June: Onshore Flow Returns With Increasing Gulf Moisture

[srainhoutx]

PW's are high enough 'locally' to monitor. Those are rather impressive and should things develop, heavy rainfall potential could be more of an issue here rather than N TX...we'll see what future guidance offer...

HGX Afternoon Update:

THE MAIN FORECAST CHALLENGE WILL THE THREAT OF LOCALLY HEAVY
RAINFALL OVER THE LAST PART OF THE WORK WEEK. THE GFS AND ECMWF
DIFFER ON THE PRECIPITABLE WATER FORECAST WITH THE GFS BEING THE
DRIER MODEL. THE MAX PW/S DIFFER FROM AROUND 1.7 ON THE GFS TO
AROUND 2.0 INCHES ON THE ECMWF BETWEEN WEDNESDAY AND FRIDAY. THIS
RANGE IS ABOUT A QUARTER OF AN INCH BELOW THE 2 STANDARD DEVIATION
AND 99TH PERCENTILES FOR THIS TIME OF YEAR ON BOTH THE CLL AND LCH
SOUNDING RECORDS. FOR NOW WILL CONTINUE TO MENTION THE POSSIBILITY
OF LOCALLY HEAVY RAINFALL IN THE HAZARDOUS WEATHER OUTLOOK. WOULD
LIKE TO SEE THE MODEL SOLUTIONS TO COME TOGETHER BETTER BEFORE
GOING WITH HIGHER POPS THAN 40 PERCENT OR THE MENTION OF HEAVY
RAINFALL IN THE FORECAST GRIDS.

[srainhoutx]

The overnight guidance continues to advertise an unsettled pattern being Tuesday and continuing until the upcoming weekend.

The Euro/GFS are suggesting a meandering upper low across Texas with a stalled frontal boundary and little to no mid/upper flow pattern to move the disturbance or front for much of the next 7 days. Texas will be trapped between a blocking pattern to our E with a developing trough across the W with little to no winds, Add to the mix a surge of deep tropical moisture with pw's in the 1.7 - 2.0 range which is well above normal and the boundary draped across the region for 4-7 days acting as a focal point for daily showers/storms.

With little in the way of movement and daytime sea breeze activity firing off showers/storms, the threat of heavy rainfall could become an issue should the pattern linger. Daily rainfall totals could approach 1/2 - 3/4 of an inch or higher in stronger storms. There still remains some concern that a very slow moving surface low could form along Coastal Texas adding to the available moisture and instability later this week.

06042012 06Z Tropical Formation Probs gexyrfpr.png (11.45 KiB) Viewed 4246 times

[srainhoutx]

HPC QPF Discussion for Texas:

THE TAIL END OF THE VORTICITY NEAR NERN OK SHOULD
GRADUALLY SINK THROUGHOUT THE DAY INTO NRN TX/SRN OK AND BEGIN TO
TEAM-UP WITH THE UPPER DYNAMICS NEAR WEST TX FOR POSSIBLE AXIS OF
HEAVIER CONVECTIVE RAINFALL BUT NONE OF THE MODELS HAVE MUCH OF
CLUE HERE EITHER. HPC GENERALLY FOLLOWED THE ECMWF HERE BUT QPF
AMOUNTS COULD VERY WELL BE ON THE CONSERVATIVE SIDE DUE TO THE
VERY LIGHT 850MB WINDS/STEERING CURRENT.

[srainhoutx]

Morning e-mail from Jeff:

Dry period of late looks to be ended this week as a pattern change aloft takes place.



Upper level high pressure which has been anchored over the region for several weeks will break down starting late today while a plume of deep tropical moisture currently located over the western Caribbean Sea and SE Gulf of Mexico moves northwest and inland along the TX coast tonight/Tuesday. An upper level low currently located in NE MX will move NNE into central TX on Tuesday as the ridging aloft breaks down into a mid level height field weakness over TX. The weakening ridge aloft combined with the transport of a tropical air mass into the region would in itself support a decent chance of rainfall along the seabreeze each afternoon…and this should begin on Tuesday.



