Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Brownsville Texas
617 am CDT Mon Oct 24 2016
Discussion...updated for latest aviation discussion below.
Aviation...multi-layered clouds to provide scattered-broken VFR conditions
through the day with decreasing cloudiness west to east later
today and tonight. Light and variable winds this morning becoming
generally light southeast this afternoon.
Previous discussion... /issued 406 am CDT Mon Oct 24 2016/
Short term (today through tuesday): back to the autumn weather
doldrums. The relatively cool and drier air has retreated and the
typical muggy deep south Texas weather regime has returned. The
advertised shortwave trough is crossing Texas as we write without
much fanfare in our County Warning Area outside of some multi-layered clouds.
Moisture values and depth remain depleted especially in that mid
layer between 850-600mb keeping the chance of rain near or below
10 percent. Model guidance continues to show very low pops so
confidence remains rather high that no accumulated precipitation
will develop today. The mid level shortwave trough weakens as it
lifts northeast tonight and gets absorbed into the general
westerly anticyclonic flow Tuesday leaving all of Texas under a
broad mid level ridge. The dry mid layer deepens but moisture in
the near surface layer increases as the influx of Gulf moisture in
response to a broad easterly flow continues. No substantial lift
provide by a weak seabreeze and with subsidence provided by the
building mid level ridge keeping US under a partly to occasionally
mostly cloudy sky with no rain anticipated. As for temperatures
the broad mid levels ridge and increasing dew points will maintain
near to slightly above normal highs, upper 80s to lower 90s and
lows mid 60s to lower 70s.
Long term (tuesday night through monday):
At the beginning of the long term, broad 500 mb ridging will run from
west to east in a zonal pattern. A short wave trough signature will
be over the High Plains, moving east. Surface high pressure will
extend over the north Gulf from the north.
A weak east to east southeast wind will prevail on Wednesday, and
sea breezes will be possible then and each afternoon through Friday.
A weak surface trough axis will be marked by showers moving up the
west Gulf shoreline along northeast Mexico. Through the end of the
week, mid level ridging over north Mexico and the southwest border
states will also influence the local area, providing stability
aloft, leaving open only the Gulf for the introduction of any rain
chances, which will remain slight.
Late in the week, the GFS seems to develop a western Caribbean low,
which will help tighten the gradient over the East Gulf. Other than
that, and the potential for more swell moving toward the cwa, the
effects of the feature for the County Warning Area appear to remain minimal during
the forecast period. The European model (ecmwf) is less solid with the development of
any low, but does carry a weak surface circulation nonetheless.
In summary, upstream ridging will block any serious weather threat
from the west, while activity over the Gulf will be more inclined to
show up on the doorstep as Gulf based shower or diurnal sea breeze
activity. Without a strong focusing mechanism or lift rainfall, if
any, will remain fairly light. Temperatures will be around five to
ten degrees warmer than normal.
today through Tuesday...broad surface high pressure extends
across the entire Gulf waters with weak low pressure over West
Texas. This will maintain a light to moderate southeast wind and a
low sea. Latest buoy data suggest the long period swell has
temporarily relaxed with mainly a local wind wave to impact the
coastal waters through Tuesday.
Tuesday night through Friday...broad ridging will extend across
the Gulf, but at the surface high pressure will weaken slightly,
yielding to lower pressure both upstream and over the southwest
Gulf. Light to moderate east winds will prevail across much of the
Gulf, with low to moderate seas which will include a significant
swell component. Swell may add another foot to wave heights by
Thursday and Friday as the persistent east winds continue across
the Gulf, with exercise caution conditions for seas possible going
into the weekend. Despite stabilizing ridging aloft, low level
instability over the southern Gulf will be enough to support
shower and thunderstorm generation, and isolated nearshore and
coastal convection will be possible at times.
Preliminary point temps/pops...
Bayview/Port Isabel 87 73 86 71 / 0 10 10 10
Brownsville 88 71 89 70 / 0 10 10 10
Harlingen 89 71 90 68 / 0 10 10 10
McAllen 91 70 93 68 / 10 10 10 10
Rio Grande City 88 67 89 67 / 0 10 10 0
South Padre Island 82 76 84 74 / 0 10 10 20
This product is also available on the web at: