Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Juan PR
1044 PM AST sun Dec 28 2014
Update...passing isolated to scattered showers were observed mainly
over the Atlantic and Caribbean waters. A few of them reached
parts of the local islands but rainfall amounts were not
significant. No changes made to weather grids as forecast is on
track. Increased wave heights to 8 feet at the end of the forecast
period as strong easterlies develop across the Atlantic Ocean.
Aviation...mainly VFR conditions will prevail across all taf sites
through at least 29/12z. Some passing showers are possible over
tist...tist...tjsj...and tjbq. Low level winds will be mainly from
the east northeast at 10 kts.
Marine...as indicated by buoys 41043/41053 NE swell continues at
6-8 feet across the Atlantic waters. Breaking waves across the
exposed north and east facing beaches of all local islands should
stay under 10 feet. Swell will slowly subside until at least early
Tuesday. Winds will increase more by the end of the week across
the Atlantic and Caribbean waters increasing seas once again by
Previous discussion... /issued 320 PM AST sun Dec 28 2014/
Synopsis...moisture associated with an old frontal boundary will
linger across the local area through Monday night. Then...middle level
ridge over the western Caribbean will expand eastward into the
eastern Caribbean by Tuesday...generating a fair weather conditions
across the local islands. Although...a relatively stable pattern will
prevail through the end of the weekend...low level moisture embedded
in the trade winds will bring occasional showers across the islands.
Discussion...a weakening frontal boundary moved over the forecast
area this morning. As a result...cloudiness and shower activity
increased across the northeast Caribbean islands. Variably to mostly
cloudy skies with occasional showers of light to moderate intensity
have been observed across portions of the USVI and PR. The most
frequent showers affected the northern half of Puerto Rico this
morning while in the afternoon the cloudiness and light showers
moved over St. Croix and the southern and west portions of Puerto
Rico. The majority of the showers that affect the islands have been
light to moderate...therefore no significant rainfall accumulation
have been observed over the local islands so far today.
For tonight and overnight...the trade winds will shift from the
northeast to east...resulting in a few passing showers across the
windward side of the islands. Remnant of the old frontal boundary
will linger across the local region through late Monday night.
Operational models suggest a easterly perturbation associated with
the remnants of the front will cross the PR/USVI between Monday
night and Tuesday morning. This perturbation in the easterly winds
will enhance the low level convergence across the northeast Caribbean
islands...resulting in at least scattered showers across USVI and
the eastern half of Puerto Rico on Monday night.
Then...middle level ridge over the western Caribbean will expand eastward
into the eastern Caribbean by Tuesday. This will result in generally
a fair weather pattern across the local islands through the end of
the year. Although...a relatively stable pattern will prevail most
of the week...low level moisture embedded in the trade winds will
bring occasional light showers across the islands from time to
Preliminary point temps/pops...
sju 70 82 71 84 / 60 60 50 20
stt 74 87 76 86 / 60 60 50 20
Coastal waters...Small Craft Advisory until 6 PM 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 USVI and Culebra out 10 nm-
coastal waters of southern USVI Vieques and eastern Puerto
Rico out 10 nm-Mona Passage southward to 17n.
Small Craft Advisory until midnight AST Monday night for coastal
waters of northwestern Puerto Rico out 10 nm.
Small Craft Advisory until noon AST Tuesday for coastal waters
of northern Puerto Rico out 10 nm.