Tropical air mass becomes entangled into the upper level low which will be located over NC TX by Wednesday and this feature appears to gradually become somewhat warm core “tropical” given the abundance of tropical moisture in a weak upper level wind field. With PWS climbing to near 2 standard deviations above normal across central and northern TX and near the 99th percentile across SE TX (PWS of 1.75-2.0 inches by late week) concern is grown that this feature will begin to affect much like a warm core tropical system with excessive rainfall focused near the center during the overnight hours. Extremely weak wind fields will make for slow storm motions and with a tropical air column overhead, expect some really hefty rainfall totals for the end of the week. For now with the main upper/mid level system remaining west of our region, suspect any of the really big flooding rainfall may be just W/NW of our region, but SE TX will lie in the favorable inflow region off the Gulf. This system is looking similar to the warm core lows of the summer of 2007 which produced devastating flooding rainfall across portions of NC TX. Will take a closer look on Tuesday and start to determine possible rainfall amounts for the middle to end of the week.



Wet pattern looks to linger on into the weekend and even into next week with the weakness in the sub-tropical ridge remaining over the area. This will allow daily chances for thunderstorms along the seabreeze front.

[MontgomeryCoWx]

I remember the Summer of 2007 very well. It was my first Summer in Houston and I was in a Softball league. We had games on Thursday and we were rained out for 5 straight weeks due to standing water and rain.

That was a fun Summer through Winter as we saw some fun weather.

[srainhoutx]

While we remain capped today, the 12Z GFS is trending toward the Euro suggesting the TUTT low near Del Rio will meander ENE then stall across Central Texas and a slow moving/stalled frontal boundary will remain across the region from Wednesday into the coming weekend. PW's have increased to the 1.7 range now in the Houston Metro and just offshore, pw's range from 2.1 to nearly 2.5 suggesting a very deep tropical airmass is heading inland.

[srainhoutx]

The 12Z Canadian continued the wet scenario and the HPC did recognize the potential in their Model Diagnostic Update. We'll see if the Euro continues the trend for a wet pattern for the next 5-7 days...

UPPER LOW OVER TEXAS...
PREFERENCE: 12Z GFS/12Z CANADIAN/00Z ECMWF COMPROMISE WITH
AVERAGE CONFIDENCE

BY LATE WEDNESDAY...THE 12Z UKMET/12Z NAM ARE THE WEAKEST WHILE
THE GFS/CANADIAN/ECMWF SHOW GOOD AGREEMENT. ON FRIDAY...THE GFS
WAS THE ONLY PIECE OF DETERMINISTIC GUIDANCE WHICH ADVERTISED THIS
FEATURE...SO IT HAS MAINTAINED THE BEST MULTI-DAY CONTINUITY HERE.
THE SYSTEM IS IN A TRICKY AREA OF THE FLOW PATTERN THROUGH
TUESDAY...NEAR A COL BETWEEN TROUGHING ACROSS THE WEST AND
EAST...BEFORE A 700 HPA LOW MAY OR MAY NOT FORM TO ITS SOUTH WHICH
WOULD ACT TO OPEN IT UP AND RETROGRADE IT INTO NORTHERN MEXICO.
THE PREFERENCE IS FOR A 00Z ECMWF/12Z GFS/12Z CANADIAN COMPROMISE
HERE WITH CONFIDENCE NO GREATER THAN AVERAGE CONSIDERING ITS
PRECARIOUS POSITION WITHIN THE GENERAL FLOW PATTERN.

[Portastorm]

Encouraging words from EWX this afternoon:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
303 PM CDT MON JUN 4 2012

