August 2017: Looking Back at Harvey 5 Year Later

[Rip76]

It looks like a relatively quiet day ahead for SE Texas with some mid level capping I place that likely will inhibit thunderstorm development. There is a possibility that areas to our SW along Matagorda, Jackson and Wharton Counties my have a better chance for some storms to fire off later today.

Looks like it may be our area today. (SE Texas/Houston)

Looking out at these towers building, I just sat and thought about 2009-2013(ish), where we didn't see many storms at all.
It was so strange.

[mckinne63]

We had a brief shower late morning here in Stafford. Skies are looking very cloudy and gloomy. It looks like it is missing a good chance to rain!

[Texaspirate11]

NHC will be initiating advisories by 5 PM EDT on Potential Tropical Cyclone Seven, located over the northwestern Caribbean Sea.

[srainhoutx]

Getting our second thunderstorm of the day in NW Harris County.

The National Hurricane Center will begin issuing Advisories for TD 7 at 5:00 PM EDT.

[srainhoutx]

Potential Tropical Cyclone Seven Discussion Number 1
NWS National Hurricane Center Miami FL AL072017
500 PM EDT Sun Aug 06 2017

Surface and scatterometer data indicate that the broad area of
low pressure over the northwestern Caribbean Sea still lacks a
well-defined center of circulation. However, this system is
likely to become a tropical storm before reaching the coast of the
Yucatan Peninsula late tomorrow, and advisories are being initiated
to enable the issuance of a tropical storm warning and watch for
Yucatan and Belize respectively. The scatterometer pass and NOAA
data buoy observations indicate that the maximum winds are near
30 kt. The disturbance has been experiencing westerly vertical
shear due to a nearby upper-level low and this has been inhibiting
development. Global model predictions show that this low will soon
dissipate and an upper-level anticyclone will become established
over the area. Therefore, strengthening is likely with the main
impediment being interaction with land. The official intensity
forecast is a little above the model consensus. It should be
noted that the system could become a hurricane between 72 and 96
hours, i.e. prior to reaching the Gulf coast of Mexico.

Since the center lacks definition, the initial location and motion
are quite uncertain, and my best guess for the current motion is
290/10. The steering pattern for the disturbance/tropical cyclone
is expected to be fairly straightforward and persistent for the
next few days. A general west-northwestward track is expected to
continue until landfall in mainland Mexico. The official track
forecast is generally a blend of the latest GFS and ECMWF solutions.

FORECAST POSITIONS AND MAX WINDS

INIT 06/2100Z 15.6N 82.0W 30 KT 35 MPH...POTENTIAL TROP CYCLONE
12H 07/0600Z 16.6N 83.6W 35 KT 40 MPH...TROPICAL CYCLONE
24H 07/1800Z 18.0N 85.9W 45 KT 50 MPH
36H 08/0600Z 19.0N 88.0W 45 KT 50 MPH...INLAND
48H 08/1800Z 19.9N 90.1W 35 KT 40 MPH...INLAND
72H 09/1800Z 21.0N 93.8W 60 KT 70 MPH...OVER WATER
96H 10/1800Z 21.2N 97.8W 60 KT 70 MPH...INLAND
120H 11/1800Z...DISSIPATED

$$
Forecaster Pasch

[srainhoutx]

Sunday evening briefing from Jeff:


Looking at the upper air pattern across TX this afternoon…one could wonder if it is October or August.

An upper level trough across the central US has resulted in another rare summer cold front dropping into TX. The front currently extends from SE OK to SE NM with numerous thunderstorms having formed along the boundary this afternoon over N/NC/ and WC TX. Pretty rare to see such rainfall over the heart of TX in early August and the WPC forecast of widespread soaking rainfall tonight-Tuesday over a large part of the state. Locally the air mass has been very moist today and a weak short wave moving up the TX coast resulted in a couple of rounds of thunderstorms mainly along and SE of US 59. Actually have a weak low level jet in place over the state feeding into the frontal boundary to our NW which is helping to supply a rich feed of Gulf moisture.

