Area forecast discussion
National Weather Service San Juan PR
309 PM AST Wednesday Jun 19 2013
Discussion...upper tropospheric trough is rapidly drawing
moisture northward and...so far...most of the thunderstorms are
going too. A large band of thunderstorms remains in the Caribbean
south of USVI at 15n to 17n and it is wrapping into St. Croix and
to Culebra. But none of these are likely to move towards PR soon
so am not sure about carrying very many showers into evening. Onshore
flow may regenerate some showers especially on the southeast PR
slopes in next few hours...and it currently shows a little
potential for that.
The southern end of the thunderstorms near 15n/65.5w is handled by
the GFS as a weak remnant of the tropical wave which moves
northwest. GFS GOES a little nuts over it as it encounters good
250 mb divergence tonight. The resulting covergence at 700 mb and
divergence at 250 mb...especially at Thursday/12z south of PR at 16.6n
looks like convective feedback and will not bite. So am dismissing
this as GFS shows it moving over the island on Thursday. Convective
potential especially does not look significant since strong dry
advection will occur as the moist plume continues moving west at
25 knots...having reached Antilles at this time.
&&
Aviation...shra/tsra grdlly decr but threat of MVFR/IFR still
posbl. Moisture to drop off during Thursday daytime. Wind below fl100
mainly southeast 15-25 knots.
&&
Marine...Small Craft Advisory conditions to continue into Thursday but
gradually diminish.
&&
Preliminary point temps/pops...
sju 75 86 77 88 / 70 20 0 10
stt 77 86 78 88 / 90 20 10 10
&&
Sju watches/warnings/advisories...
PR...none.
Vi...none.
Coastal waters...Small Craft Advisory until midnight AST Thursday night for
Anegada Passage southward to 17n.
Small Craft Advisory until 6 am AST Friday for 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 southern
USVI Vieques and eastern Puerto Rico out 10 nm.
Small Craft Advisory until noon AST Thursday for coastal waters
of southern Puerto Rico out 10 nm.
Small Craft Advisory until 3 PM AST this afternoon for Mona
Passage southward to 17n.
Small Craft Advisory until 6 am AST Friday for Mona Passage
southward to 17n.
Small Craft Advisory until 7 PM AST this evening for coastal
waters of northwestern Puerto Rico out 10 nm.
Small Craft Advisory until 6 am AST Thursday for coastal waters
of northern Puerto Rico out 10 nm.
Small Craft Advisory until 6 PM AST Thursday for coastal waters
of northern USVI and Culebra out 10 nm.
&&
$$
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