.DISCUSSION...
12Z MODEL RUNS LOOKING DECISIVELY WETTER FOR THE REMAINDER OF THE
WEEK. APPEARS THE UPPER LOW/WEAKNESS OVER NE MEXICO WILL LIFT SLOWLY
ENEWD TONIGHT AND TUESDAY AND BRING ISOLATED TO SLIGHT CHANCES FOR
CONVECTION ALONG THE RIO GRANDE THIS EVENING...AND ACROSS MUCH OF
THE CWA TUESDAY AFTERNOON INTO TUESDAY EVENING. MEANWHILE MODELS
ARE FAIRLY CONSISTENT IN DEVELOPING AN UPPER LOW(POSSIBLY FROM AN
MCV) OVER NW TX...AND DROPPING THE LOW SLOWLY SWD INTO S CENTRAL
TX BY THE LATE WEEK. AN ASSOCIATED WEAK SURFACE BOUNDARY WILL
ACCOMPANY THE LOW WITH A BRIEF E-NELY WIND SHIFT BY THU AFTERNOON.
THIS SLOW MOVING UPPER LOW WILL GENERATE SCATTERED AFTERNOON/EVENING
CONVECTION WITH LOCALLY HEAVY DOWNPOURS WED THRU AT LEAST FRI OR
EVEN SAT. COOLER AFTERNOON TEMPERATURES AS WELL AND WITH TEMPS
LIKELY NOT CLIMBING OUT OF THE 80S ALL BUT THE WEST AND SW.

WITH THE UPPER LOW CENTERED IN THE NRN/NERN CWA BY THU EVENING...COULD
SEE NOCTURNAL CONVECTION DEVELOP NEAR/UNDER THE UPPER LOW/FRONTAL
BOUNDARY IN THE OVERNIGHT HOURS. THERE WILL BE A POTENTIAL FOR
HEAVY RAINFALL WITH THIS PATTERN AND MODELS ALREADY BEGINNING TO
GENERATE SOME SIGNIFICANT RAINFALL AMOUNTS. WILL UPDATE THE HWO TO
REFLECT POTENTIAL FOR HEAVY QPF POTENTIAL FOR THE THU NIGHT INTO
FRIDAY NIGHT. THE UPPER LOW DRIFTS EASTWARD LATE SATURDAY INTO
SUNDAY WITH A RIDGE BUILDING IN FROM THE WEST. THEREFORE DECREASING
POPS FROM THE WEST SUNDAY WITH WARMER TEMPS RETURNING.

[srainhoutx]

The latest HPC QPF Update is suggesting that Central Texas will be the 'bull eye' in the 1-3 day range as the upper low (TUTT) meanders across that area acting as a focal point for heavy showers/storms. The Euro has also trended a bit wetter for E/SE TX as the stalled frontal boundary lies across our region and the upper air trough/low drifts very slowly SSE toward the Middle Texas Coast. Should that occur, SE TX would be in a favorable setup for heavier rainfall later this week. In fact the Euro suggests the boundary will slowly lift out late this weekend with abundant tropical moisture in place. There is also an issue of a Kelvin wave approaching from the W that tends to increase convective potential late week into the weekend. My hunch is we will begin to see the NWS ramp up the heavy rainfall threat by tomorrow morning if the model trends continue. We will see.

[srainhoutx]

Nice discussion from Corpus this afternoon...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CORPUS CHRISTI TX
322 PM CDT MON JUN 4 2012

