Area forecast discussion
National Weather Service San Juan PR
258 PM AST Tuesday Jun 18 2013
Discussion...upper tropospheric trough currently north of PR/USVI
about 22.5n slowly drifting west will interact with a broad tropical
wave currently east of the Antilles...moving west at 25 knots. It is
already beginning to draw moisture northward and amplify the wave.
Several thunderstorm clusters across the Caribbean are producing
outflow boundaries moving along at 30 knots. East of the leewards
at 17z-18z a ship and near surface GOES satellite winds were
reporting 25-28 knots. These are concern enough to kick up the winds
and seas by Wednesday a little which increases the coverage of the Small
Craft Advisory. Also 12z GFS pushes 850-700 mb winds exceeding 35
knots over to northeast of PR/USVI by late Wednesday. This in addition to
the outflow boundaries already being generated suggest strong wind
gusts are possible in strong showers/thunderstorms.
Do not believe that significant flooding will be a threat since
ground is relatively dry and this wave is moving quickly. However
must especially watch the southeast PR coast as onshore flow could
cause persistent heavy showers there...most likely Wednesday evening.
Drying to occur Thursday morning and we return to rather dry conditions
with significant Saharan dust.
&&
Aviation...VFR most of tonite but rain showers/thunderstorms and rain to increase late and into
Wednesday. Rain showers/thunderstorms and rain late this afternoon near tjmz will cause periods MVFR maybe
IFR...obscured mountains in west PR. Wind below fl100 east 15-30 knots becoming east-southeast
20-35 knots Wednesday after.
&&
Marine...winds/seas increasing slightly through Wednesday but bigger
concern is possible higher conditions in/near showers/thunderstorms
on Wednesday/Wednesday night. Gusts to 35-40 knots will be possible.
&&
Preliminary point temps/pops...
sju 77 86 77 88 / 50 60 60 20
stt 78 87 78 88 / 50 70 40 20
&&
Sju watches/warnings/advisories...
PR...none.
Vi...none.
Coastal waters...Small Craft Advisory from 3 am Wednesday to 3 am AST Thursday
for Anegada Passage southward to 17n-coastal waters of
northern USVI and Culebra out 10 nm.
Small Craft Advisory until 3 am AST Friday for Caribbean waters
of Puerto Rico from 10 nm to 17n-coastal waters of southern
USVI Vieques and eastern Puerto Rico out 10 nm-Mona Passage
southward to 17n.
Small Craft Advisory from 8 PM Wednesday to 9 am AST Thursday
for coastal waters of southern Puerto Rico out 10 nm.
Small Craft Advisory from 9 PM Wednesday to 3 am AST Thursday
for coastal waters of northern Puerto Rico out 10 nm.
Small Craft Advisory until 3 am AST Friday for Atlantic waters of
Puerto Rico and USVI from 10nm to 19.5n.
&&
$$
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