Global and meso scale models are in fairly good agreement with the thunderstorms currently over NC TX gradually growing upscale into a slow southward moving MCS tonight which will be approaching our N/NW counties toward sunrise on Monday. Given the numerous activity to our NW, another short wave approaching, and NW flow aloft to help move the activity southward all appear favorable for this complex to reach SE TX Monday morning. Air mass will continue to be very moist with low level feed off the Gulf keeping PWS of 2.1-2.3 inches into Tuesday. Meso and high resolution guidance shows the complex weakening as it enters SE TX Monday morning, but a southward moving outflow boundary will likely continue southward helping to set off additional storms by mid to late morning. Will keep with the thinking of the heaviest rainfall and most organized activity N of HWY 105 where 1-3 inches widespread will be possible (rare for August without a tropical system). South of HWY 105 totals could still certainly reach 1-3 inches, but the activity may be more isolated and scattered than widespread.

Actual front will sag into the area late Monday and Tuesday. This could keep activity going well into the evening hours on Monday depending on exactly how the morning activity evolves. Think the boundary will only help to destabilize the air mass and add a surface focus on Tuesday which looks to be another wet day.

Rainfall amounts over the next 48 hours could approach 3-5 inches over the area with isolated higher amounts. Storm motions should be 10-15kts, but cell training could help pile totals and that coupled with deep moisture will likely result in hourly rainfall rates of 2-3 inches under the strongest cells. Street flooding will likely be the main threat, although WPC has placed those locations north of HWY 105 in a slight risk for flash flooding late tonight and Monday.

Upper level ridge will begin to build over the area Wednesday helping to keep PTC #7 (likely TS Franklin by then) south of the TX coast. This should also help to reduce rain chances back toward climo with 30% afternoon storms along the seabreeze. Appears moisture associated with the Bay of Campeche tropical system (possibly near hurricane intensity by Wednesday) will contract around the center and remain well south of our area.

Upper ridging appears unable to gain a good foothold…so after a few “hot” and “dry” days Thursday-Saturday another weakness develops in the ridge over TX and Gulf moisture comes surging back into the region by next Sunday with rain chances once again increasing.

48hr Forecasted Rainfall Amounts:

[brooksgarner]

Brooks here:

wg8dlm5-1.GIF

Waiting for Franklin to form... No threat to Houston, according to every computer model I can conjure, thanks to the steering currents around that subtropical ridge centered over the Bahamas.

potential_7.png

See you at 10pm on KHOU...

[brooksgarner]

Capture.JPG

Good evening guys... I'm tracking the chance for morning rain/storms tomorrow, if a thunderstorm complex south of Dallas survives its trip 190 miles southeast... HRRR says yes.

5987d13a64f72685453794.gif

[Texaspirate11]

HGX NWS DISCO TONIGHT

Despite the buzz on social media, sharknado threat for Southeast
Texas will be nil tonight.

[srainhoutx]