.SHORT TERM (TONIGHT THROUGH TUESDAY NIGHT)...A STRENGTHENING LOW
LEVEL JET WILL CONTINUE TO POOL IN MOISTURE ACROSS THE AREA...
ESPECIALLY ALONG THE RIO GRANDE. THE UPPER LEVEL LOW ADVERTISED
THROUGH PREVIOUS AFDS STILL LINGERS ALOFT...STRETCHED ACROSS
NORTHEAST MEXICO AND WESTERN TEXAS. THE NORTHEASTERLY FLOW ALOFT
WILL CONTINUE TO ALLOW FOR THUNDERSTORM ACTIVITY OFF OF THE SIERRA
MADRE WITH CURRENT AFTERNOON RADAR OBSERVATIONS SHOWING ONGOING
CONVECTION. WITH AREAS OF INCREASED MOISTURE CONVERGENCE AND
DECENT LAPSE RATES FARTHER EAST THAN PREVIOUS DAYS...ALONG WITH
CAPE VALUES PROGGED OVER 2000 J/KG...CONVECTION SHOULD CONTINUE TO
DEVELOP CLOSER WITH A BETTER CHANCE TO AFFECT THE FAR WESTERN
BRUSH COUNTRY. SHEARING IS LACKING...SO AM THINKING THAT MOST
THUNDERSTORM ACTIVITY SHOULD REMAIN BELOW SEVERE CRITERIA...
HOWEVER AN ISOLATED THUNDERSTORM OR TWO MAY BRIEFLY DEVELOP BEFORE
THE LOSS OF DAYTIME HEATING. OVERNIGHT...MOISTURE VALUES INCREASE
OVER THE CENTRAL TEXAS COASTAL WATERS WITH PWATS AROUND 1.5 OR
GREATER. DECENT 0-1KM LAPSE RATES OVER THE WATERS COMBINED WITH
LITTLE TO NO CIN WILL LEAD TO STREAMER SHOWER ACTIVITY...WITH
SHOWERS SLOWLY MOVING INLAND AS THE MORNING PROGRESSES. MENTIONED
THUNDER BY THE LATE MORNING DUE TO HEATING COMBINED WITH THE
POSITIONING OF THE UPPER LOW OVER THE AREA. THUNDERSTORMS REMAIN A
POSSIBILITY IN THE AFTERNOON ALONG THE SEABREEZE. CONCERNS FOLLOW
WITH THUNDER ACTIVITY DEVELOPING FARTHER NORTH OF THE CWA LATE IN
THE AFTERNOON/EVENING MOVING SOUTHWARD. CURRENTLY...BEST DIFFLUENT
FLOW ALOFT TO SUSTAIN CONVECTION REMAINS WELL NORTH OF THE AREA.
HOWEVER...IF STORMS DO MOVE FAR SOUTH ENOUGH TO INTERACT WITH THE
MOISTURE CONVERGENCE ALONG THE SEABREEZE...THUNDERSTORMS MAY
APPROACH THE NORTHWESTERN CWA. AS FOR NOW...THINKING TIMING MAY BE
OFF SO WILL KEEP ONLY SILENT POPS FOR THE NORTHERN AREAS...WITH
CONTINUED MENTION OF THUNDER FOR FAR WESTERN WEBB FOR STORMS
MOVING OUT OF MEXICO. THERE WILL BE ANOTHER ROUND OF STREAMER
SHOWERS FOR TUESDAY NIGHT. AS FOR TEMPERATURES...WILL CONTINUE TO
REMAIN ON THE WARM SIDE OF GUIDANCE.

&&

.LONG TERM (WEDNESDAY THROUGH MONDAY)...MODELS ARE TRENDING WETTER
IN THE EXTENDED FORECAST...ESPECIALLY THURSDAY THROUGH SATURDAY
ACROSS SOUTH TEXAS. THE GFS/ECMWF/CANADIAN AND ENSEMBLE MEMBERS ARE
IN RELATIVE GOOD AGREEMENT OF AN UPPER LEVEL LOW DEVELOPING ACROSS
NORTHWEST TEXAS TUESDAY INTO WEDNESDAY...BENEATH THE CENTRAL CONUS
RIDGE. THE UPPER LEVEL RIDGE BUILDS ACROSS FAR WEST TEXAS AND NEW
MEXICO...SUCH THAT THE UPPER LEVEL LOW SLOWLY DRIFTS SOUTHEAST
AROUND THE PERIPHERY OF THE RIDGE...EVENTUALLY MOVING OVER
SOUTH-CENTRAL AND SOUTH TEXAS DURING THE FRIDAY AND SATURDAY TIME
FRAME. AHEAD OF THE SYSTEM SFC-700MB FLOW WEAKENS AND TURNS EAST
WITH SIGNIFICANT COOLING IN THE 850-700MB LAYER. GRADUAL MOISTENING
TAKES PLACE...WITH PWATS REACHING 135% OF NORMAL BY FRIDAY. WITH
WEAKNESS ALOFT DRIFTING TOWARDS THE REGION THIS SPELLS BETTER
CHANCES FOR SCATTERED TYPE PRECIPITATION ACROSS MUCH OF SOUTH TEXAS
BEGINNING POSSIBLY AS EARLY AS THURSDAY...BUT MORE SO FRIDAY INTO
SATURDAY. THE UPPER LEVEL LOW IS FORECAST TO SLOWLY KICK NORTHEAST
TOWARDS LOUISIANA SUNDAY INTO MONDAY...WITH A GRADUAL DECREASE IN
POP CHANCES THEN EXPECTED ACROSS SOUTH TEXAS. HAVE RAISED POPS
THURSDAY THROUGH SATURDAY INTO THE CHANCE/SCATTERED CATEGORY ACROSS
MUCH OF THE AREA. QPF AMOUNTS LIKELY TO HIGHEST DURING THE
FRIDAY-SATURDAY TIME PERIODS. THE 12Z CANADIAN IS MOST BULLISH
SHOWING MUCH OF THE AREA GETTING 2 TO 4 INCHES. 12Z GFS AND ECMWF
INDICATING BETWEEN 1/2 TO 2 INCHES. SHOULD MODEL TRENDS CONTINUE...
POPS MAY LIKELY GO MUCH HIGHER IN FUTURE FORECASTS. TEMPS...SHOWED
GRADUAL DECREASING TREND IN HIGHS THU-SAT...THEN WARMING AGAIN
SUN-MON.

