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: 7:32 pm AST Jul 20, 2024

Hazardous Weather Outlook
Overnight

Overnight: Isolated showers.  Widespread haze. Partly cloudy, with a low around 80. East wind around 7 mph.  Chance of precipitation is 10%.
Isolated
Showers

Lo 80 °F
Sunday

Sunday: Isolated showers before noon, then isolated showers after 3pm.  Widespread haze. Mostly sunny, with a high near 89. Heat index values as high as 103. East northeast wind 10 to 16 mph, with gusts as high as 21 mph.  Chance of precipitation is 20%.
Isolated
Showers

Hi 89 °F
Sunday
Night
Sunday Night: Scattered showers, mainly after midnight.  Increasing clouds, with a low around 78. East wind 8 to 11 mph.  Chance of precipitation is 50%.
Isolated
Showers then
Scattered
Showers
Lo 78 °F
Monday

Monday: Showers likely, mainly before noon.  Mostly cloudy, with a high near 88. East wind 10 to 14 mph.  Chance of precipitation is 60%.
Showers
Likely

Hi 88 °F
Monday
Night
Monday Night: Scattered showers.  Mostly cloudy, with a low around 78. East wind around 10 mph.  Chance of precipitation is 50%.
Scattered
Showers

Lo 78 °F
Tuesday

Tuesday: Isolated showers.  Mostly sunny, with a high near 90. East wind 11 to 16 mph, with gusts as high as 21 mph.  Chance of precipitation is 20%.
Isolated
Showers

Hi 90 °F
Tuesday
Night
Tuesday Night: Mostly clear, with a low around 78. East wind 9 to 11 mph.
Mostly Clear

Lo 78 °F
Wednesday

Wednesday: Scattered showers.  Mostly sunny, with a high near 91. East wind 13 to 16 mph, with gusts as high as 21 mph.  Chance of precipitation is 50%.
Scattered
Showers

Hi 91 °F
Wednesday
Night
Wednesday Night: Clear, with a low around 78. East wind 9 to 11 mph.
Clear

Lo 78 °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

331
FXCA62 TJSJ 202124
AFDSJU

Area Forecast Discussion
National Weather Service San Juan PR
524 PM AST Sat Jul 20 2024

.SYNOPSIS...

A big pulse of Saharan Dust Air Layer will continue to promote
hazy skies tonight through Sunday afternoon and a warm weather
pattern across the region. A surface high pressure centered north
of the islands will maintain breezy winds throughout the weekend.
By early next week, some moisture will filter into the forecast
area resulting in showers and thunderstorms possible.

&&

.SHORT TERM...Tonight through Monday...

During the morning hours, partly cloudy skies prevailed with some
showers across eastern and southeastern sectors. The Doppler
radar estimated less than half an inch of accumulation across most
areas. Additional showers developed in the early afternoon across
northwest Puerto Rico leaving about three-quarters of an inch.
Winds have been mainly from the east around 15 to 20 knots, with
gusts up to 25 knots. Maximum temperatures were from the upper 80s
to mid-90s across coastal areas to the mid-70s across the higher
elevations. Heat indices between 100F-115F were observed across
coastal areas and lower elevations where A Heat Advisory was in
effect until 5 PM AST. San Juan tied its previous record high
temperature of 92 degrees, set in 1995. In the U.S. Virgin
Islands, daytime highs ranged from 88 to 94 degrees, with heat
indices soaring into the lower 110s in Saint Croix.

A surface high pressure centered north of the islands will maintain
breezy winds throughout the weekend. The tropical wave is already
outside our area, allowing the entry of much drier air along with
Saharan Dust promoting hazy skies. This particulate will last
into tomorrow exacerbating health conditions for vulnerable
populations and those sensitive to air quality issues, then
gradually clearing out in the afternoon hours. Tonight, expect
limited shower activity as that drier airmass dominates. This
airmass has below-normal precipitable water values of around 1.4
inches. Similar conditions should continue tomorrow, with no to
limited shower activity.

