109 
fxus64 kbro 051953 
afdbro 


Area forecast discussion 
National Weather Service Brownsville Texas 
245 PM CDT Sat Jul 5 2008 


Discussion...the mesoscale convective system that has been firing away along the Mexican 
coastline today has begun to weaken some with the current infrared satellite 
imagery showing less organization and warmer cloud tops in the most 
recent imagery. Convective surges on the north side on this area are 
moving north pretty quickly across the bro County Warning Area which is limiting the 
heavy rainfall potential somewhat. However...the high precipitable waters  holding in 
place over the region will continue to provide plenty of fuel for 
torrential rains across the region. The broad 500 mb low/trough is 
expected to linger over northeast Mexico in the short term with 
pockets of positive vorticity advection periodically ejecting out over deep south Texas over the 
next couple of days. Short range guidance from the models show 
different scenarios on the eventually movement of this trough axis 
with the GFS moving the feature in a more westerly direction later 
this week with the European model (ecmwf) moving the feature out in a more northwest 
direction. This movement will eventually hinge on the timing of the 
development of the 500 mb ridging over the Gulf Coast region which 
is expected to begin drying out the atms over the region later this 
week. The NAM has not initialized well on the current environment 
and appears to be drying out the region too quickly on Monday. So am 
going with a GFS/European model (ecmwf) solution maintaining high probability of precipitation in the short 
term...with a gradual drop of in the conv chances later this upcoming 
week. The overall quantitative precipitation forecast amounts will be tricky considering the timing 
differences showing up among the models. However...the 5 day quantitative precipitation forecast 
from HPC looks reasonable with a 3 to 4 inch bullseye located over 
and just south of the bro County Warning Area through 12z Thursday. With ever passage 
of each new area of conv...the ffg is slowly falling as the ground 
becomes more saturated. Am not yet ready to issue a Flash Flood 
Watch considering the fast movement of this rainfall and the 
periodic breaks in the conv. However...this situation will be 
closely monitored over the next several days for possible watches. 
As for forecast temperatures...since am more confident of the GFS probability of precipitation 
versus the NAM probability of precipitation...will be going below both for sun and Monday 
considering the higher confidence of the expected increased cloud 
cover and probability of precipitation. In the extended range period...the European model (ecmwf) and the GFS 
are both fairly consistent in building the 500 mb ridge over the 
Gulf Coast region further west which eventually shifts the deeper 
tropical moisture away from the region. The GFS mex MOS numbers 
respond accordingly showing a return of warmer temperatures and lower probability of precipitation 
during the latter half of this coming week. Run to run consistency 
with the GFS mex MOS looks OK and will not deviate too much from 
this trend. 
&& 


Aviation...large area of rain to the south will continue to move 
north northwest through the next 24 hours. MVFR conditions this 
afternoon and overnight lowering to IFR in and near convection. 
Expect brief breaks in rain activity overnight and Sunday...somewhat 
more so than today. 
&& 


Marine...large area of convection to the south continues to push 
into our area and showers and thunderstorms expected to continue 
along the coast and out over the coastal waters. Areas of 
stratiform rain persistent between waves of showers. Movement of 
upper level trough and surface inverted trough will push convection 
slowly westward late Sunday and Monday and should see improvement 
over marine areas by late Monday. Waves slightly higher today and 
Sunday as longer period swell approaches the beaches...generally in 
the 3 to 5 foot range. Waves higher to the south where short fetch 
from convection in the Bay of Campeche impacts more directly causing 
seas northern Mexico to bump up to 6 feet Sunday and Sunday night. 


Increasing swell and winds later in the week will bump waves in the 
offshore waters to 7 feet briefly. In the longer term berthas 
forecast track not expected to come close enough to Florida to send 
a swell across the Gulf but merits monitoring. 
&& 


Preliminary point temps/pops... 
Bayview/Port Isabel 77 83 78 84 / 100 70 40 70 
Brownsville 75 83 77 84 / 100 70 40 70 
Harlingen 74 83 76 84 / 100 70 40 70 
McAllen 74 84 76 84 / 100 70 40 70 
Rio Grande City 73 85 74 88 / 60 50 40 50 
South Padre Island 78 83 80 84 / 100 70 40 70 


&& 


Bro watches/warnings/advisories...none. 
&& 


$$ 


This product is also available on the web at: 
http://www.Weather.Gov/Brownsville 


Short term forecast graphics are also available at: 
http://www.Weather.Gov/Brownsville/fxc/fxc.Htm 


Synoptic/grids...60 
marine/aviation...51 
meso/fxc...Martinez