[srainhoutx]

Big storms are firing across NW Texas and along the Rio Grande this evening. We should start to see things begin to destabilize tomorrow as the ridge shift a bit E and the sea breeze develops tomorrow afternoon. Eyes will then turn to Central Texas as the upper air disturbance enhances showers/storms across the Lone Star State as well as the frontal boundary sagging SW across NEW Texas...

[rnmm]

What kind of weather are we potentially looking at here? Will these be severe storms or just big rain makers? Just wanting to know what to expect.

[Ptarmigan]

Could this mean a wet June like in 2004 or July 2007? I remember they were wet due to slow moving upper level low pressure systems.

[Andrew]

I think a warm core system is a possibility and current radar already shows storms firing south of the area representing the already noticeable increase in moisture. Also looking out west Storms have really been firing tonight. 00z GFS and CMC came in a little wetter but the two big questions for this situation is will this turn into a warm core system and where does it "stall" and meander around. The closer it is to SE Texas the more rain we will get. Last thing noticeable is that models have been showing a lot of thunderstorm activity in the gulf we might see some type of low possibility develop but those chances seem low (just something to keep an eye on).

http://radar.weather.gov/Conus/southplains_loop.php

[srainhoutx]

This morning there are active storms over N Central TX from the MCS that slowly moved E from the Lubbock Area last night. Left over boundaries should be the focal point for showers/storms today and better chances may extend into Central Texas this afternoon as well as the Dallas/Ft Worth Metroplex.

Streamer showers are developing along the Middle TX Coast on down to Corpus as deep tropical moisture heads inland. A slow meander upper trough/low will be the trigger for heavy rainfall the next several days. A weak frontal boundary will slowly sag SW from NE TX on Thursday and linger across the area from most of the weekend. My hunch is daily scattered showers/storms will fire with 1/2 to 3/4 inch amounts and isolated 1-2 inch amounts (mainly N & W) with stronger storms. I believe there is some potential for 3-4 inch amounts locally for the period, but it will all depend on meso features that can not be determined with much confidence and model guidance making for a complex and complicated forecast.

One year ago we saw high temps of 105F and a severe drought and on this date in 2001, Tropical Storm Allison made landfall dropping 8+ inches of rain at IAH. We will not see a repeat of either of those records today...

[srainhoutx]

HPC is suggesting a transition to a warm core low is possible...

QUANTITATIVE PRECIPITATION FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
553 AM EDT TUE JUN 05 2012


FINAL DAY 1...DAY 2 AND DAY 3 QPF DISCUSSION
VALID JUN 05/1200 UTC THRU JUN 08/1200 UTC
REFERENCE AWIPS GRAPHICS UNDER...PRECIP ACCUM - 24HR


DAY 1...

06Z UPDATE... NO SIGNIFICANT CHANGES FROM PREVIOUS ISSUANCE BASED
ON THE 00Z EC... 03Z SREF MEAN AND 06Z NAM.

...SOUTHEAST/GULF COAST STATES...

