019
FXCA20 KWBC 011700
PMDCA

Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
1200 PM EST Mon Dec 01 2025

Forecast Bulletin 01 December 2025 at 1700 UTC:

In the Lesser Antilles, a potent upper level trough, that is
reflected in the mid and low levels, currently has an axis across
Hispaniola and will continue migrating southeastward into the
Lesser Antilles by late Tuesday. Expect the development of a low
level induced trough east of the windward islands starting
Tuesday. By ealy Wednesday morning, the axis of the induced trough
will begin to move across the islands. It will be accompanied by
precipitable water totals in excess of 50mm. Upper divergence will
also be present across this region and mid-level shortwave troughs
will enable the enhancement in vertical ascent. Thus, a total
precipitation maxima of 15 - 30mm is expected from Tuesday morning
through Wednesday morning and increasing to 30 - 60mm from
Wednesday morning through Thursday morning between Saint Lucia and
Trinidad and Tobago. Another feature of interest is a westward
propagating low level trough that currently has an axis near
61.5W. There will be a subtle increase in moisture across the
leeward islands starting Monday afternoon. By Tuesday evening, the
axis of the trough will be located over Puerto Rico and will begin
to lose definition thereafter. On Wednesday evening, the trough
will be across Hispaniola. Local effects and the diurnal cycle may
promote the development of showers in these regions for the next
three days. Expect a subtle enhancement in moisture convergence,
especially in areas with orography.

Across Mexico, a potent upper trough across the interior of the
United States and accompanying strong jet streak max will favor
the sustenance of a surface cold front that will be moving across
the aforementioned regions on Monday and Tuesday. Note that there
is also a potent upper ridge located across the northern Gulf,
which will prohibit the southward movement of the front into
Central America and the Greater Antilles. Hence, the frontal
systems will mostly impact the far northern regions of the domain.
On Monday evening, the cold front will extend into southern
Tamaulipas and along the Oriental Sierra Madre. A stationary front
will extend across Nuevo Leon and Coahuila. Minimal precipitation
impacts are expected for Monday as there will be limited moisture
and moisture convergence in this area. By Tuesday, the cold front
will begin to transition into a decaying stationary front and will
be located across northern Veracruz. There will be a subtle
increase in moisture in this region as well as a brief window of
onshore low level wind flow on Tuesday evening. The low level wind
direction will quickly shift to a more southerly component early
Wednesday morning. Thus, the greatest chances for precipitation
will be Tuesday evening and accumulations will range from 15 -
30mm for northern Veracruz.

Another region of interest in Mexico is northern Sinaloa and
Durango for Wednesday. A mid-level shortwave trough is anticipated
to propagate across the region late Wednesday into Thursday. This
will help increase precipitation chances as it will promote
vertical ascent and there will be a general increase in available
moisture in the region. Currently, there is model discrepancy in
arrival of a mid-level shortwave trough and the magnitude of the
low level onshore flow. If the shortwave trough arrives later,
then the chance for precipitation will be delayed for after
Thursday morning.

Across Central America, the presence of the monsoon trough and the
Panamanian trough will continue to drive convective processes
across Costa Rica and Panama through the next three days. There
will be a decrease in precipitable water with passing days in the
area and a general decrease in precipitation accumulations. Across
the Darien Gap and Colombia, An upper level diffluent pattern will
dominate across the area through the forecast cycle and this will
help enhance upper divergence. In the low-levels, there will be
abundant precipitable water present. Across central Colombia,
expect northerly low level wind flow to interact with the local
topography and favor precipitation accumulations of 30 - 60mm from
Monday morning through Tuesday morning. By Tuesday, similar
conditions will prevail. A decrease in precipitable water and low
level wind speeds will limit accumulations for Wednesday.
Elsewhere in tropical South America, a series of low level troughs
will increase moisture convergence across the region, leading to
an increase in precipitation chances. The diurnal cycle and local
effects will be the main drivers for the initiation of
precipitation. An area of interest is Brasil, where upper level
speed divergence will favor the sustenance for deep convection in
the area of the next three days. Daily total precipitiaotn maxima
will exceed 40mm in central Brasil. Otherwise, seasonal conditions
will continue for the rest of the region.


Positions of Tropical/Easterly Waves Initialized at 12 UTC
TYP SOF  INIT  02/00  02/12  03/00  03/12  04/00  04/12  04/00
--  --    --    ---    ---    ---    ---    ---    ---    ---

For the latest available charts please visit:
https://www.wpc.ncep.noaa.gov/international/crb_day1-3.shtml

Tinoco-Morales...(WPC)
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