UP THE 305K
THETA SURFACE IN A CYCLONIC MANNER...OR AROUND THE NORTHERN PERIPHERY
OF LOW DURING LATE TUESDAY THROUGH EARLY WEDNESDAY. WHEN 305K WINDS
FAIL TO ADVECT HIGH HUMIDITY UPWARDS...THERE WILL BE ENOUGH THERMO
INSTABILITY AS TO COUNTERACT THIS LACK OF UPSLOPE WEDNESDAY. THUS...
AS THE UPPER LOW SLIDES INTO THE WESTERN GULF WEDNESDAY...THERE
SHOULD BE ENOUGH OVERALL INSTABILITY TO SUPPORT WIDELY SCATTERED
SHOWERS AND...TO A LESSER DEGREE...ELEVATED THUNDER IF THE PROG
SOUNDINGS COME TO FRUITION. A TOTALLY SATURATED COLUMN WITH MORE
EFFICIENT CAA WILL MAKE FOR A COOL AND OVERCAST BACKGROUND DAY
WITH THE OCCASIONAL FOREFRONT SHOWER. IN SUMMARY...HAVE FORECAST
OF UPPER 50S (NORTH) TO LOWER 60S FOR WEDNESDAY`S MAXIMUM TEMPERATURES.
THERE WILL BE A LAG OF A COUPLE OF DAYS UNTIL OVERNIGHT MINIMUMS
BOTTOM OUT DUE TO A SLOWER LATE WEEK RETURN TO WEAKER NORTHERLIES
AND CLEAR SKIES. PER BETTER WED-THU CAA (5-8 DEG C 85 H TEMPS)
AND A MUCH TIGHTER SYNOPTIC GRADIENT BETWEEN 1030 MB HIGH BUILDING
INTO WESTERN TEXAS IN RELATION TO THE EASTERN-EXITING SURFACE LOW
OVER CENTRAL GULF...NORTH WINDS WILL SIGNIFICANTLY STRENGTHEN TO
NEAR 15-20KT SUSTAINED INLAND TO GALE FORCE OVER THE LOCAL WATERS
WELL INTO MID-LATE THURSDAY.

THE LATER PERIOD WILL BE MORE IN-LINE WITH NOVEMBER STANDARDS AS
FLOW BECOMES A BIT MORE ZONAL OVER THE STATE. SLOW MOISTURE RETURN
WILL ALLOW FOR LESSENED DIURNAL SWINGS BY THIS TIME NEXT WEEK.
BELOW NORMAL TEMPERATURES AND PARTLY CLOUDY SKIES THIS COMING
WEEKEND...CHILLY MORNINGS IN THE AVERAGE UPPER 30S TO MIDDLE 40S
WARM INTO THE VERY COMFORTABLE AVERAGE UPPER 60S TO MIDDLE 70S.
AFTER ANOTHER DRY WEEK (THU-TUE)...A NEARING SOUTHERN PLAINS
TROUGH NEXT WEDNESDAY WILL ONCE AGAIN INCREASE RAIN CHANCES. 31

[Snowman]

when are theses showers and thunderstorms going to form north of us? and will any of those storms to our east come this way?

[srainhoutx]

Looks like a squall line will form across the Hill Country and move S and E as the evening wears on. There is some concern from HGX that a Mesoscale Convective System (MCS) will also form in the northern reaches of the forecast area after 00Z or 7-8 PM local time.

[svrwx0503]

Right now we are just waiting for initiation to occur over the next 3 hours or so along the frontal boundary. You can see a cu field developing along the front in the visible satellite image posted by srain. Latest RUC data shows plenty of instability out there with ML CAPE in the 2000-2500J/kg range across the region along with steepening low level lapse rates. Both parameters continue to support a wind/hail threat through the evening as storms develop along the front.

[srainhoutx]

Matt, it appears the hail threat has gone up some as the day has progressed. Is that true?

[Andrew]

Great set of pics to show what is expected:












Also this loop really shows the setup nicely:

http://aviationweather.gov/adds/satelli ... g&itype=wv

[svrwx0503]

Matt, it appears the hail threat has gone up some as the day has progressed. Is that true?

