Since 2001 providing the latest information on tropical cyclone activity in the Atlantic Basin and the weather conditions in Puerto Rico.

Local Weather Conditions

 

National Weather Service Today's Weather Impact Levels

National Weather Service Forecast for: San Juan, Puerto Rico  

Updated: 4:43 am AST Dec 9, 2024

Hazardous Weather Outlook
Today

Today: Scattered showers.  Partly sunny, with a temperature falling to around 80 by 5pm. East wind around 14 mph.  Chance of precipitation is 40%.
Scattered
Showers
Hi 86 °F
Tonight

Tonight: Scattered showers.  Mostly cloudy, with a low around 74. East wind 8 to 10 mph.  Chance of precipitation is 50%.
Scattered
Showers
Lo 74 °F
Tuesday

Tuesday: Scattered showers.  Partly sunny, with a high near 84. East wind 10 to 15 mph.  Chance of precipitation is 50%.
Scattered
Showers
Hi 84 °F
Tuesday
Night
Tuesday Night: Scattered showers.  Mostly cloudy, with a low around 75. East northeast wind around 11 mph.  Chance of precipitation is 40%.
Scattered
Showers
Lo 75 °F
Wednesday

Wednesday: Scattered showers.  Partly sunny, with a high near 86. East wind 9 to 15 mph, with gusts as high as 20 mph.  Chance of precipitation is 50%.
Scattered
Showers
Hi 86 °F
Wednesday
Night
Wednesday Night: Isolated showers.  Partly cloudy, with a low around 75. East northeast wind around 10 mph.  Chance of precipitation is 20%.
Isolated
Showers
Lo 75 °F
Thursday

Thursday: Scattered showers, mainly before noon.  Mostly sunny, with a high near 85. Northeast wind 10 to 14 mph.  Chance of precipitation is 30%.
Scattered
Showers then
Mostly Sunny
Hi 85 °F
Thursday
Night
Thursday Night: Scattered showers.  Mostly cloudy, with a low around 75. North northeast wind around 9 mph.  Chance of precipitation is 30%.
Scattered
Showers
Lo 75 °F
Friday

Friday: Scattered showers.  Partly sunny, with a high near 85. North northeast wind 7 to 10 mph.  Chance of precipitation is 40%.
Scattered
Showers
Hi 85 °F

National Weather Service Forecast Details

 

GRLevel3 Radar

  [10/10
GRLevel3 radar from NWS station TJUA

Day 1 rainfall

Day 2 rainfall

Day 3 rainfall

521
FXCA62 TJSJ 090844
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
444 AM AST Mon Dec 9 2024

.SYNOPSIS...
Moderate east northeast winds will prevail today into Tuesday then
increasing while becoming more north northeast by Wednesday and the
rest of the workweek, as an induced surface trough develops east and
northeast of the area and surface high pressure builds north of the
region. Breezy conditions and pleasant temperatures and a mix of sunshine
and clouds will persist with an even drier trend by the middle of the
week. Choppy seas due to moderate to locally fresh winds are forecast
across the Atlantic and Caribbean waters through most of the week
with a small north to northwesterly swell forecast to spread across
the offshore Atlantic waters today through Tuesday.

&&

.SHORT TERM...Today through Wednesday...

Earlier in the night, as the axis of the surface trough was
positioned over the Mona Passage, Doppler radar detected strong
showers along the northern coastal waters of Puerto Rico and parts
of the Caribbean waters. Some of these showers moved across
southeastern Puerto Rico, with radar-estimated rainfall reaching up
to 0.70 inches in coastal areas of Maunabo. Currently, the trough
axis has continued moving westward and is now over eastern
Hispaniola, with shower activity diminishing for the most part.
However, some showers persist over the regional waters and are
expected to move across eastern portions of Puerto Rico and the
smaller islands through the morning hours. Minimum temperatures once
again ranged from the mid to upper 70s across coastal areas of
Puerto Rico and the USVI, and from the mid to upper 60s across
higher elevations and valleys of Puerto Rico.

The synoptic pattern for the remainder of the short-term forecast
period remains unchanged. Current GOES-16 infrared satellite data
indicates that the most active portion of the polar trough,
associated with the area of greatest divergence at upper levels, is
well northeast of the forecast area. Model guidance suggests that,
although a strong 250 mb jet will develop near the region, the
forecast area will remain under its subsidence side, with the
greatest divergence and diffluence pattern confined to areas farther
northeast as the TUTT deepens. This setup will limit widespread
convective activity across the region. Consequently, rainfall
coverage expected for the next few days has been slightly reduced.

However, surface-induced perturbations east of the Leeward Islands,
associated with the upper-level pattern, will occasionally stream
across the area. This will maintain moisture levels between the 50th
and 75th percentiles, which are near climatological normals for most
of the short-term period, with slightly lower values expected by
late Tuesday night. Under a northeasterly steering wind flow,
showery weather will affect windward sections of the islands during
the night and morning hours.

