National Weather Service San Juan PR
516 AM AST Mon Feb 18 2019
.SYNOPSIS...
The combination of a dry air mass and a mid-to-upper level high
pressure will maintain stable weather conditions across the
islands through much of this week. However, the seasonal advective
pattern associated with patches of low level moisture will bring
occasional showers from time to time. The mid-level high pressure
will make difficult afternoon convection across the western
sections especially today.
&&
SHORT TERM...Today through Wednesday...
Mainly stable weather conditions will prevail across the forecast
area throughout the period as a mid to upper-level ridge will build
overhead. In addition, this ridging pattern will also result in the
strengthening of a fairly robust low-level inversion, which will
serve to maintain moisture profiles below normal. Therefore, most of
the area is expected to observe mainly fair weather conditions. Any
showers that do affect the local area will be as a result of the
small patches of low-level moisture embedded within the trade wind
flow, however, the activity is expected to be isolated and brief
with very light accumulations. A surface high pressure across the
east-central Atlantic and another surface high pressure set to move
across the western Atlantic between late Tuesday and Wednesday will
result in a tightening of the local pressure gradient. This will
result in breezy conditions with winds expected to range between 10
and 20 mph with higher gusts.
.LONG TERM...Thursday through Tuesday...
Fair weather conditions will prevailed through the long term
forecast. A mid-upper level ridge will promote subsidence limiting
convection across the islands. Forecast soundings continues to
suggest the presence of a strong trade wind inversion which is
consistence with drier than normal conditions at mid-to-upper
levels as depicted in the vertical cross-section. However, breezy
trade winds will bring patches of low level moisture with
embedded clouds and showers across the windward sections of Puerto
Rico and the U.S. Virgin Islands each days. A similar weather
pattern will persist throughout the long term forecast.
A migratory high pressure across the Atlantic waters will
strengthen the local pressure gradient increasing the easterly
winds between 15 and 25 knots especially across the local waters
and coastal sections by mid-week into the upcoming weekend.
&&
.AVIATION...
VFR conditions are expected to prevail across all terminals
throughout the forecast period. Winds less than 10 kts through
18/14z, becoming east between 12 and 18 kts with higher gusts and
sea breeze variations afterwards.
&&
.MARINE...
Mariners should exercise caution across most of the local waters
as easterly winds are forecast to increase between 15 and 20
knots. Therefore, choppy seas will range between 4 and 6 feet
across most of the expose local water, while the protected areas
could expect seas at 4 feet or less.
A surface high pressure building across the Central Atlantic will
increase winds and seas across the Caribbean Offshore Waters and
Mona Passage late tonight. Conditions will become hazardous with
increasing seas up to 7 feet and winds between 15 and 25 knots
For that reason, a small craft advisory is in effect from late
tonight through at least Friday. Model guidance continue to
suggest hazardous winds and seas spreading across most of the
local waters after Tuesday night and continuing through the
upcoming weekend.
&&
.FIRE WEATHER...
Fire danger statements will be issued along the southern plains of
Puerto Rico as RH values are expected to drop significantly
between Cabo Rojo and Camp Santiago Raws Stations. The limiting
factor will be the winds which are not expected to reach Red Flag
Warning criteria.
A drying trend is expected to persist through much of this week.
Winds are expected to increase after late tonight and continuing
through the weekend. KBDI values shows that soils are significantly
dry with values above 700 at Cabo Rojo and Camp Santiago. Given
that the forecast calls for the continuation of a relatively dry
weather pattern and increasing winds, the chance for fire weather
conditions will remain high through the upcoming work-week.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 85 72 84 74 / 0 20 20 20
STT 84 72 84 73 / 0 20 20 20