Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
258 PM AST Sat Dec 7 2013
Synopsis...strong surface high pressure near Bermuda will maintain
a strong northeast flow across the local region through Tuesday.
Upper low east of the local islands will retrogress into the
Caribbean waters and meander over that area through early next
week. A middle level high pressure ridge will build over the western
Atlantic...promoting a generally stable pattern across the region
most of the work week.
Discussion...loops of water vapor imagery reveals a cyclonic
rotation associated with an upper low over the northern Leeward
Islands this afternoon. Infrared imagery have showed clouds and showers
moving quickly across the islands all day. The brisk northeast
flow has carried occasional showers across Puerto Rico...Culebra...
Vieques and the U.S Virgin Islands since midnight. The fast movement
of these showers have limited the rainfall accumulation over land
areas. Rain gages and radar estimates suggest rainfall accumulations
up to 0.75 inches in portions of the northeast and north central
Puerto Rico. Elsewhere...rainfall accumulations have been less
than one quarter of an inch.
Little change in the weather pattern is expected over the next
few days. Basically...the strong northeast flow will continue to
bring periods of showers across the windward side of the local
islands from time to time. However...mid-level energy revolving
around the upper low east of the islands...may enhance the
convective instability over the local area on Sunday...resulting
in isolated thunderstorms and periods of locally heavy rainfall.
Then...mid-level ridge will favor the erosion of the available
moisture across the northeast Caribbean Monday through Thursday.
Aviation...periods of MVFR conditions and mountain obscurations
will remain possible across the local flying area in rain showers and isolated
thunderstorms and rain. Main concern will continue to be the strong NE winds of 20-25
Marine...the combination of a short-period northeast swell and
locally generated wind waves will continue to produce hazardous
seas across the regional waters at least Tuesday. As a result...a
high surf advisory and a Small Craft Advisory remain in effect
through at least Monday and Tuesday...respectively.
Preliminary point temps/pops...
sju 72 83 72 84 / 40 60 20 20
stt 73 84 75 87 / 40 60 20 20
PR...high surf advisory until 6 am AST Monday for Culebra-north
Central-Northeast-northwest-San Juan and vicinity-southeast-
Vi...high surf advisory until 6 am AST Monday for St Croix-St.
Thomas/St. John/adjacent islands.
Small Craft Advisory until 3 PM AST Monday for coastal waters of
southern Puerto Rico out 10 nm.
Small Craft Advisory until 9 am AST Tuesday for Anegada Passage
southward to 17n-Atlantic waters of Puerto Rico and USVI from
10nm to 19.5n-Caribbean waters of Puerto Rico from 10 nm to
17n-coastal waters of northern Puerto Rico out 10 nm-
coastal waters of northern USVI and Culebra out 10 nm-
coastal waters of northwestern Puerto Rico out 10 nm-
coastal waters of southern USVI Vieques and eastern Puerto
Rico out 10 nm-Mona Passage southward to 17n.