The latest model data and RUC surface mesoanalysis suggests a good amount of CAPE in the -10 to -30C level which is favorable for hail development...also with lowering wet-bulb-zero heights later this evening in response to the approach of the mid-level trough suggest that hail will be the primary threat, with strong winds a close second. I think SPC wanted to emphasize that threat by upping the hail probabilities in the last few outlooks.

[Andrew]

gfs:




svrwx0503 looks to be a busy one. You ready to keep your radar up for a while?

[svrwx0503]

Wind shift line showing up nicely on KGRK radar this afternoon.

[svrwx0503]

Taking a look at some RUC model soundings just north of the CLL area. It looks like there might still be somewhat of a cap around 800mb. Also, moisture seems to be lacking a bit as well. Moisture levels increase substantially and we remained un-capped down here in southeast Texas...therefore we might not see storms really start to develop until the front starts to nudge its way into our northwestern counties later this evening.

[wxman666]

I can see some convection starting to fire over the northern counties. It is looking pretty threatening here in Cypress right now. Think we'll see an MCD from the SPC soon guys?

[wxman666]

Right on the money, lol! http://www.spc.noaa.gov/products/md/md2031.html

[srainhoutx]

Right on the money, lol! http://www.spc.noaa.gov/products/md/md2031.html

Getting some thunder now in NW Harris County...

MESOSCALE DISCUSSION 2031
NWS STORM PREDICTION CENTER NORMAN OK
0624 PM CDT MON NOV 01 2010

AREAS AFFECTED...PARTS OF SOUTHEAST TEXAS

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 012324Z - 020100Z

IT IS NOT YET CERTAIN THAT A WW WILL BE NEEDED. BUT TRENDS ARE
BEING MONITORED FOR THE POSSIBILITY OF AN INCREASING SEVERE THREAT.

THE LOW-LEVEL FOCUS FOR CONVECTIVE DEVELOPMENT THIS EVENING REMAINS
A BIT UNCLEAR. BUT SCATTERED CONVECTIVE DEVELOPMENT APPEARS
UNDERWAY NEAR THE JUXTAPOSITION OF THE AXIS OF STRONGER PRE-FRONTAL
BOUNDARY LAYER HEATING AND THE AXIS OF RICHER BOUNDARY LAYER
MOISTURE RETURN /AS CHARACTERIZED BY LOWER 70S SURFACE DEW
POINTS/...NEAR THE NORTHWEST EDGE OF THE SOUTHEAST TEXAS COASTAL
PLAIN. MID-LEVEL INHIBITION HAS SUPPRESSED ACTIVITY SO FAR...BUT
STRENGTHENING MID-LEVEL FORCING WITH THE APPROACH OF THE DIGGING
UPSTREAM TROUGH...AND PERHAPS RADIATIONAL COOLING ATOP THE DEEP
SURFACE BASED MOIST LAYER...MAY WEAKEN CAPPING BETWEEN NOW AND
02-03Z.

ALTHOUGH LOW-LEVEL FLOW FIELDS AND SHEAR ARE PROGGED TO REMAIN
WEAK...STRENGTHENING OF MID-LEVEL FLOW FIELDS MAY YIELD SUFFICIENT
SHEAR FOR SUSTAINED UPDRAFT ROTATION...ENHANCING THE RISK FOR LARGE
HAIL IN STRONGEST STORMS.

..KERR.. 11/01/2010


ATTN...WFO...LCH...SHV...HGX...EWX...

[svrwx0503]

It looks like my hunch that convection won't really start developing until the boundary starts to move into our northwester counties is correct. As the SPC hinted at in their MCD, areas across the hill county and central Texas remained capped just enough to inhibit the widespread convective development which was expected by this time earlier today. As was mentioned, stronger mid-level forcing is starting to move in from the northwest which could help kick things off over the next couple of hours.

