Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
454 am AST Tuesday Jul 22 2014
Synopsis...surface high pressure across the central Atlantic will
continue to maintain moderate to fresh trade wind flow across the
local area next several days. Tropical Depression Two is forecast
to weaken next 48 hours. Remnants of this low pressure system will
approach the local area Friday.
Discussion...scattered showers were noted overnight over the
local coastal waters...with some affecting Puerto Rico. These
showers were moving quickly westward. Therefore...rainfall
accumulation was not significant. Latest satelite images showed
patches of low level moisture embedded in the trade wind flow
approaching the local area from the east. Scattered showers are
expected to continue to affect the local islands this morning into
the afternoon hours. Once again...available moisture...will
combine with local effects to produce scattered showers with
isolated thunderstorm this afternoon...mainly over the western
interior and northwest sections of Puerto Rico.
The main weather feature this morning is Tropical Depression Two
which was located around 1400 miles southeast of Puerto Rico. This
system will encounter unfavorable atmospheric conditions next
couple of days as it moves west northwest. Therefore...the
official forecast from the National Hurricane Center indicates this
system will weaken next 48 hours and is forecast to become a
trough of low pressure by the time it reaches the Lesser
For our area...still expected a significant increase in moisture
associated with this system...as passes near or over the local area
by Friday. Latest 22/00z GFS computer model run showed
precipitable water above 2.0 inches over the local area with deep
tropical moisture affecting the local area through Saturday.
Therefore...an increase in shower and thunderstorm activity can be
expected both days as the remnants of this system move across the
region. Stay tuned for latest information on Tropical Depression
Aviation...scattered rain showers mainly offshore this morning and again tonite as
moisture deepens below 10 kft...but MVFR will be brief/isolated at
tjsj/tist/tisx/tncm/tkpk. Scattered rain showers/isolated thunderstorms and rain west PR this after and
again Wednesday after WI local MVFR and obscured mountains wind below fl150 east-southeast 12-24
knots becoming east late Tuesday night.
Marine...seas up to 5 feet and winds up to 19 knots are expected
to prevail across the coastal waters today. Small craft should
exercise caution across most coastal waters.
Preliminary point temps/pops...
sju 88 79 92 79 / 40 20 20 10
stt 89 79 91 81 / 50 30 30 20