THE COMBINATION OF A WELL DEFINED MID-LEVEL VORT NEAR CENTRAL MS
EARLY THIS MORNING AND A FRONTAL BOUNDARY NEAR THE TN VLY INTO THE
SRN APPALACHIANS SHOULD IGNITE ANOTHER ROUND OF POSSIBLE ORGANIZED
HEAVY RAINFALL FROM THE SOUTHEAST COAST WESTWARD TO THE
ERN/CENTRAL GULF COAST. THE VORT MAX SHOULD SLIDE DOWNSTREAM TODAY
FROM CENTRAL MS TO THE PANHANDLE OF FL OR NRN FL... WHILE THE
AMPLIFIED UPPER TROUGH OVER THE NERN QUAD OF THE COUNTRY HELPS
LOWER HEIGHTS AND STEER THE COLD FRONT SOUTH AND EAST INTO THE
SOUTHEAST/SOUTH. THE MODEL GUIDANCE APPEARS TO HAVE A DECENT
HANDLING OF THE SURFACE BOUNDARY PROGRESSION BUT IS NOT HANDLING
THE SMALL SCALE MCS VERY WELL THIS MORNING. NEEDLESS TO SAY...
ENOUGH LIFT AND INSTABILITY AHEAD OF BOTH FEATURES WITH AOA 1.75
INCH PWS SHOULD BE SUFFICIENT FOR POSSIBLE HEAVY RAINFALL FROM
SERN LA TO COASTAL GA/SC. HPC GENERALLY FOLLOWED A BLEND OF THE
OPERATIONAL ECMWF WITH THE SREF MEAN AND INTERNAL PSEUDO BIAS
CORRECTED GUIDANCE FOR POSSIBLE 1 TO 3 INCH AMOUNTS.

...TX...

A SHEAR AXIS PRESENT ACROSS THE TX PANHANDLE/WEST TX WITH AOA 1.5
INCH PWS IS FUELING ORGANIZED CONVECTIVE HEAVY RAINFALL AND THIS
MID-LEVEL FEATURE APPEARS TO EITHER BECOMING BETTER ORGANIZED OVER
THE NEXT 24 HRS OR THE MODEL GUIDANCE IS SLOW IN CAPTURING THE
FEATURE BASICALLY TRAPPED UNDER THE PLAINS RIDGE. THUS THE
MID-LEVEL VORT/LOW SHOULD NOT MOVE MUCH OVER THE NEXT 24 HRS... AS
850MB WINDS ARE GENERALLY 5-10 KTS OR LESS. HPC GENERALLY FOLLOWED
A COMBO OF THE ECMWF AND GFS WITH THIS SMALL SCALE FEATURE AND
TRENDED MORE CLOSELY TOWARD THE GFS ON HEAVIER QPF AMOUNTS...
DESPITE THE GFS DEPICTING POSSIBLE CONVECTIVE FEEDBACK BULLS-EYE.
HPC GENERALLY WENT WITH A SIMILAR AXIS FROM SERN CO/TX PANHANDLE
SEWRD INTO CENTRAL TX FOR ANOTHER DIURNAL SURGE OF INSTABILITY
WITH THE DEEPER MOISTURE FOR HEAVY RAINFALL THIS AFTN PERSISTING
INTO THE OVERNIGHT HRS... WITH 1 TO 3 INCH AMOUNTS.

...NW/NRN ROCKIES...

A DEEP AND ANOMALOUS UPR TROUGH WILL SWEEP UP THROUGH THE NWRN
QUAD OF THE COUNTRY ON TUES... WHILE GOING NEG TILT. A SHORT WAVE
IMPULSE IS ALREADY LIFTING THROUGH THE INTERIOR NW EARLY THIS
MORNING... WITH ANOTHER POTENT JET STREAK ROUNDING THE BASE OF THE
UPPER TROUGH LIFTING FROM NRN CA TO WRN MT. THIS SHOULD EXIT THE
INITIAL HEAVY RAIN/PRECIP SHIELD OUT OF THE INTERIOR NW/NRN
ROCKIES INTO WRN CANADA BEFORE ANOTHER PRECIP MAX TAKES FORM ON
THE BACKSIDE OF A PROGGED SURFACE LOW AND NEAR AN INVERTED SURFACE
TROUGH OVER NWRN MT. THE RESULTANT SHOULD BE ORGANIZED MDT TO HVY
RAINFALL FROM CENTRAL ID/WRN MT NORTH INTO CANADA... AS MOIST
SERLY FLOW CONTINUES. HPC GENERALLY FOLLOWED A BLEND OF THE
OPERATIONAL GFS AND ECMWF FOR QPF AMOUNTS.


