040
FXCA20 KWBC 151832
PMDCA

Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
232 PM EDT Wed Jul 15 2026

Forecast Bulletin 15 July 2026 at 1835 UTC:

Mexico...
Over the northwestern sector of Mexico, upper level troughing over
the Baja California Peninsula will interact with another upper
level trough over the south-central United States throughout the
day on Wednesday, amplifying the upper level divergence over the
Sierra Madre Occidental and the Altiplano regions. From the night
into early morning, expect thunderstorms and moderate to heavy
precipitation to accumulate on Wednesday into Thursday. The upper
level trough over the United States is inducing a low level trough
that extends into the Mexican Plateau, where moisture convergence
will persist and favor maxima of 20-35mm. On Thursday, the upper
closed low over the Baja California Peninsula is meandering
southwestward, away from the peninsula, giving way to the entry of
a strengthening ridge from the southwest United States. This new
system will interact with the upper level trough over the central
United States, favoring the divergent region over the northwest
sector of Mexico. Enhanced convection is expected with
precipitation maxima of 25-50mm. By Friday, northwest Mexico
continues to be the region with heavier precipitation as the
meandering upper level trough over the United States is perturbed
by the strengthening ridge over the west United States. As
additional tropical waves continue to propagate along the southern
Mexican Pacific coast, moisture is being channeled along the
continental coast in the Gulf of California, interacting with the
Sierra Madre Occidental. Over the central region of the country,
moisture is being advected along the Altiplano, increasing the
chance of moderate to heavy precipitation in northwest Mexico.

Central America...
On Wednesday, Central America will remain under the regimen of the
upper level trough that extends from the western Caribbean. A weak
ridging in the upper levels is developing to the east of this
trough, favoring the divergent sector over portions of Honduras
and Nicaragua, where a tropical wave is approaching from the
Caribbean Sea. In addition, the advection of moisture from the
Caribbean Low Level Jet (CLLJ) is interacting with the terrain,
favoring moisture convergence in this sector of the region, where
expect maxima of 30-60mm. Over the northern Central America
region, a passing tropical wave will favor light to moderate
precipitation on Wednesday, ranging from 20-40mm. By Thursday,
moisture convergence continues in the Caribbean coasts of Costa
Rica and Panama as the CLLJ remains present over the region,
enhanced by the increased low pressure over the East Pacific
Ocean. By Friday, drier conditions are expected over the northern
Central America region with the advection of dry air from the
Caribbean. The dry air associated with the Saharan Air Layer and
subsidence with the strengthening upper level ridge is finally
reaching this region, and a notable decrease in total
precipitation is indicating that they will be affected by this
drying pattern. Expect trace amounts from Nicaragua through
Panama, and light precipitation over the northern sector of
Central America.

North South America...
A generalized dry trend continues in much of the northeast sector
of the continent, while much of the higher amounts of available
moisture remain over the northwest sector. On Wednesday, the
residual moisture from a passing tropical wave converges along the
Andean regions in Colombia and western Colombia, favoring
generalized maxima of 20-40mm. Even though a tropical wave
propagates over the northern Guianas, the dry environment in its
surroundings will favor trace to light total precipitation over
the Atlantic coasts of the Guianas. On Thursday, a new tropical
wave enters the Guianas, while the other wave is expected over
eastern Venezuela bu the evening hours of Thursday. However, the
dry pattern is expected to continue with similar amounts over the
north and central sectors of tropical South America. The dry air
is advected into south Colombia, Ecuador, and north Peru, favoring
a decrease in total precipitation on Thursday. By Friday, the
waves are expected over the Lesser Antilles, and east Venezuela,
while the other wave is expected over the Lake Maracaibo region
and east Colombia, where these regions can expect light to
moderate totals of 15-30mm.

Caribbean and the Bahamas...
Most of the region is expected to remain under generally dry
conditions due to the continued advection of dry air by the
easterly trade winds, associated with the Saharan Air Layer. A
tropical wave is forecast to reach the eastern Caribbean on
Thursday, bringing a modest increase in low-level moisture and a
temporary weakening of the low- to mid-level trade wind inversion.
This will support the development of isolated showers, mainly
across the Lesser Antilles and the ABC Islands. Meanwhile, an
upper-level low currently located north of the Windward Islands is
expected to weaken while drifting northwestward. This will allow
an upper-level ridge and associated high pressure to build across
the Caribbean from Friday into Saturday. The strengthening ridge
will also become evident at the mid and lower levels of the
atmosphere. As high pressure builds east of the Caribbean, the
low- to mid-level inversion is expected to strengthen once again,
suppressing deep convection across the region. As a result, only
isolated light showers are anticipated, with precipitation
accumulations generally limited to trace amounts.

Tropical Waves Initialized at 12 UTC:
SOF INIT 16/00 16/12 17/00 17/12 18/00 18/12 19/00 19/12
17N 27W  30W  33W   37W   42W  47W  52W  57W  61W
17N 37W  41W  46W   51W   56W  61W  66W  70W  74W
18N 50W  54W  59W   63W   67W  71W  74W  76W  78W
16N 78W  81W  84W   88W   92W  96W  99W 102W 102W
20N 87W  90W  93W   96W   99W  ABS  ---
18N 96W  98W 100W  102W  104W 106W 108W 110W 112W

Luciano...(MDC)
Castellanos...(WPC)


$$