MESOSCALE PRECIPITATION DISCUSSION 0640 NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 223 AM EDT MON AUG 07 2017 AREAS AFFECTED...CENTRAL TX CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE VALID 070622Z - 071222Z SUMMARY...SHOWERS AND THUNDERSTORMS ARE EXPANDING IN COVERAGE ACROSS CENTRAL TX. HOURLY RAIN TOTALS UP TO 2.5" AND LOCAL AMOUNTS TO 5" ARE POSSIBLE. DISCUSSION...A WEST-NORTHWEST/EAST- SOUTHEAST ORIENTED BAND OF THUNDERSTORMS IS TRYING TO FORM ACROSS CENTRAL TX, MOVING EAST-SOUTHEAST AT ~15 KTS, WHICH HAS SHOWN SOME BROADENING IN THE COLD CLOUD TOPS ON NON-OPERATIONAL GOES-16 INFRARED IMAGERY. THIS IS OCCURRING NORTH OF WHAT HAS BEEN A PROGRESSIVE OUTFLOW BOUNDARY WHICH IS LOCATED SOUTH OF SAN ANGELO. INFLOW AT 850 HPA IS INCREASING IN THIS AREA, NOW UP TO 20 KTS PER THE DEL RIO TX VAD WIND PROFILE. EFFECTIVE BULK SHEAR IS ~20 KTS. PRECIPITABLE WATER VALUES OF 1.6-2.1" EXIST IN THIS AREA PER GPS VALUES. RAP GUIDANCE SHOWS A SLOWING OF THE SOUTHWARD MOVEMENT OF THE OUTFLOW BOUNDARY AS THE INFLOW AT 850 HPA INCREASES TOWARDS 35 KTS AND BEGINS TO VEER. AS IT MOVES INTO SOUTHEAST TX, THE RAINFALL/ THUNDERSTORM BAND COULD BROADEN AS IT ENCOUNTERS 79F DEWPOINTS NORTHWEST OF HOUSTON TX. FORWARD PROPAGATION VECTORS SUGGEST THAT THE BOUNDARY SHOULD TRY TO PROGRESS SOUTH-SOUTHEAST AT 10-15 KTS, WHICH SHOULD LIMIT OVERALL TOTALS. SOME BACKBUILDING AND EASTWARD PROGRESSION IS EXPECTED WITH TIME. THE GUIDANCE THAT APPEARS TO BE CAPTURING THIS ACTIVITY THE BEST RIGHT NOW IS THE 00Z WRF NSSL, WHICH SHOWS LOCAL MAXIMA OF 5-6", WHICH COULD BE A TOUCH HIGH. HOURLY RAIN TOTALS UP TO 2.5" ARE POSSIBLE WHERE CELLS TRAIN OR MERGE ALONG WITH LOCAL MAXIMA AROUND 5" OVER THE NEXT SEVERAL HOURS, WHICH COULD EXCEED THE HIGH FLASH FLOOD GUIDANCE VALUES IN THE REGION. ROTH ATTN...WFO...EWX...FWD...HGX...SJT...

[srainhoutx]

Monday morning briefing from Jeff:

Large scale heavy rainfall event underway across much of central TX this morning.

Overnight rainfall has been excessive over portions of central TX with 4-6 inches since midnight NW of Austin around Llano, TX resulting in flash flooding. An LCRA gage at the Llano River at Llano recorded 6.03 inches since midnight. Decaying thunderstorm complex has moved deep into SE TX this morning…currently approaching the I-45 corridor N of I-10. This complex of storms has generated a well defined cold pool at the surface which is working its way SE across the area. Another, much more intense, band of thunderstorms is moving SE across the I-35 corridor and will be nearing our W/NW counties later this morning. Rainfall has already averaged 1-2 inches NW of a line from Columbus to Huntsville and an additional inch will be possible over this are in the next hour. Since this outflow along the leading edge of the cold pool has pushed well ahead of the main rain of rainfall weakening of this complex is likely over the next few hours before surface heating across the central and southern portions of the area leads to new development by mid to late morning.

As seen overnight in C TX, the main threat continues to be with slow moving or training cells which will be very capable of producing 2-3 inches of rainfall in an hour.

Slow moving short wave and front will remain overhead tonight into Tuesday with additional rounds of showers and thunderstorms likely. Heavy rainfall will continue to be the main threat with favorable moist low level feed off the Gulf and a nearly saturated air mass. Additional rainfall totals of 2-4 inches will be possible with isolated amounts upwards of 5 inches.

[srainhoutx]

Tropical Storm Franklin strengthening with sustained winds of 50 MPH. Early morning first Visible Imagery suggests there main be some rapid intensification possible before reaching the Yucatan Peninsula.

[srainhoutx]

For our Neighbors in S Central Texas...