By Monday, some moisture will filter into the forecast area and
precipitable water values should increase again to above normal,
with showers and thunderstorms likely once again. Morning
activity will be favored across eastern Puerto Rico and the Virgin
Islands, while showers and thunderstorms are possible across the
interior and western PR during the afternoon hours. As a result,
the risk for urban and small stream flooding will be elevated
early next week.

&&

.LONG TERM...Tuesday through Saturday...
.PREV DISCUSSION... /issued 455 AM AST Sat Jul 20 2024/

A seasonal pattern will be in place for the beginning of the long
term. At the surface, broad high pressure will dominate the Atlantic
Basin, including the Caribbean, resulting in easterly winds across
the region. Embedded in the wind flow, patches of shallow moisture,
with PWAT around 1.7 to 2 inches, will move in and out of the area
from Tuesday through Wednesday. Under this pattern, the islands will
primarily experience the typical weather pattern with variable
mornings between warm conditions and some isolated showers, followed
by afternoon convection over the western interior sections of Puerto
Rico. From late Wednesday into early Thursday, a slot of drier
airmass will move in but not last long, as a wind surge reaches the
islands, increasing the sustained surface winds and the potential
for shower development. Combining the wet pattern on Thursday, model
guidance indicates some instability provided by the divergence side
of an upper-level trough of an upper-low just over the western
Atlantic. The outcome will be a more favorable scenario for more
widespread shower activity. However, given the windy conditions,
fast-moving showers might not accumulate significant rainfall in
most areas.

After that wind surge, the NASA Goddard Earth Observing System Model
V5 suggests another round of a Saharan Dust event. Similar to the
past week`s event, this will be moderate, with optical depth
concentration between 0.2-0.3. This pattern will erode most
available moisture, limiting the shower activity. For the same
period, the dominant feature will be the surface high pressure just
over the Central Atlantic, resulting in an east-southeasterly wind
flow. As usual during the summer days in Puerto Rico and the U.S.
Virgin Islands, warmer conditions with Saharan Dust particles will
increase heat index values across the region. Excessive heat
products are forecasted for those days.

&&

.AVIATION...

(18Z TAFs)

Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. HZ due to Saharan dust may lower VSBY near
6 miles thru 21/14z across the area terminals. East winds will
continue at 15-20 kt with higher gusts across coastal areas, but
bcmg lighter after 21/02z.

&&

.MARINE...

A broad surface high pressure over the Central Atlantic will continue
to promote moderate to locally fresh easterly winds across the local
waters through early next week, resulting in choppy seas. Small craft
advisories will remain in effect until 6 PM this evening, then Small
craft should continue to exercise caution across most marine zones.
A trade wind perturbation will arrive by Monday, increasing the
potential for showers and thunderstorms across the local waters.

&&

.BEACH FORECAST...

A surface high pressure over the Central Atlantic will promote
breezy conditions across the coastal areas of the islands through
the weekend. There is a high risk of rip currents for St. Croix
beaches through this afternoon, then a moderate risk of rip
currents should be present across most beaches for the next few
days. For more details about the latest forecast, please refer to
the Surf Zone Forecast (SRFSJU).

&&

.SJU WATCHES/WARNINGS/ADVISORIES...

PR...None.

VI...High Rip Current Risk until 6 PM AST this evening for VIZ002.

AM...Small Craft Advisory until 6 PM AST this evening for AMZ711-712-
     716-723-733-741.

&&

$$

SHORT TERM...YZR/RAM
AVIATION...DSR/RAM
LONG TERM....LIS
PUBLIC...CVB

NWS SJU Office Area Forecast Discussion

Saharan Air Layer

Wind Shear Tendency

Sea Surface Temperatures

Sea Surface Temperatures Anomalies

200hPa Velocity Potential Forecast