162
FXCA20 KWBC 161836
PMDCA

Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
236 PM EDT Thu Jul 16 2026

Forecast Bulletin 16 July 2026 at 1835 UTC:

Mexico...
On Thursday, the two upper level troughs over the southern United
States and the Baja California Peninsula are joining into a larger
system throughout the day.By the evening hours, the area of
enhanced divergence is expected over Texas and into Coahuila,
where moisture enters from the south fueling light precipitation
in the Mexican Altiplano, with a potential for locally heavier
precipitation on Thursday into Friday. Another area of enhanced
divergence is expected in the southern extent of the upper trough
over the Baja California Peninsula, located over the Sierra Madre
Occidental, where expect moderate precipitation totals of 20-40mm.
To the south, two tropical waves are propagating over Mexico, one
over southwest Mexico, and another over the Gulf of Tehuantepec,
extending into the monsoon trough over the east Pacific. Enhanced
moisture convergence over the lower Sierra Madre Oriental will
favor maxima of 25-50mm. Elsewhere, expect light precipitation
totals on Thursday. On Friday, a reorganization of the upper level
systems, enhanced by the increase circulation associated with
Tropical Storm Elida, will weaken the areas of divergence aloft
over Mexico, limiting the locations of moderate precipitation to
the Sierra Madre Occidental. At this time, the two tropical waves
propagating over the southern Mexico region are approaching each
other over the Eastern Pacific Ocean, further advancing the
circulation in the area. By Saturday, the tropical wave south of
the Baja California Peninsula will absorb the tropical wave that
was approaching from the east, favoring a closed area of
circulation over the monsoon trough. As these waves are in the
region, available moisture is being fed into the continental west
coast of Mexico, continuing to favor moderate to locally heavy
precipitation along the Sierra Madre Occidental and into the
western Eje Volcanico Transversal, where the heaviest
precipitation is expected in Mexico on Saturday.

Caribbean and The Bahamas...
Most of the region will continue to experience predominantly dry
conditions due to the advection of dry air by the easterly trade
winds associated with the Saharan Air Layer . A tropical wave
currently moving across the eastern Caribbean is expected to reach
Hispaniola by late Friday. Despite the presence of dry air in the
lower and middle levels of the atmosphere, pockets of shallow
moisture may support the development of isolated showers, mainly
across the Greater Antilles from Friday into Saturday with the
passage of the aforementioned tropical wave. An upper-level
low-pressure system located north of the Lesser Antilles, along
with another upper-level low over Suriname and an associated
trough extending across the Caribbean, will gradually shift
westward. This will allow the Atlantic high-pressure system and
its associated ridge to expand across the Caribbean by Friday. As
the Atlantic high-pressure system strengthens, the trade wind
inversion is expected to become more pronounced in the lower
levels of the atmosphere, suppressing deep convective development
across the Lesser Antilles and the Windward Islands. The
strengthening Atlantic high-pressure system will be the dominant
synoptic feature responsible for tightening the pressure gradient
across the Caribbean from Friday into Saturday, resulting in fresh
to strong easterly trade winds, particularly over the southern
Caribbean Sea and north of La Guajira. Another tropical wave is
expected to enter the eastern Caribbean on Saturday. However,
given the prevailing dry and stable atmospheric conditions,
precipitation accumulations are expected to remain generally
limited to trace amounts, with overall dry weather prevailing
across much of the basin.

Central America...
Over the next three days, the day with the heaviest precipitation
in the region will be on Thursday, with the presence of tropical
wave over land and the Caribbean Low Level Jet (CLLJ) favoring
moisture convergence, primarily in Guatemala and Belize, and in
Costa Rica. In the northern Central America sector, the base of an
upper trough will favor some weak divergence through the evening
and overnight hours, however, the system is expected to
restructure into the early hours of Friday as it interacts with a
ridging pattern over the Caribbeans. By Friday morning, dry air
associated with the Saharan Air Layer enters Central America,
beginning a dry trend. In the southern sector, high amounts of
moisture remain, but any deep convection is limited due to the
entry of trade wind inversions and a dry mid level. Expect
moderate precipitation of 15-30mm in Costa Rica and Panama, and
lower totals to the north on Friday. By Saturday, the dry air in
the mid levels extends to the entire region of Central America,
enhancing the trade wind inversions and inhibit deep convection
for much of the region. Expect light precipitation totals
throughout on Saturday.

North South America...
The northern South America region will see a similar drying trend
as Central America. The passing of tropical waves to the north
will assist with the advection of moisture reaching the northwest,
and the interaction with the Andes Mountains will favor moisture
convergence and orographic lift, fueling convection primarily from
Colombia into northern Ecuador and Peru. The Inter-tropical
Convergence Zone (ITCZ) is positioning over the northern coast of
Guyana and will meander north into Trinidad and Tobago over the
next three days. The placement of the ITCZ will amplify convection
in the region, giving way for light to moderate precipitation
totals daily over the next three days. Ridging over the northern
portion of the continent will continue to favor subsidence over
the next three days, as it meanders west ward from east Brasil
into the Amazon Basin.

Tropical Waves Initialized at 12 UTC:
SOF INIT 17/00 17/12 18/00 18/12 19/00 19/12 20/00 20/12
19N 33W  38W  43W   48W  52W  57W  62W 67W 72W
19N 46W  52W  57W   62W  67W  71W  74W DISS ---
20N 59W  63W  67W   70W  73W  76W  79W 82W 85W
18N 83W  86W  88W   90W  93W  96W  99W 102W 103W
20N 93W  96W  99W  102W 104W  ABS  ---
19N 100W 103W 105W 107W 109W 110W 112W 114W 116W

Note: Due to the GOES-19 outage, the initialization for the
tropical waves may be misaligned. Some errors may be present in
the wave tracking for Thursday.

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


$$