Small Craft Advisory 37, NWS JSJ

Area Forecast Discussion
National Weather Service San Juan PR
406 PM AST Wed Sep 27 2023

.SYNOPSIS...
Tropical Storm Philippe continues to move westward over the
central Atlantic. The remnants of this system may reach the
islands later in the weekend or early next week, increasing the
potential for rain and for flooding. However, there is still a lot
of uncertainty in this forecast, and the users are advised to stay
tuned for further updates.

Today, a surface trough moved in, causing plenty of showers. Less
rain is expected by the end of the week. Above normal temperatures
will persist for the next several days.

&&

.SHORT TERM...Tonight through Friday...

Tropical Storm Philippe now centered about 600 miles northeast of
the Leeward Islands is driving the trade winds out of the northeast
at around 15 knots. The water vapor satellite imagery also shows a
trough centered over the eastern Caribbean. Although the bulk of the
system remained over the waters, plenty of moisture moved in. As a
result, strong showers and thunderstorms developed, mainly along the
interior, and southwestern Puerto Rico. Rainfall accumulations were
as high as 1.5 to 2.0 inches in these areas. Almost all of the
islands, except northwestern Puerto Rico received rain. Even with
the rain, temperatures increased to the low and mid-90s, with heat
indices reaching the heat advisory criteria. In fact, Saint Croix
broke the maximum daily record...once again.

As the trough over the Caribbean continues to move west, drier air
will filter at the mid levels of the atmosphere, and shower activity
will diminish. It does not mean that it will not rain, since enough
moisture will remain at the lower levels. The pattern will be
seasonal, with passing showers affecting eastern Puerto Rico and the
U.S. Virgin Islands every morning, and active afternoons from the
interior and west. These areas in the afternoon may see isolated
urban and small stream flooding, river rises and mudslides.

As Tropical Storm Philippe continues to move to the west, the winds
will remain from the northeast, but they will be lighter, with
speeds around 8-11 knots on Thursday, and 5-8 knots on Friday. The
winds from the northeast may bring a slight release from the intense
heat, but with strong heating, some areas may still reach the 108
degree threshold for at least heat advisories product.

&&

.LONG TERM...Saturday through Tuesday/from prev discussion/

Philippe's final future will influence this weekend's weather
forecast; therefore, significant uncertainty is present. While
writing this discussion, Philippe had been weakening and will
weaken further. Based on the latest NHC forecast, Philippe will
weaken into a surface low pressure by the weekend. That said,
model guidance suggests that we may observe inclement weather as
early as Saturday due to the moisture field associated with
Philippe's remnant surface low pressure. The unstable weather
pattern could last into early next week as the lingering moisture
of the remnants could remain over the region of Puerto Rico and
the U.S. Virgin Islands.

Winds will veer from the north on Saturday to the east-southeast
on Sunday, becoming southerly Tuesday into the middle of next
week.

&&

.AVIATION...
A tutt low and induced low level trough will continue to
eastern Caribbean while enhancing SHRA/TSRA ovr the regional waters
and en route btw islands durg prd. SHRA/Isold TSRA ovr ctrl interior
and SW PR with VCTS mainly at TJSJ/TJMZ/TJPS and VCSH at USVI
terminals til 27/23Z. SCT ocnl BKN lyrs nr FL025...FL050 with WDLY
SCT SHRA/Isold TSRA durg prd.

&&

.MARINE...
A northeasterly swell from Tropical Storm Philippe is affecting
the local waters, with seas around 6 feet and occasionally
higher. Depending on the track of Philippe, seas may increase a
little more later this week or in the weekend. These conditions
will continue through much of the end of the workweek. There is a
high rip current risk for northern PR, Culebra and for eastern
St.Croix.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...High Rip Current Risk through late Thursday night for PRZ001-002-
     005-008-012.

VI...High Rip Current Risk through late Thursday night for VIZ002.

AM...None.
&&

SHORT TERM...DS
LONG TERM....ERG
PUBLIC DESK...RC