Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service San Juan PR
724 PM AST Sat Oct 25 2014
Synopsis...upper level ridge will hold through Tuesday. Southern
stream trough will move across the area Wed-Thu. Upper level ridge
will then build again next weekend. Tropical wave or weak low pressure
will move across the area Thursday.
Discussion...dry weather regime expected to continue through Tuesday
under upper level ridge and building surface high pressure north of
the region. Only a slight relief to the hot weather expected till then
under lowering 1000-850 mb thicknesses and slightly cooler 925 mb
Rain chances begin to improve somewhat Wednesday night and especially
Thursday with the passage of a tropical wave or possible weak low pressure
system. However...12z gefs ensemble guidance has trended dryer
when compared to runs 24 and 48 hours ago and more to the northeast
with associated precipitation shield with this wave keeping most of the
active weather over the Leeward Islands. Upper level ridge begins to
build again next weekend with slight drying and forcing
diminishing considerably. So it appears the last week of October
will end in the dry side similar to previous weeks.
Aviation...VFR conditions expected next five days with no sig weather.
A rain showers or thunderstorms and rain possible at jmz and jbq each afternoon but probs
too low to include in forecast.
Marine...winds 10 knots or less through Monday. Winds strengthen Tuesday
and Wednesday to 15-20 knots as pressure gradient tightens in response to
building high pressure north of the region. Trades weaken Wednesday night
through next sun as tropical wave or weak low pressure moves across
the area. Seas 2-4 feet through Monday then build 4-6 feet Tuesday-Wednesday in
mixed north swells and easterly wind waves.
Climate...a record high temperature of 93f degrees was set today at
the lmm sju int'l Airport. This tied the old record of 93 set in
Preliminary point temps/pops...
sju 78 91 77 89 / 10 10 20 20
stt 80 88 79 89 / 10 10 30 30