Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Brownsville Texas
414 am CDT Monday Sep 15 2014
Short term /now through Tuesday/...middle level high pressure is
draped across the northern Gulf and with upper level low on the west
side of the Yucatan and upper level high over northern Mexico...
northeasterly middle/upper level winds persist with a shear line
across south Texas stretching across the northeast Gulf.
Stationary boundary persists across the Gulf waters nudging just
south of Brownsville. This...along with increasing moisture /GOES
precipitable water/ across the western Gulf associated with
westward moving tropical wave across the western Gulf is
contributing to showers and thunderstorms across our coastal waters at this time.
Not much headway has been made into the coastal counties but
believe next batch may make it into Willacy/Cameron counties in
the predawn hours and have raised probability of precipitation in the coastal waters and
southern valley areas.
Kept previous package mostly in tact. Tropical wave will continue
westward with west side affecting more of the area today as time
GOES on with the apex of the wave crossing the coast Tuesday morning
and across the middle/Upper Valley Tuesday afternoon. Precipitable waters prognosticated to
be 2.1-2.3 through the period with slightly lower precipitable waters entering the
southern coastal waters by late Tuesday as the wave moves further
inland and weakens. The best chance for showers and thunderstorms
today and tonight will be Highway 281 eastward where scattered coverage
will be located and more isolated coverage west of this line. As the
wave moves inland Tuesday scattered to locally numerous showers and
thunderstorms expected across most of the area. Did raise probability of precipitation
Tuesday to likely as this time looks optimal due to low/middle
convergence...maximized moisture...and weak upper diffluence.
Consensus models approve the boost in probability of precipitation for Tuesday.
Will see a few breaks in the clouds today so highs will make it into
the upper 80s to the lower 90s /mainly west/ today. With expected
coverage of precipitation and clouds elected on the cooler side of
guidance for highs Tuesday.
Long term /Tuesday night through Sunday/...residual low pressure
troughing along the northeast Mexican coast will keep lingering
showers over the area Tuesday night. Meanwhile...a cold front will
stretch across the north Gulf Coast...courtesy of high pressure over
the Midwest. A 589 dam height center over south Texas and northeast
Mexico will try to get the Upper Hand on Wednesday...but too much
moisture will be at the lower levels to completely cut off rain
chances. As the tail end of a front in the vicinity gets nudged back
north...pop chances will trend down a bit Wednesday night into Thursday.
Few big changes the latter half of the week. Strong high pressure
will continue to push out of the southeast United States...focusing
convergence along an old frontal boundary in the Gulf. That will be
the origin of increasing showers and thunderstorms approaching the
Lower Texas coast Saturday and Sunday. Next weekend as well...a
tropical wave will cross the Yucatan Peninsula...likely increasing
local rain chances early next week...just beyond the current period.
Average temperatures are edging slowly down just a bit...just a degree or
two...as September progresses...and forecast values will tend to follow
suit...but will still run a few degrees above normal. Cloud cover will
weigh in on the partly cloudy or more side most of the week...with
light to moderate southeast winds determined primarily by the
synoptic pattern...until next weekend when an incoming batch of
moisture and convection shifts winds more to the east. Maintained
much of the inherited forecast with only a few small updates.
now through Tuesday...a tropical wave will impact the coastal
waters this period with scattered to locally numerous showers and
thunderstorms. Moderate winds and seas will rule this period with
seas taking a slow fall to around 3 feet by Tuesday afternoon.
Tuesday night through Friday...middle level ridging over the northwest
Gulf will not completely stymie unsettled weather across the area
during the second half of the week...and a lingering surface trough
will continue to hug the northeast Mexican coast...resulting in
persistent shower and thunderstorm activity for the Lower Texas coast. Light
to moderate southeast winds and low to moderate seas will otherwise
prevail through the period...with no advisories expected.
Preliminary point temps/pops...
Bayview/Port Isabel 88 78 88 78 / 50 50 70 40
Brownsville 88 76 88 77 / 50 50 70 40
Harlingen 89 76 90 76 / 50 50 70 40
McAllen 90 76 90 76 / 40 30 70 40
Rio Grande City 90 76 90 76 / 30 20 60 40
South Padre Island 86 79 85 79 / 50 50 70 40
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