Post by cycloneye on Jul 8, 2017 5:00:52 GMT -6
Area Forecast Discussion
National Weather Service San Juan PR
510 AM AST Sat Jul 8 2017
.SYNOPSIS...A tropical wave is passing through the Mona passage this
morning and will continue to carry moisture with it today. There
will be a dry slot before moisture from the next tropical wave--
that was previously tropical depression number 4--moves through on
Sunday. Then an area of drier air loaded with Saharan dust will
come in Monday and Tuesday. An easterly wave will move through on
Wednesday with drying Thursday night.
&&
.SHORT TERM...As the wave left the region overnight, the lingering moisture
brought showers across the U.S. Virgin Islands and the east half
portion of Puerto Rico. These showers produced periods of moderate
to heavy rainfall, which result in hazardous driving conditions as
well as ponding of water on roadways and in poor drainage areas.
This morning, passing showers will continue across the windward
sections. However, the west half section of Puerto Rico should
remain with little or no shower activity. Then, the combination of
the available moisture and local effects will enhance showers and
thunderstorms development mainly across the interior and west
sections of Puerto Rico. At the same time, patches of moisture will
bring showers across the Northern U.S. Virgin Islands, which in turn
will move westward into Culebra and the east municipalities of
Puerto Rico.
By Sunday, a tropical wave is forecast to pass north of the local
islands Sunday. Although the bulk of moisture will move across the
Atlantic waters, shower and thunderstorm activity is expected to
increase through Sunday. This tropical wave is surrounded with
Saharan dust which could make it way through the islands. As the
tropical wave moves into the Western Atlantic, a southerly wind flow
is expected to prevail Sunday and Monday. Under this southerly wind
flow warm temperatures could lead to heat indices around the high
90s and low 100s each afternoon. Another air mass with Saharan
dust particulate is forecast to reach us by Monday.
.LONG TERM...Tuesday through Friday
The TUTT low to the northeast of the area will wander toward us
for a few days but will begin to lose strength as it becomes
nearly north of the area at about 500 miles. This will leave high
pressure over the area at upper levels. An approaching tropical
wave will shift the low level winds back to the northeast briefly
later on Tuesday, but we will return to a more southeasterly flow
afterward with its passage on Wednesday. In the meantime moisture
levels remain normal to slightly above normal until around midday
on Thursday to create scattered showers almost everywhere and
afternoon thunderstorms in the western portions of Puerto Rico.
After a drier night, a larger envelope of good moisture enters
the eastern Caribbean on Friday and will begin to increase
showers and thunderstorms.
Beyond Friday we are continuing to monitor model outputs that
suggest a tropical system will move into the Caribbean Friday
night and affect most of the area over the weekend with winds and
rain. Model outputs are still wavering on the track of this
system, but conditions appear favorable for development.
&&
.AVIATION...SHRA expected to continue across TJSJ/TIST/TISX and
TJPS at times during the morning hours. Expected to diminish around
08/12z. SHRA/TSRA are expected to develop across the west/interior
PR btwn 08/17-22z. MVFR conds could be required at TJBQ/TJMZ and
possibly at TJSJ/TIST during the afternoon. Calm to light and vrb
winds, increasing at 10 to 15 knots aft 08/13z with higher gusts in
sea breeze variations and showers.
&&
.MARINE...Seas in the northeast corner of the local outer Atlantic
waters continue to run 5 to 6 feet and winds in the nearshore
Atlantic waters are occasionally reaching 18 knots. Condtions are
expected to become more tranquil after Sunday. Small craft
advisories are not expected before Saturday of next week.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 90 80 / 50 30 50 20
STT 88 79 88 81 / 50 30 40 20
National Weather Service San Juan PR
510 AM AST Sat Jul 8 2017
.SYNOPSIS...A tropical wave is passing through the Mona passage this
morning and will continue to carry moisture with it today. There
will be a dry slot before moisture from the next tropical wave--
that was previously tropical depression number 4--moves through on
Sunday. Then an area of drier air loaded with Saharan dust will
come in Monday and Tuesday. An easterly wave will move through on
Wednesday with drying Thursday night.
&&
.SHORT TERM...As the wave left the region overnight, the lingering moisture
brought showers across the U.S. Virgin Islands and the east half
portion of Puerto Rico. These showers produced periods of moderate
to heavy rainfall, which result in hazardous driving conditions as
well as ponding of water on roadways and in poor drainage areas.
This morning, passing showers will continue across the windward
sections. However, the west half section of Puerto Rico should
remain with little or no shower activity. Then, the combination of
the available moisture and local effects will enhance showers and
thunderstorms development mainly across the interior and west
sections of Puerto Rico. At the same time, patches of moisture will
bring showers across the Northern U.S. Virgin Islands, which in turn
will move westward into Culebra and the east municipalities of
Puerto Rico.
By Sunday, a tropical wave is forecast to pass north of the local
islands Sunday. Although the bulk of moisture will move across the
Atlantic waters, shower and thunderstorm activity is expected to
increase through Sunday. This tropical wave is surrounded with
Saharan dust which could make it way through the islands. As the
tropical wave moves into the Western Atlantic, a southerly wind flow
is expected to prevail Sunday and Monday. Under this southerly wind
flow warm temperatures could lead to heat indices around the high
90s and low 100s each afternoon. Another air mass with Saharan
dust particulate is forecast to reach us by Monday.
.LONG TERM...Tuesday through Friday
The TUTT low to the northeast of the area will wander toward us
for a few days but will begin to lose strength as it becomes
nearly north of the area at about 500 miles. This will leave high
pressure over the area at upper levels. An approaching tropical
wave will shift the low level winds back to the northeast briefly
later on Tuesday, but we will return to a more southeasterly flow
afterward with its passage on Wednesday. In the meantime moisture
levels remain normal to slightly above normal until around midday
on Thursday to create scattered showers almost everywhere and
afternoon thunderstorms in the western portions of Puerto Rico.
After a drier night, a larger envelope of good moisture enters
the eastern Caribbean on Friday and will begin to increase
showers and thunderstorms.
Beyond Friday we are continuing to monitor model outputs that
suggest a tropical system will move into the Caribbean Friday
night and affect most of the area over the weekend with winds and
rain. Model outputs are still wavering on the track of this
system, but conditions appear favorable for development.
&&
.AVIATION...SHRA expected to continue across TJSJ/TIST/TISX and
TJPS at times during the morning hours. Expected to diminish around
08/12z. SHRA/TSRA are expected to develop across the west/interior
PR btwn 08/17-22z. MVFR conds could be required at TJBQ/TJMZ and
possibly at TJSJ/TIST during the afternoon. Calm to light and vrb
winds, increasing at 10 to 15 knots aft 08/13z with higher gusts in
sea breeze variations and showers.
&&
.MARINE...Seas in the northeast corner of the local outer Atlantic
waters continue to run 5 to 6 feet and winds in the nearshore
Atlantic waters are occasionally reaching 18 knots. Condtions are
expected to become more tranquil after Sunday. Small craft
advisories are not expected before Saturday of next week.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 88 78 90 80 / 50 30 50 20
STT 88 79 88 81 / 50 30 40 20