DAYS 2 AND 3...

...SOUTHEAST U.S./FLORIDA...

ONE AREA TO WATCH FOR POTENTIALLY HEAVY RAIN IN THE DY2-3
PERIOD...IS NORTHERN FLORIDA AND PERHAPS FAR SOUTHERN GEORGIA. A
PLUME OF HIGH-PW AIR WILL WORK ITS WAY UP FROM THE CENTRAL
GULF...AND BECOME CAUGHT IN THE WESTERLIES. THIS AIR MASS SHOULD
PROMOTE ISOLATED TO SCATTERED VERY HEAVY DOWNPOURS. BROAD SCALE
ORGANIZATION...HOWEVER...IS MORE QUESTIONABLE. THOUGH THERE WILL
BE BROAD LOW LEVEL CONVERGENCE...THE BULK OF THE MID AND UPPER
LEVEL FORCING - ASSOCIATED WITH A RESIDENT LONGWAVE TROUGH AND
ENTRANCE REGION OF AN ASSOCIATED JET STREAK - WILL REMAIN NEAR AND
JUST EAST OF THE COASTLINE. MEANWHILE...DEEP CONVECTION WITHIN THE
HIGH-PW PLUME OVER THE GULF...MAY TEND TO PROPAGATE SOUTH AND
WESTWARD INTO THE MOISTURE AXIS...PLACING A SECOND PRECIP MAXIMUM
OFF THE WEST COAST OF FLORIDA. ACTIVITY OVER
LAND...THEREFORE...MAY BE LARGELY DRIVEN BY DIURNAL EFFECTS.
THUS...WHILE THERE WILL BE POTENTIAL FOR VERY HEAVY LOCAL
DOWNPOURS...THERE IS NOT YET ENOUGH OF A LARGE SCALE SIGNAL TO
DRAW AN EXCESSIVE RAIN THREAT.

...TEXAS...

TEXAS WILL BE A SECOND AREA OF STRONG INTEREST. HERE A MID LEVEL
TROUGH WAS PINCHING OFF FROM THE FLOW...AND BECOMING TRAPPED
BENEATH A SHORTWAVE RIDGE DEVELOPING IN THE CENTRAL PLAINS STATES.
DIURNAL BUILD UP AND RELEASE OF INSTABILITY/LATENT HEATING...SUCH
AS WAS TAKING PLACE THIS MORNING IN WEST TEXAS...WILL SUSTAIN THE
MID LEVEL LOW THROUGH DAY 3. FLORIDA STATE PHASE SPACE PLOTS SHOW
SOME TENDENCY FOR THIS SYSTEM TO DEVELOP A WARM CORE WITH
TIME...WHICH AT A QUICK GLANCE...DOES SHOW UP IN THE GFS...WITH
WARMING AT 700-500 MB. THE 00Z ECMWF IS GOOD ON THE LARGE
SCALE...BUT IS PERHAPS OVER-FORECASTING THE WARM CORE CHARACTER OF
THIS SYSTEM...AS THAT MODEL KEEPS A CONCENTRATED AREA OF HEAVY
RAIN TIED DIRECTLY TO THE MID LEVEL LOW THROUGH THE FULL 24 HOURS
OF THE DAY 3 PERIOD. THIS RESULTS IN WHAT IS PROBABLY AN
UNREALISTIC 9-INCH PLUS QPF TOTAL OVER NORTH TEXAS. SINCE THE
LOCATION AND ORIGIN OF THIS FEATURE FAVORS AT LEAST MODEST COLD
POOL GENERATION...WE PREFERRED SOLUTIONS SUCH AS THE NAM AND 00Z
GFS...WHICH PROGRESS THEIR QPF SIGNAL SLOWLY SOUTH AND EAST WITH
TIME.