MESOSCALE PRECIPITATION DISCUSSION 0642
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
735 AM EDT MON AUG 07 2017

AREAS AFFECTED...SOUTH CENTRAL TX

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 071135Z - 071435Z

SUMMARY...MERGER OF COMPLEXES POSE VERY HIGH BURST OF RAINFALL
WITH CONTINUED SHOWERS POSING FLASH FLOODING RISK

DISCUSSION...EXPERIMENTAL GOES-16 10.3 IR SHOWS AN EXPLOSIVE
DEVELOPMENT OF GROWING COMPLEX OF VERY COLD CLOUD TOPS (AS LOW AS
-84C) THUNDERSTORMS OVER BANDARA AND MEDINA COUNTY OVER THE LAST
HOUR OR SO. THIS IS IN RESPONSE TO INCREASED CONVERGENCE ALONG A
MID-LEVEL BOUNDARY/EFFECTIVE COLD FRONT MCV/SHORTWAVE LOCATED IN
THE THE SOUTHERN TX HILL COUNTRY WHERE LOW LEVEL FLOW HAD BACKED
IN RESPONSE TO ITS DEEPENING.

ADDITIONALLY...COLD POOL DRIVEN SQUALL LINE FROM CENTRAL TX
CONTINUES TO DRIVE SOUTH ON SOUTHERLY INFLOW...WITH THE WESTERN
EDGE OF THE LINE STALLING UNDER WEAKER FORWARD PROPAGTION (DUE TO
INFLUENCE OF SHORTWAVE TO ITS NORTHWEST) AND CURRENTLY
INTERSECTING/MERGING WITH THE NEW RAPID DEVELOPMENT.

STRONG MOISTURE FLUX AND AMPLE DEEP MOIST PROFILES SUPPORT TPWS
AOA 2.25" AND LIKELY TO SUPPORT RATES UP TO 3"/HR GIVEN THE
MERGERS. THIS MERGER/INTERSECTION SHOULD EXHAUST THE LOCAL
INSTABILITY AND SUPPORT FURTHER SOUTHERN PROPAGATION OVER THE NEXT
TWO HOURS...BUT WITH THE INCREASE IN LATENT HEAT RELEASE...FURTHER
FOCUSING/DEVELOPMENT OF AN MCV/MESO LOW WILL ALLOW FOR MODERATE TO
HEAVY RAIN SHOWERS TO REMAIN IN THE VICINTIY WITH RATES UP TO
1"/HR FURTHER COMPOUNDING ANY FLOODING CONDITIONS. AS SUCH
LOCALIZED TOTALS TO 2-3" ARE LIKELY WITH POSSIBLE 4 OR 5" HIGHLY
LOCALIZED MAXIMA POSSIBLE.

OF GREATER CONCERN...IS ANY EASTWARD SHIFT OF THE MID-LEVEL
EFFECTIVE COLD FRONT OF THE DEVELOPING MCV (WHICH GIVEN TRENDS
APPEARS LIKELY) WILL POSE A THREAT TO METRO SAN ANTONIO INCREASING
THE LIKELIHOOD FOR FLASH FLOODING CONDTIONS KNOWNING TO THE PRONE
AREA/URBAN SETTING. AS SUCH FLASH FLOODING IS CONSIDERED LIKELY.

GALLINA

ATTN...WFO...CRP...EWX...

[DoctorMu]

Yes, that's an impressive meso west of her over Austin - San Antonio. A couple of bands/outflows are swinging east towards College Station and Houston. About 1/2 inch about 4 am last night IMBY

[brooksgarner]

FYI --> My blog based on this WPC outlook -->
http://www.khou.com/news/local/flooding ... /462535009


SUMMARY...VERY HEAVY SHOWERS AND THUNDERSTORMS MOVING THROUGH

SOUTHEAST TX AND PARTS OF SOUTHWEST LA WITH INTENSE RAINFALL RATES

OF UP TO 2.5 INCHES/HR. SOME FLASH FLOODING IS POSSIBLE.



DISCUSSION...THE LATEST RADAR IMAGERY SHOWS A BAND OF VERY HEAVY

SHOWERS AND THUNDERSTORMS MOVING ACROSS THE SOUTHEAST TX COASTAL

PLAIN WHICH WILL BE IMPACTING THE HOUSTON METROPOLITAN AREA OVER

THE NEXT COUPLE OF HOURS. THE ACTIVITY IS FOCUSING IN A VERY

MOIST/TROPICAL AIRMASS AND WITHIN A STRONG INSTABILITY GRADIENT

ALONG THE IMMEDIATE MIDDLE/UPPER TX COASTLINE.



