Area Forecast Discussion
Issued by NWS San Juan, PR
FXCA62 TJSJ 011003
Area Forecast Discussion
National Weather Service San Juan PR
603 AM AST FRI JUL 1 2016
.SYNOPSIS...A tropical wave will move through the area today
through Saturday with showers and thunderstorms. Somewhat drier
weather is expected Sunday and Monday, but there is still
sufficient moisture and instability for showers and isolated
thunderstorms in western Puerto Rico. Tropical waves this weekend
and Tuesday will keep winds stronger. Some saharan dust is
expected but it will increase during the week next week.
At upper levels...A cut-off low just north of Hispaniola will move
across Cuba during the weekend and the early part of next week.
Another low will cut off northeast of the Leeward islands early on
Sunday and wander north of the Anegada passage before returning to
its original position late next week. Upper level flow will
generally be weak.
At mid levels...High pressure will continue across the sub-
tropics through early next week. A trough will dig toward the
Leeward islands from the north northwest the remainder of the
week. Another tropical wave near 50 west Saturday night will move
across the local area Monday night and Tuesday.
At lower levels...High pressure over the northeast Atlantic will
move over the Azores over the weekend causing a ridge that
stretches to the northern Bahama islands to become more
pronounced. The ridge and the the moderate to fresh trade winds
will weaken during the week when weak low pressure gains control
of the western Atlantic.
.DISCUSSION...The first band of a tropical wave moved into the
Caribbean south of Saint Croix overnight with clusters of
thunderstorms that remained close to the southern border of our
forecast area as they moved west. Tops occasionally reached 50
kft. Showers and thunderstorms are expected to develop over
western and interior Puerto Rico during the day and will have
some assistance from the upper level low about 400 miles to the
northwest. The back of the wave will cross through late Saturday
with another round of showers and thunderstorms. Drier air will
prevail Sunday and Monday, but strong heating will promote showers
and thunderstorms over western and interior Puerto Rico during the
afternoons. A second wave is due to pass through Monday night and
Tuesday with similar moisture. Low pressure forming in the
Atlantic north of the area late next week will also bring
additional moisture to the area on Friday of next week.
.AVIATION...The tropical wave moving west across the Caribbean
Sea will increase clouds and SHRA over the local flying area. This
will result in SCT/BKN Cigs around FL025-100 thru the morning
hours...spreading across the interior and western sections of PR
during the afternoon...impacting mainly TJBQ/TJMZ. East winds at
10- 15kt with higher gusts near SHRA and sea breeze variation
.MARINE...Winds in the tropical wave will keep seas agitated and
rough. Conditions will approach small craft advisory conditions
on Sunday and spread over the outer waters of the area Monday and
.PRELIMINARY POINT TEMPS/POPS...
SJU 88 80 90 79 / 50 40 50 30
STT 89 79 88 79 / 40 60 60 20