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Area forecast discussion 
National Weather Service Houston/Galveston Texas
612 am CDT Thursday Aug 28 2014


See aviation.



Scattered showers and thunderstorms are just inland from the coast this morning.
Expect activity to gradually progress further inland today for a
prolonged period of scattered activity. Best chance for thunderstorms at iah and
northward will be in the after hours. Expect scattered activity to
dissipate with the loss of heating early this evening. 33


Previous discussion... /issued 430 am CDT Thursday Aug 28 2014/

surface analysis this morning shows low pressure off the Lower Texas
coast with a sheared and weak upper level low per latest water
vapor imagery. Surface trough extends NE along the Texas Gulf Coast and
a focus for scattered showers and thunderstorms. Some of this activity
has moved inland along the Upper Texas coast. The activity seems to
be running into drier air farther inland. Highest moisture content
seems to be just along the coast looking at GOES sounder precipitation
water imagery. With that in mind...kept 40/50 probability of precipitation in the forecast
for today along the coast with probability of precipitation decreasing rapidly farther
inland. Mesoscale models WRF-arw/Texas tech WRF and rapid refresh all
continue trends of convection developing later today inland with
day time heating and as higher moisture slowly pushes inland. This
seems to be in line with current forecast update. As will be the
case the next couple of days...stronger storms will be monitored
for locally heavy rainfall. Rain rates of 1-2 inches an hour with
not be out of the question.

Thunderstorm chances will continue through the weekend with a
growing concern of heavy rainfall Friday into Saturday. Water
vapor imagery shows an area of thunderstorms in the southern Gulf
north of the Yucatan that is supported by high tropical moisture
per GOES sounder data. GFS/NAM/ECMWF seem have resolved this
fairly well and forecast this moisture to reach the Upper Texas
coast late Friday into Sat. During this time an upper level trough
now in The Rockies will move across the plains with the trough
axis pushing through Texas. The NAM at least also still resolves
some vorticity from the upper low now over Lower Texas coast and
brings that feature northward over southeast Texas late Friday into Sat. The
GFS and European model (ecmwf) show similar features but weaker. Last few runs of
the NAM have really hit southeast Texas hard with high quantitative precipitation forecast amounts
suggesting the possibility of heavy rainfall and flooding. The
GFS/European model (ecmwf) keep most of the moisture and heavy rainfall farther
east into SW la. The forecast will keep 50/60 probability of precipitation but concerned
that higher rain chances may be needed if the NAM continues its
trend and gains support from the GFS/European model (ecmwf) solutions.

Rain chances do taper off sun through Tuesday as higher moisture
moves out of the area and the trough axis lifts northeast. There
is another short wave trough moving across the North Plains sun into
Monday with weakly amplified upper level flow. This should allow for
a fairly flat upper level ridge to develop Tuesday/Wednesday next week with
the pattern becoming more zonal. The forecast keeps some 20 probability of precipitation
in the forecast for any convection that develops with day time
heating but any thunderstorm activity should be fairly isolated at this
point with subsidence from the ridge. Precipitation water values drop to
around 1.7-1.9 or just enough to support a storm or two.

GFS/Canadian and European model (ecmwf) also bring a tropical wave into the S Gulf
and Bay of Campeche by Tuesday. There may be some tropical
organization to the system for the middle of next week. The system
has been consistently forecast to move into the Mexico coast but
could still allow for moisture to track northwards into Texas. European model (ecmwf)
keeps the system as an open wave while GFS/Canadian are stronger.
At this point there should not be any impact to the Texas coast even
if the system becomes a tropical cyclone. NHC gives this system a
20 percent chance of tropical development once reaching the northwest



Moderate southeast winds will continue today across the southeast Texas
coastal waters north of a weak low pressure area that will move
inland late today across south Texas. Scattered showers and
thunderstorms will continue the next several days as well as tide
levels around 1 foot above normal. Will have a caution statement
for the offshore zones through middle-day with 15-20 knots winds and 5
to 6 foot seas...expect winds to relax some this after...but likely
increase again tonight. 33


Preliminary point temps/pops...
College Station (cll) 95 75 94 75 91 / 30 20 50 30 40
Houston (iah) 92 75 91 75 88 / 40 30 50 40 60
Galveston (gls) 88 81 89 80 86 / 50 30 50 60 60


Hgx watches/warnings/advisories...
GM...small craft should exercise caution until 2 PM CDT this
afternoon for the following zones: waters from Freeport to
the Matagorda Ship Channel 20 nm to 60 nm...waters from
High Island to Freeport 20 to 60 nm.




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