[srainhoutx]

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
645 PM CDT MON NOV 1 2010

TXZ178-179-199-020045-
MONTGOMERY-POLK-SAN JACINTO-
645 PM CDT MON NOV 1 2010

...STRONG THUNDERSTORM DEVELOPING...

AT 641 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 23 MILES SOUTHWEST OF LIVINGSTON OR 6 MILES
SOUTHWEST OF COLDSPRING...MOVING NORTHEAST AT 15 MPH.

PEA SIZE HAIL...ARE POSSIBLE WITH THIS STORM.

LOCATIONS IN THE PATH OF THIS STORM INCLUDE...LAKE
LIVINGSTON...LIVINGSTON...GOODRICH AND COLDSPRING.

[svrwx0503]

Right now a strong storm is located half way between Bellville and Sealy just east of SH36 moving ENE. Radar currently indicating 1.21'' hail possible with this storm. Another strong storm is currently located across northeast Montgomery and southwest San Jacinto counties.

[wxman666]

Power syruggling to stay on in Cypress.

[srainhoutx]

From Nesdis...

SATELLITE PRECIPITATION ESTIMATES..DATE/TIME 11/01/10 2228Z
SATELLITE ANALYSIS BRANCH/NESDIS---NPPU---TEL.301-763-8678
LATEST DATA USED: GOES-13 2215Z JANKOT
.
LOCATION...MISSISSIPPI...LOUISIANA...TEXAS...
.
ATTN WFOS...JAN...LIX...LCH...HGX...
ATTN RFCS...LMRFC...WGRFC...
.
EVENT...MOD/HEAVY RAIN IN DEEP MOISTURE
.
SATELLITE ANALYSIS AND TRENDS...BLENDED TPW PRODUCT HAS SHOWN INCREASE IN
MOISTURE THE LAST FEW HOURS OVER LA /MS WITH PWATS RUNNING 1.7-1.8". THIS
IS ESSENTIALLY RUNNING 175-200% OF NORMAL SUGGESTING PLENTY OF MOISTURE
AVAILABLE TO PRODUCE CONVECTION THIS AFTERNOON/EVENING. THE BROADER
PICTURE SHOWS A HIGHLY DIFFLUENT UPPER-LEVEL PATTERN WITH A POTENT
SHORT WAVE SEEN IN WATER VAPOR DIVING SE INVOF OF TX PANHANDLE. FURTHER
INTENSIFYING THE DIFFLUENCE IS A 70 KNOT JET MAXIMA SEEN IN EXPERIMENTAL
SATELLITE WIND PRODUCT OVER E TX NE THROUGH SE AR. IR IMAGERY SHOWS
ENHANCEMENT ALONG SW LA COAST ENE THOUGH SW MS. AT THIS TIME BEST
ENHANCEMENT IS CENTERED AROUND IBERIA COUNTY WITH CLOUD TOPS COOLING
TO -64C. MANUAL SATELLITE ESTIMATE TECHNIQUE SUGGEST RATES ARE RUNNING
.9"/30 MIN IN THE DEEPEST CORES. AUTOMATED SATELLITE ESTIMATES SHOW A
GENERAL 1-2" AMOUNTS FROM CAMERON COUNTY ENE THOUGH IBERVILLE COUNTY.
.
AN ANNOTATED SATELLITE GRAPHIC SHOWING THE HEAVY PRECIPITATION THREAT AREA
SHOULD BE AVAILABLE ON THE INTERNET ADDRESS LISTED BELOW IN APPROXIMATELY
10-15 MINUTES.
.
SHORT TERM OUTLOOK VALID 2230-130Z...MEDIUM CONFIDENCE FACTOR IN SHORT
TERM OUTLOOK...DO NOT EXPECT EXCEEDANCE OF 3 HOUR FFG AS FFG IS RUNNING
ABOVE 3.0" BUT EXPECT CONVECTION TO CONTINUE FOR THE NEXT 2-3 HOURS
WITH BEST RATES FROM VERMILION COUNTY ENE THROUGH LIVINGSTON COUNTY WITH
1-2"/HR RATES POSSIBLE IN DEEPEST CONVECTION. WILL CONTINUE TO MONITOR.