[srainhoutx]

Morning e-mail from Jeff:

A slow moving upper level low will combine with deep tropical moisture to produce an extended period of wet weather across much of the state.



Water vapor shows an upper level low over S TX and another upper level low starting to form over NW TX (the old remains of an meso scale vorticity center from an overnight thunderstorm complex over the TX panhandle). While over the Gulf of Mexico deep tropical moisture is advancing NW off the Yucatan toward the TX coast this morning. GOES sounder shows a large area of PW values of 1.8-2.2 inches across much of the central and western Gulf of Mexico moving toward the coast and this is confirmed by the increase in scattered showers/thunderstorms off the coast this morning. This moisture will make its way inland today and continue to increase with PW values reaching 1.9-2.2 inches by Thursday into the weekend. Additionally, a weak frontal boundary will approach the area from the north/northeast Wednesday and stall across our northeastern counties helping to add another ingredient for rainfall. The NW TX upper level system will combine with the southern TX upper low and form a broad upper level low/trough over the state which becomes trapped on the southern side of a large central US ridge in a blocking pattern. The result will be little motion or a slow drift of the upper level system.



With tropical moisture becoming increasingly entrained into the upper level system there is the possibility that the system will take on warm core features the most important the ability of the system to focus deep convection near its center in the overnight hours…similar to a tropical cyclone as it moves inland. Such systems in the past have produced incredible amounts of rainfall (usually in a small isolated area near or just east of the center). We will need to keep a close eye on this over the next 2-4 days as the upper level system meanders over central TX and then begins a slow eastward drift across SE TX this weekend.



Combination of all the above mentioned factors will lead to high rain chances starting Wednesday and continuing into early next week. Once temperatures achieve the mid to upper 80’s by late morning expect thunderstorms to begin to develop in our very moist air mass. Very weak wind fields will promote slow storm motions of less than 10mph pointing strongly toward a heavy rainfall threat…especially later in the week when the deeper tropical moisture arrives. With grounds dry from the past few weeks and the expected scattered nature of the rainfall at least through Thursday…do not think flooding will be a concern for the next 48 hours. From Friday onward as grounds saturate more run-off will be generated with additional rainfall and flooding could become a concern. We should have a good idea by Thursday if this system will behave somewhat like a tropical system and if that is the case rainfall amounts will need to be raised significantly.



For now will go with widespread 2-4 inches of rainfall through the weekend across the region, and would not be surprised if a few location pick up more than that.



Note: Today, last year, Houston reached 105 degrees a record for that date and the entire month of June…the start of our incredible summer heat wave. The City would go on to record 46 days at or above 100 shattering the old record of 32 in 1980. Additionally we were in severe drought conditions: For example last year Hobby Airport had only recorded 5.4 inches of rainfall compared to 26.29 inches this year.

[ticka1]

Is a warm-core low tropical in nature? Just curious.

[srainhoutx]

Is a warm-core low tropical in nature? Just curious.

It looks to be a transition from a combination of cold core lows (one over NW TX and the other S of Del Rio which is more of a TUTT (tropical upper tropospheric trough )) with time as the deep tropical moisture from the Gulf warms the 700mb/850mb levels in about 36 hour or so. I will add that models will have a very difficult time pin pointing were the heaviest rainfall will develop and if we see that full transition to warm core, night time very heavy rainfall could be possible around the northern and eastern half (semi circle) of that feature much like a tropical system would generate over land. Past examples would be 2007 (non tropical warm cored low) as well as TS Hermine 2010. The interesting thing is to see the guidance slowly sag that mid level disturbance SE in time from Central Texas to a position off the Middle Texas Coast this weekend. We will see.

[Portastorm]

I've been following the weather for most of my 49-plus years and I don't know if I can recall seeing a cold-core upper low transition to a warm-core system over LAND. Sure we see it in the tropics and over water although it is still not all that common. But to see this happen over land? Crazy stuff, man! This should be a fun weather week if for no other reason the "gee whiz" factor for us geeks!

Hope we in south central Texas and you good folk in southeast Texas see healthy rainfall!