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FXCA20 KWBC 131945
PMDCA

Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
345 PM EDT Mon Apr 13 2026

Forecast Bulletin 13 April 2026 at 2000 UTC:

Across the Caribbean...

An upper level trough will be present across the eastern Greater
Antilles and will support upper diffluence and a jet streak max
across Hispaniola, Puerto Rico, the Virgin Islands, and the
northern windward islands for Monday and Tuesday. An upper level
jet streak max will be sustained along its base and exit region
and will favor divergence.  Mid-level temperatures will be below 8
degrees Celsius for Monday and Tuesday, leading to steeper lapse
rates and thus greater instability. The dynamic upper level
pattern will support the sustenance of an induced trough in the
region for the next three days. Currently, this trough has a
slanted axis and it has a central point near 67W. Ahead of the
trough axis, northeasterly low level winds will be converging into
Hispaniola and there will also be moist air advection, especially
through Monday evening. Meanwhile in Puerto Rico on Monday,
easterly and southeasterly low level winds will be dominant and
precipitable water values will approach 45mm. The aforementioned
conditions will yield elevated total precipitation maxima with a
risk for severe weather across the Dominican Republic and Puerto
Rico from Monday morning through Tuesday morning.

On Tuesday, the axis of the low level induced trough will be
moving across Puerto Rico and will arrive into the Dominican
Republic on Wednesday morning. However, precipitable water values
will decrease compared to the day prior. Behind the trough axis,
there will be easterly and southeasterly low level winds across
the northern Lesser Antilles, the Virgin Islands, and eastern
Puerto Rico, which will favor moisture convergence. Thus, expect
enhanced total precipitation maxima in the aforementioned regions
from Tuesday morning through Wednesday morning.

For Wednesday, there is model inconsistency in the eastward
propagation of the low level induced trough in the Greater
Antilles. The ECMWF slows down the propagation speed, with it
meandering between the Dominican Republic and Puerto Rico. The GFS
has it propagating across Hispaniola for the same time period and
it becomes less defined as it moves eastward.

With respect to precipitation impacts on Wednesday, light total
precipitation maxima will be possible across Hispaniola, but if
the low level trough trends towards the GFS position, there will
be greater moisture convergence that will yield moderate total
precipitation maxima. The environment will still be unstable
across Hispaniola and Puerto Rico for Wednesday as well. In Puerto
Rico and the Virgin Islands, more easterly low level winds will
dominate on Wednesday, yielding moderate total precipitation
maxima.

In Tropical South America...

A broad mid-to-upper level ridge is located across Bolivia and
Brasil and it will be supporting easterly low level winds into the
interior of the Amazon Basin for the next three days. It will
briefly lose its organization on Tuesday and will reorganize
across north-central Brasil on Wednesday. This feature will favor
upper diffluence, which will sustain upper divergence. This
mid-to-upper level pattern will support the transport of moist air
from the Atlantic into the Amazon Basin. With respect to
precipitation, there will be a series of low level troughs that
will be traversing the basin and they will enhance moisture
convergence. These features will yield moderate total
precipitation maxima.

Meanwhile across the Amazon Delta and northeast Brasil, upper
diffluence will also be present for the next three days, favoring
upper divergence. By Wednesday night, an upper level trough will
be moving into the region from the south and it will also support
upper divergence. Also, the moisture plume associated with the
Intertropical Convergence Zone (ITCZ) will be converging into the
area. Thus, expect daily moderate total precipitation maxima for
the next three days.

Along the Pacific coasts of Colombia, Ecuador, and Peru, a low
level trough will be present for the next three days, supporting
cyclonic rotation. Precipitable water values will also be
elevated. Note that there will be a trend in more widespread
convection as the divergent phase of the MJO will be moving into
the region, particularly after Tuesday. This will lead to higher
total precipitation maxima across a greater area.

Across Central America and Mexico...

Easterly low level winds will prevail across Costa Rica and Panama
and lead to moisture pooling along the coasts. This will enhance
moisture convergence and support moderate total precipitation
maxima for the next three days.

Meanwhile in northern Mexico, an upper level trough will be moving
into the continent on Monday and its axis will arrive into
northwest Mexico on Tuesday. Thereafter, there will be an
intensifying upper jet streak max across northern Mexico that will
sustain upper divergence for Tuesday. At the low levels, expect
the increase in southerly and southeasterly low level winds into
northeast Mexico, which will support moist air advection. Thus,
moderate total precipitation maxima is likely in northeast Mexico
for Tuesday.


Tinoco-Morales...(WPC)


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