Re: Caribbean - Central America Weather
Posted: Mon Sep 09, 2019 5:02 am
Area Forecast Discussion
National Weather Service San Juan PR
455 AM AST Mon Sep 9 2019
.SYNOPSIS...
An upper level trough will continue to provide instability to the
area, and shower and convective activity are anticipated for this
afternoon, especially over western Puerto Rico, even as the
moisture decreases throughout the region. Tomorrow into midweek,
with the upper trough slowly pulling away from the area and the
decreasing trend for moisture continuing, somewhat decreased
shower activity is likely, though local effects and diurnal
heating will still allow for the generation of showers over
interior and western Puerto Rico.
&&
.SHORT TERM...Today through Wednesday...
Isolated trade wind showers are continuing east and north of
Puerto Rico this morning, and will likely persist through the late
morning hours from fairly high precipitable water values. Though
high moisture content is expected to slowly decline over the next
few days, there will still be ample moisture to help kick off
showers and thunderstorms for later on this afternoon.
Furthermore, an upper tropospheric trough moving to our west could
enhance these showers and thunderstorms, leading to heavy rain
and frequent lightning. The potential for urban and small stream
flooding will once again become an issue, as has been the case the
past few days. Given winds from the east for this afternoon,
showers will generally form directly over and to the west of the
Puerto Rico high terrain. Weak steering winds will result in slow
moving thunderstorms which will enhance the flooding risk.
Conditions become slightly less conducive for shower activity for
Tuesday and more so Wednesday. The aforementioned upper low will move
to our north for Tuesday, but could still enhance any developing
showers. Moisture content will continue its slow decline, but
showers and thunderstorms are still expected, albeit less widespread
and intense than this afternoon. Winds will still remain fairly slow
in the lower troposphere, leading to slow moving showers once again,
and centered over western Puerto Rico. Similar conditions exist for
Wednesday, though more west southwest winds will put the center of
shower activity over the NW part of Puerto Rico.
.LONG TERM...Thursday through Monday...
A TUTT is expected to be positioned to the N/NE of the islands on
Thursday, remaining somewhat stationary into Friday, then
progressing westward/northwestward through the weekend into Monday.
A somewhat drier airmass over the region on Thursday will likely
decrease somewhat the shower and convective activity caused by local
effects and diurnal heating in the afternoon and into the night. A
more moist airmass is expected to push westward into the area
starting on Friday, with increasing moisture through the weekend.
On Sunday, the GFS shows a tropical cyclone developing near the
Leeward Islands and moving west/northwestward, moving south of the
region on Monday. The ECMWF, however, has a more slowly
developing and slower moving tropical cyclone, which also has a
more north track, taking it well north of Puerto Rico and the U.S.
Virgin Islands on Tuesday; this solution also suggests a
significantly weaker system. Considering the lead time and lack of
model agreement, there is low confidence in any forecast for this
potential future tropical cyclone, and as such its possible
existence is not reflected in the forecast. Either way, a tropical
wave is likely to pass by or over the region early next week,
providing increased moisture.
&&
.AVIATION...
Mostly VFR conditions are prevailing across all TAF
sites this morning. However, off and on VCSH is occurring for TISX
and TIST, and this is expected to continue for the next several
hours. After 09/16z SHRA/TSRA are expected in and around TJMZ and
TJBQ, resulting in MVFR cond. A smaller chance for VCSH exists for
TJSJ. Sea breeze winds around 10 mph are expected, with light and
variable winds for the overnight hours.
&&
.MARINE...
Typical marine conditions will continue to prevail today, with
wave heights up to 3-5 feet, and winds out of the SE at 5-10
knots. A small northerly sweel will persist in the area,
especially in Atlantic waters. Overnight tonight, there is the
potential for occasional seas up to 6 feet, mainly in offshore
Atlantic waters. There is a moderate risk of rip currents today at
northern beaches of Puerto Rico, Culebra, and the U.S. Virgin
Islands, as well as southwestern Puerto Rico, with a low risk
elsewhere.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 91 78 / 30 30 30 30
STT 89 79 90 80 / 30 30 30 30
National Weather Service San Juan PR
455 AM AST Mon Sep 9 2019
.SYNOPSIS...
