Re: Caribbean - Central America Weather
Posted: Thu Aug 06, 2020 4:39 am
Area Forecast Discussion
National Weather Service San Juan PR
440 AM AST Thu Aug 6 2020
.SYNOPSIS...
After some scattered showers throughout the day today, a tropical
wave will arrive tomorrow that will enhance shower activity across
the region. Thereafter, drier than normal conditions will prevail
for the next several days, with mild to moderate amounts of
Saharan dust. Another tropical wave is forecast to arrive next
Wednesday, though models disagree on the timing and intensity.
&&
.SHORT TERM...Today through Saturday
An upper-level low moving into the region is eroding the mid-level
ridge aloft. A surge of low-level moisture is promoting frequent
passing showers across the local waters, and some of them are moving
into the windward sections of PR/USVI. Later today, a slot of dry
air will filter into the region limiting shower activity. Winds are
forecast to continue from the east to east-southeast promoting
afternoon convection across the interior and northwest quadrant of
Puerto Rico, and downwind from the U.S. Virgin Islands and from El
Yunque. Periods of moderate to heavy showers in the form of
streamers are possible across the San Juan metro area and surrounding
municipalities. Thunderstorm activity will deteriorate weather
conditions, and urban and small stream flooding is possible across
the interior and western sections of Puerto Rico this afternoon.
A tropical wave across the tropical Atlantic, near the longitude
55W, will propagate into the region by Friday afternoon. Although
the bulk of moisture will move off to the south of the islands
across the Caribbean waters, the instability and the moisture field
associated with it will increase the potential for showers and
thunderstorms across Puerto Rico and the U.S. Virgin Islands. Late
Friday night into Saturday, a dry air mass with Saharan dust
particulate will be the dominant weather feature across the islands.
Therefore, expect limited showers activity, hazy skies and warm to
hot temperatures.
.LONG TERM...
Generally speaking, the long-term period is expected to be drier
than normal, with the exception of a tropical wave for the middle of
next week. To kick off the week, high pressure will dominate our
region at all levels, and this will promote mostly dry conditions.
Model soundings look particularly dry and warm at mid-levels, and
that will keep showers weak for the most part. Passing showers
are still possible for Monday and Tuesday. Though they are
expected to be weak, persistent showers over a given area can
still cause localized flooding. For both days, the best chance
for showers is over western Puerto Rico in the afternoon.
On Wednesday a tropical wave is expected to arrive sometime during
the daytime or evening. Models somewhat disagree on the timing and
intensity, with the European model forecasting a later and weaker
wave. If warming from the sun can occur before the wave arrives,
this could prime the atmosphere for strong showers. However, there
is still plenty of uncertainty regarding this feature.
Furthermore, the wave will have a lot of work to do to clear out
the very dry and warm air expected for earlier in the weak, and
this weakens the potential of this wave. Thereafter, more dry air
moves in for Thursday, with long-range models suggesting another
wave on Friday.
&&
.AVIATION...
VFR conditions are expected to prevail through 06/18Z. However, VCSH
will affect IST/ISX/JSJ at times. SHRA/TSRA will develop across the
mountains and western sections of PR btwn 06/16-23z, as well as
downwind from the USVI. The heaviest activity is expected near JBQ,
and could create MVFR or even brief IFR conds. Surface winds will
continue from the E-ESE at less than 10 knots, increasing around 15
kt with sea breeze variations and higher gust after 06/13z.
&&
.MARINE...
Tranquil seas are expected for the next few days, with seas below
5 feet. Winds will generally be around 10 to 15 knots, though
winds may reach 15 to 20 knots near the coast of the Atlantic and
Caribbean. Winds and seas increase behind a tropical wave moving
in tomorrow. A low risk of rip currents is forecasted for
everywhere except a moderate risk for the north central coast of
Puerto Rico.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 91 78 / 30 20 60 30
STT 89 79 90 79 / 40 30 50 30
National Weather Service San Juan PR
440 AM AST Thu Aug 6 2020
.SYNOPSIS...
After some scattered showers throughout the day today, a tropical
wave will arrive tomorrow that will enhance shower activity across
the region. Thereafter, drier than normal conditions will prevail
for the next several days, with mild to moderate amounts of
Saharan dust. Another tropical wave is forecast to arrive next
Wednesday, though models disagree on the timing and intensity.
&&
.SHORT TERM...Today through Saturday
An upper-level low moving into the region is eroding the mid-level
ridge aloft. A surge of low-level moisture is promoting frequent
passing showers across the local waters, and some of them are moving
into the windward sections of PR/USVI. Later today, a slot of dry
air will filter into the region limiting shower activity. Winds are
forecast to continue from the east to east-southeast promoting
afternoon convection across the interior and northwest quadrant of
Puerto Rico, and downwind from the U.S. Virgin Islands and from El
Yunque. Periods of moderate to heavy showers in the form of
streamers are possible across the San Juan metro area and surrounding
municipalities. Thunderstorm activity will deteriorate weather
conditions, and urban and small stream flooding is possible across
the interior and western sections of Puerto Rico this afternoon.
A tropical wave across the tropical Atlantic, near the longitude
55W, will propagate into the region by Friday afternoon. Although
the bulk of moisture will move off to the south of the islands
across the Caribbean waters, the instability and the moisture field
associated with it will increase the potential for showers and
thunderstorms across Puerto Rico and the U.S. Virgin Islands. Late
Friday night into Saturday, a dry air mass with Saharan dust
particulate will be the dominant weather feature across the islands.
Therefore, expect limited showers activity, hazy skies and warm to
hot temperatures.
.LONG TERM...
Generally speaking, the long-term period is expected to be drier
than normal, with the exception of a tropical wave for the middle of
next week. To kick off the week, high pressure will dominate our
region at all levels, and this will promote mostly dry conditions.
Model soundings look particularly dry and warm at mid-levels, and
that will keep showers weak for the most part. Passing showers
are still possible for Monday and Tuesday. Though they are
expected to be weak, persistent showers over a given area can
still cause localized flooding. For both days, the best chance
for showers is over western Puerto Rico in the afternoon.
On Wednesday a tropical wave is expected to arrive sometime during
the daytime or evening. Models somewhat disagree on the timing and
intensity, with the European model forecasting a later and weaker
wave. If warming from the sun can occur before the wave arrives,
this could prime the atmosphere for strong showers. However, there
is still plenty of uncertainty regarding this feature.
Furthermore, the wave will have a lot of work to do to clear out
the very dry and warm air expected for earlier in the weak, and
this weakens the potential of this wave. Thereafter, more dry air
moves in for Thursday, with long-range models suggesting another
wave on Friday.
&&
.AVIATION...
VFR conditions are expected to prevail through 06/18Z. However, VCSH
will affect IST/ISX/JSJ at times. SHRA/TSRA will develop across the
mountains and western sections of PR btwn 06/16-23z, as well as
downwind from the USVI. The heaviest activity is expected near JBQ,
and could create MVFR or even brief IFR conds. Surface winds will
continue from the E-ESE at less than 10 knots, increasing around 15
kt with sea breeze variations and higher gust after 06/13z.
&&
.MARINE...
Tranquil seas are expected for the next few days, with seas below
5 feet. Winds will generally be around 10 to 15 knots, though
winds may reach 15 to 20 knots near the coast of the Atlantic and
Caribbean. Winds and seas increase behind a tropical wave moving
in tomorrow. A low risk of rip currents is forecasted for
everywhere except a moderate risk for the north central coast of
Puerto Rico.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 90 78 91 78 / 30 20 60 30
STT 89 79 90 79 / 40 30 50 30