Additionally, certain low- to mid-level parameters will support
convection if sufficient lifting occurs. These include cold air
advection at mid-levels, which contributes to lower 1000-500 mb
thicknesses and steeper lapse rates between the 700-500 mb levels.
As a result, the combination of sufficient low-level moisture, sea
breeze convergence, and marginal instability could lead to
orographically driven convection each afternoon, particularly today.
Expect a limited to localized elevated flooding risk each afternoon,
mainly across interior and southwestern sections of Puerto Rico.

.LONG TERM...Thursday through Monday...

Latest model guidance remains persistent and continued to suggest
the amplified TUTT will linger just east of the northern Leeward
Islands while deepening through Friday along with a broad induced
surface trough which will slowly shift westwards across the area by
the weekend. This trough and possibly a weak surface low is forecast
to eventually lift northwards while spreading across the northeast
Caribbean and local region, as the TUTT lifts northwards into the
Central Atlantic. Models continue to suggest that the proximity of
this deepening and developing trough will aid in increasing
instability in the upper levels, resulting in more favorable
conditions for enhanced localized convective activity across the
area by the end of the period. Precipitable water values are still
expected to diminish and range between 1.60 to 0.95 through early
Friday. Thereafter and into the weekend moisture content rebounds
and values increase once again to near of slightly above normal 1.60
to 1.90 inches, as the broad surface trough spreads across the
region from the east.

During the early part of the period, moisture erosion and stable
condition aloft are expected as all guidance suggest we should
remain on the subsident side of the aforementioned upper trough.
This in turn should help to limit widespread convective activity
across the region. However by the weekend the pattern changes as the
trough spreads across the area, moisture will increase once again
and thus support much better potential for early morning and
afternoon convection. Widespread convection and significant weather
impacts are still not anticipated at this time but some localized
flooding will be possible, with the wettest period so far being
Saturday through Sunday due to the instability aloft and increasing
moisture content.

Mostly showery and an advective weather pattern can be expected at
times but mainly across the windward coastal areas during the
overnight night and early morning hours steered by moderate
northeasterly winds. This will be followed by limited convective
activity in the afternoons, primarily over the interior and
southwestern portions of Puerto Rico through at least Friday.
Thursday through Friday are forecast to be the driest days of the
period. As mentioned, a shift in this weather pattern remains
possible by the weekend and through the early part of the following
week, as low level moisture and instability increases due to the
developing of the surface-induced trough approaching the islands
from the northeast and a polar trough sweeping across the west
Atlantic. This will result in the best potential for showers and
isolated thunderstorm development across the islands and coastal
waters during the latter part of the period.

Seasonal northerly wind pattern will also bring very pleasant
temperatures across the area through the early part of the period,
with winds forecast to becoming more easterly by the end as now
suggested by model guidance. Occasional breezy conditions with an
occasional advective pattern of passing overnight and early morning
shower will be likely at times along the north and east coastal
areas but widespread and impactful rainfall accumulations are not
still not anticipated at this time.

&&

.AVIATION...
(06Z TAFS)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, brief mtn top obscr ovr E PR til
09/12Z. Also, SHRA with possible iso TSRA may develop in and around
TJPS btw 18z-22z. Sct mdt ocnly strong SHRA may move across the FA
with some reaching the windward side of the islands aft 09/22z. SFC
wnd light and variable to calm bcmg ENE 10-16 kts with some sea
breeze influences and ocnl hir gusts aft 09/14Z.

&&

.MARINE...
A surface high pressure spreading across the southwestern Atlantic,
will continue to promote a moderate east northeasterly wind flow across
the regional waters. The pressure gradient will tighten across the area
over the next few days promoting moderate to fresh winds. This pattern
will result in choppy seas across the Atlantic and Caribbean waters.
A small northerly to northwesterly swell will spread across the offshore
Atlantic waters today through Tuesday.

&&

.BEACH FORECAST...
A small north to northwesterly swell will impact the northern and
northwestern exposed beaches of the islands, potentially leading
to hazardous beach conditions in localized areas today through
Tuesday. However, the risk of rip currents will remain moderate
for most coastal areas of the islands. Increasing trade winds will
maintain choppy seas and hazardous beach conditions especially
along the north and east facing beaches by Wednesday.

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...None.
VI...None.
AM...None.
&&

$$

SHORT TERM...CVB
LONG TERM....RAM
AVIATION...CVB

NWS SJU Office Area Forecast Discussion

Saharan Air Layer

Wind Shear Tendency

Sea Surface Temperatures

Sea Surface Temperatures Anomalies

200hPa Velocity Potential Forecast