National Weather Service San Juan PR
507 AM AST Sat Jul 30 2022
.SYNOPSIS...A passing tropical wave will continue to support
showers and isolated thunderstorms with the potential for urban
and small stream flooding today, followed by rapid drying with the
entrance of a Saharan Air Layer and associated drier air mass by
tonight into early week. The next rain produced is expected by
midweek, followed by a set of tropical waves by the end of the
workweek into the upcoming weekend. In the meantime, expect the
typical shower pattern highlighted by afternoon convective
development over western sections. Increasing winds will maintain
choppy to hazardous marine conditions and life-threatening rip
currents during the next few days. Above- normal heat indices are
also expected.
&&
.SHORT TERM...Today through Monday...
A tropical wave depicted on GOES-East imagery will bring a sharp
increase in moisture and breezy to windy easterlies today. The Total
Precipitable Water estimated by the satellite range between 1.90 and
2.10 (or even more) inches. This water content is above-normal for
July`s climatology (around the 75th percentile). In addition,
African Dust Particles are also present in our atmosphere, and some
haziness will also be present late today. This wave will promote
showery weather conditions across the islands, and thunderstorms may
affect the region too. Periods of moderate to heavy rain could
result in ponding of water in roads and poorly drained areas in
Puerto Rico and the U.S. Virgin Islands. We cannot rule out urban
and small stream flooding if persistent heavy rains affect the
islands, especially along the Cordillera Central, la Sierra de
Luquillo, the San Juan Metro-Area, or western PR. In addition to the
flooding threat, in coastal and urban areas without receiving
significant rainfall amounts, the combination between the maximum
temperatures and the moisture content could result in heat indices
above 100 degrees Fahrenheit by mid-morning into the afternoon.
Although patches of moisture embedded in the trades will promote a
seasonal weather pattern, consisting of passing showers across the
windward sections and afternoon convection across the western areas,
expect a drying trend after today`s wave. This dry air mass has
African Dust Particulate, promoting hazy skies throughout the short
term. Residents of Puerto Rico and the Virgin Islands should know
that on Sunday and Monday, the heat indices will reach and surpass
100s degrees Fahrenheit after mid-morning into the afternoon.
.LONG TERM...Tuesday through Saturday...
A surface high pressure meandering across the north Atlantic Ocean
will maintain a generally easterly wind flow at 10-20 mph through
the long-term forecast cycle. Nonetheless, various surface
features, including an induced trough and a set of tropical waves,
will cause winds to vary briefly in intensity and direction. These
same features are expected to produce measurable rainfall totals,
with the potential for ponding of water on roadways and poorly
drained areas to localized minor flooding. The first feature, a
surface-induced trough, will affect the area late Tuesday into
Wednesday, followed by a weak tropical wave on Thursday and yet
another broader tropical wave on Saturday. In the meantime, a
Saharan Air Layer and associated drier air will maintain generally
fair weather conditions and hazy skies. Daytime temperatures will
also vary with changes in the general wind flow, but heat indices
may peak into the lower to mid 100s each afternoon.
&&
.AVIATION...A tropical wave moving across the region, will bring
SHRA/TSRA, causing VCTS across the USVI this morning and later in
the afternoon. TSRA/SHRA will spread across most of PR by 30/15z and
will possibly affect TJSJ/TJPS/TJBQ. Winds will continue will
continue from the E/ESE around 10 kts, but gusty near SHRA. Winds
speed will range between 15 and 20 knots after 30/13z with sea
breeze variations and higher gusts near TSRA/SHRA.
&&
.MARINE...Increasing winds associated with the passage of a
tropical wave will maintain choppy to hazardous marine conditions
today. Across the local offshore Atlantic waters, where seas up to
7 feet are expected through early this afternoon, a Small Craft
Advisory remains in place. Elsewhere, small craft operators should
exercise caution due to moderate to locally fresh winds up to 20
knots and choppy seas of up to 6 feet. There is a high risk of rip
currents for beaches across the north coast of Puerto Rico and
beaches across the northern and eastern beaches of Culebra and
Saint Croix. A moderate risk of rip currents remains in place for
most remaining local beaches.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 87 79 89 80 / 80 50 50 30
STT 90 80 90 79 / 20 30 20 20