Area Forecast Discussion
Issued by NWS Brownsville, TX

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764
FXUS64 KBRO 210914
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
414 AM CDT Mon Aug 21 2017

.SHORT TERM (Today through Tuesday):Water vapor satellite imagery
shows the center of 500 mb low pressure spinning over the central
Gulf of Mexico south of the Mississippi River delta and north of the
Yucatan Peninsula. During the short term forecast period, model
guidance progs this system to steadily advance west into the western
Gulf of Mexico. Deeper tropical moisture, combined with the 500 mb
low weakening the long-standing 500 mb high pressure ridge, will
result in isolated showers and thunderstorms for the immediate three
coastal counties of the BRO CWFA as well as all Lower Texas coastal
waters. With only isolated convection forecast for the region,
temperatures should have no difficulty reaching above normal
levels.


.LONG TERM (Tuesday Night through Sunday):Long term is beginning
to look interesting as Global, Hurricane and ensembles model
forecast tracks are are well clustered with the future path of the
remnants of former TC Harvey. Last nights 00Z and 06Z Invest 09L
track guidance shows a consistent path of a potential tropical
cyclone moving into Northern Tamaulipas State or South Texas in
96-120 hours. The Main question and the large uncertainty factor
is the future development of this disturbance. Currently the
tropical wave and remnant broad circulation shows, currently over
the Central Caribbean, shows no signs of organization. Even with a
medium chance (50 percent)of tropical Cyclone development in the
next two days, this disturbance still needs to cross the Yucatan
which will disrupt any short term organization that takes place.
However, conditions become more favorable for development as the
system emerges into the Southern Gulf with all models indicating
some type of TC Wednesday. Once the system moves into The
consistent northwest track shown by all the latest
models/ensembles is due to the westward movement of the upper
level low currently over the Central Gulf of Mexico. The upper low
works its way into the Western Gulf Tuesday and weakens into the
trough Wednesday. This leaves a weakness between the ridge over
West Texas and a developing ridge over the Northeast Gulf. This is
provide the "window of opportunity" for any potential Tropical
Cyclone to turn right or northwest.

Forecast remains unchanged in the Tuesday and Wednesday time frame
with only a mention of sea breeze activity,mainly in the eastern
counties, as some increase in moisture is indicated with the
approach of the upper low. Then forecast trends upward with pops
Thursday through the weekend into the 30-50 percent range with
Friday and Saturday likely the best days for rainfall with the
surge of tropical moisture and/or any potential Tropical Cyclone.
For Sunday and Monday models suggest any remnants moving northwest
along the Rio Grande with an upper level trough moving into
Central Texas keeping at least some chance of rain into early next
week.

Temperatures continue to be hot and above normal Tue-Wed with some
potential slight cooling if the rain and increased cloud cover
materialize. Model guidance is focusing on Friday as the coolest
day of the week. We can only hope and continue to monitor future
develops.

&&

.MARINE:(Today through Tuesday): Buoy 42020 reported southeast winds
around 10 knots gusting to around 12 knots with seas slightly over
2.5 feet with a period of 5 seconds at 03 CDT/08 UTC. Surface high
pressure over the western Gulf of Mexico will produce light to
moderate winds and low to moderate seas for the Lower Texas coastal
waters through the period.

Tuesday night through Friday...Weak surface high pressure over the
Western Gulf to maintain a light to occasional moderate onshore
flow along with a slight sea. Forecast becomes more uncertain with
the potential re-intensification of the remnants of former
tropical cyclone Harvey over the southern Gulf Wednesday with a
potential northwest track towards northern Tamaulipas waters
Thursday and Friday. Wind and Sea Forecast are very conservative
at this time with the plenty of uncertainty on any disturbance or
developing TC. It is prudent for all marine interests along the
Lower Texas coast to monitor future forecast for any potential
tropical development in the GOM.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  95  78  95  78 /  20  20  20  10
BROWNSVILLE          96  77  96  77 /  20  20  20  10
HARLINGEN            98  75  98  76 /  20  20  20  10
MCALLEN             101  78 101  78 /   0   0   0  10
RIO GRANDE CITY     102  77 102  77 /   0   0   0  10
SOUTH PADRE ISLAND   92  81  90  82 /  20  20  20  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

This product is also available on the web at:
HTTP://WEATHER.GOV/RGV

66...short term
59...long term
56...graphics/PSU



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