OVER THE NEXT FEW HOURS...EXPECT VERY INTENSE RAINFALL RATES WITH

CONVECTION LIKELY BECOMING A BIT FURTHER ORGANIZED OUT AHEAD OF A

WEAK AREA OF LOW PRESSURE AND AN ASSOCIATED MCV OVER SOUTH-CENTRAL

TX. THE CONVECTION WILL LIFT NORTHEAST ACROSS SOUTHEAST TX AND

GRADUALLY GET INTO SOUTHWEST LA. THE RAINFALL RATES MAY REACH 2.5

INCHES/HR GIVEN PWATS OF 2.2 TO 2.4 INCHES WHICH WILL YIELD HIGHLY

EFFICIENT RAINFALL PROCESSES.



THE LATEST SATELLITE AND RADAR TRENDS SUPPORT AS MUCH AS MUCH AS 3

TO 5 INCHES OF RAIN LOCALLY THROUGH 22Z...AND CONSIDERING THE

URBANIZED ENVIRONMENT AND SUCH HEAVY RAINFALL RATES...FLASH

FLOODING WILL BE A CONCERN GOING THROUGH THE AFTERNOON HOURS.



ORRISON

[Ounce]

What is used to ascertain if the sky is too worked over to rain, this afternoon? Thanks.

[srainhoutx]

Tropical Storm Franklin Discussion Number 5
NWS National Hurricane Center Miami FL AL072017
400 PM CDT Mon Aug 07 2017

Visible satellite imagery continues to show a fairly well-organized
tropical cyclone, although infrared images indicate some warming of
the convective cloud tops. Observations from an Air Force Hurricane
Hunter aircraft show that the storm has a fairly broad inner core,
which is consistent with the ragged eye-like feature noted on the
visible imagery. The current intensity is kept at 50 kt based on a
blend of SFMR and flight-level observations from the aircraft along
with sampling considerations. Franklin has a well-defined,
symmetric upper-level outflow pattern, and some strengthening is
still expected prior to landfall. Although the cyclone could be near
hurricane strength at landfall on the east coast of the Yucatan
peninsula, the broad inner core of the system would argue against
rapid intensification during the next 12 hours. Weakening will occur
due to the passage over the Yucatan peninsula, and restrengthening
over the very warm waters of the Bay of Campeche is forecast.
Although northerly shear could inhibit strengthening somewhat,
Franklin is predicted to become a hurricane before making
landfall in mainland Mexico. The official intensity forecast is
similar to the latest HFIP Corrected Consensus forecast.

Based on center fixes from the aircraft along with geostationary
and microwave imagery, the initial motion is northwestward or
310/11 kt. The track forecast reasoning remains basically
unchanged. A mid-level high pressure area near the northwestern
Gulf of Mexico coast should force Franklin to take a
west-northwestward to westward course for the next several days.


FORECAST POSITIONS AND MAX WINDS

INIT 07/2100Z 18.6N 85.9W 50 KT 60 MPH
12H 08/0600Z 19.1N 87.6W 60 KT 70 MPH...INLAND
24H 08/1800Z 19.9N 89.9W 40 KT 45 MPH...INLAND
36H 09/0600Z 20.3N 91.9W 50 KT 60 MPH...OVER WATER
48H 09/1800Z 20.5N 94.0W 65 KT 75 MPH...OVER WATER
72H 10/1800Z 20.5N 98.5W 55 KT 65 MPH...INLAND
96H 11/1800Z...DISSIPATED

$$
Forecaster Pasch

[jasons2k]

I'm tracking the shortwave/meso low to our northwest near Hearne, to see if new convection will get going around it and to its SE flank tonight. I think some folks will get some heavy rain overnight, so it's something that should be monitored.

[TexasBreeze]

Looks like showers popping around the remnant vortex currently around College/Bryan area...

[srainhoutx]

I emptied .70 of an inch from Friday until Sunday evening last night. Emptied another 1.82 from the gauge tonight. My yard is happy.