An upper level trough will continue to provide instability to the
area, and shower and convective activity are anticipated for this
afternoon, especially over western Puerto Rico, even as the
moisture decreases throughout the region. Tomorrow into midweek,
with the upper trough slowly pulling away from the area and the
decreasing trend for moisture continuing, somewhat decreased
shower activity is likely, though local effects and diurnal
heating will still allow for the generation of showers over
interior and western Puerto Rico.
&&
.SHORT TERM...Today through Wednesday...
Isolated trade wind showers are continuing east and north of
Puerto Rico this morning, and will likely persist through the late
morning hours from fairly high precipitable water values. Though
high moisture content is expected to slowly decline over the next
few days, there will still be ample moisture to help kick off
showers and thunderstorms for later on this afternoon.
Furthermore, an upper tropospheric trough moving to our west could
enhance these showers and thunderstorms, leading to heavy rain
and frequent lightning. The potential for urban and small stream
flooding will once again become an issue, as has been the case the
past few days. Given winds from the east for this afternoon,
showers will generally form directly over and to the west of the
Puerto Rico high terrain. Weak steering winds will result in slow
moving thunderstorms which will enhance the flooding risk.
Conditions become slightly less conducive for shower activity for
Tuesday and more so Wednesday. The aforementioned upper low will move
to our north for Tuesday, but could still enhance any developing
showers. Moisture content will continue its slow decline, but
showers and thunderstorms are still expected, albeit less widespread
and intense than this afternoon. Winds will still remain fairly slow
in the lower troposphere, leading to slow moving showers once again,
and centered over western Puerto Rico. Similar conditions exist for
Wednesday, though more west southwest winds will put the center of
shower activity over the NW part of Puerto Rico.
.LONG TERM...Thursday through Monday...
A TUTT is expected to be positioned to the N/NE of the islands on
Thursday, remaining somewhat stationary into Friday, then
progressing westward/northwestward through the weekend into Monday.
A somewhat drier airmass over the region on Thursday will likely
decrease somewhat the shower and convective activity caused by local
effects and diurnal heating in the afternoon and into the night. A
more moist airmass is expected to push westward into the area
starting on Friday, with increasing moisture through the weekend.
On Sunday, the GFS shows a tropical cyclone developing near the
Leeward Islands and moving west/northwestward, moving south of the
region on Monday. The ECMWF, however, has a more slowly
developing and slower moving tropical cyclone, which also has a
more north track, taking it well north of Puerto Rico and the U.S.
Virgin Islands on Tuesday; this solution also suggests a
significantly weaker system. Considering the lead time and lack of
model agreement, there is low confidence in any forecast for this
potential future tropical cyclone, and as such its possible
existence is not reflected in the forecast. Either way, a tropical
wave is likely to pass by or over the region early next week,
providing increased moisture.
&&
.AVIATION...
Mostly VFR conditions are prevailing across all TAF
sites this morning. However, off and on VCSH is occurring for TISX
and TIST, and this is expected to continue for the next several
hours. After 09/16z SHRA/TSRA are expected in and around TJMZ and
TJBQ, resulting in MVFR cond. A smaller chance for VCSH exists for
TJSJ. Sea breeze winds around 10 mph are expected, with light and
variable winds for the overnight hours.
&&
.MARINE...
Typical marine conditions will continue to prevail today, with
wave heights up to 3-5 feet, and winds out of the SE at 5-10
knots. A small northerly sweel will persist in the area,
especially in Atlantic waters. Overnight tonight, there is the
potential for occasional seas up to 6 feet, mainly in offshore
Atlantic waters. There is a moderate risk of rip currents today at
northern beaches of Puerto Rico, Culebra, and the U.S. Virgin
Islands, as well as southwestern Puerto Rico, with a low risk
elsewhere.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 89 79 91 78 / 30 30 30 30
STT 89 79 90 80 / 30 30 30 30