Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
925 AM EDT Fri Oct 31 2025

Forecast Bulletin 31 October 2025 at 1700 UTC:


In Mexico...

A dynamic upper level pattern will be present across the gulf
states for the forecast cycle, where a positively tilted upper
level trough may help drive an increase in upper divergence across
its base and exit region. At the surface, a cold front will begin
to develop during the day on Saturday across Texas and will
rapidly move southward. By Saturday evening, the cold front will
be located across the Texas - northern Mexico border. This front
will extend into southern Tamaulipas and northern Veracruz by
Sunday evening. Precipitation chances are expected to increase
with the arrival of this cold front. Through the day on Saturday,
expect an increase in low level southerly winds that will help
transport moist tropical air into the region. A change in the wind
direction is expected as the front begins to gain definition and
propagate southward. Moisture convergence will be present along
and ahead of the cold front. Moderate rainfall accumulations are
possible across Tamaulipas on Saturday, where isolated total
precipitation maxima of 10mm is possible. By Sunday, there will be
an increase in precipitable water across southern Veracruz, where
values of 38mm or greater is probable. Thus, higher precipitation
accumulations are expected for Sunday across southern Veracruz and
Chiapas. Elsewhere in Mexico, low level troughs will continue to
promote moisture convergence and may increase precipitation
chances. If any precipitation does develop, expect it to be
influenced primarily by the diurnal cycle and local effects.

In the Greater Antilles and Central America...

The presence of a pre-existing frontal system and its interaction
with a low level induced trough will enhance moisture convergence
significantly across parts of Nicaragua, Honduras, Jamaica, and
Cuba throughout the forecast cycle. This frontal system will be
primarily stationary on Friday evening and will be located across
the southeastern Bahamas, Cuba, and Honduras. It will begin to
transition into a warm front on Saturday across the Bahamas and
Cuba while an induced low-level trough will be located directly to
its southeast. This frontal system will lose its definition after
Sunday.

The mid-to-upper level regime will drive the dynamic nature of the
low levels and surface for the forecast cycle. In the upper
levels, a weakening trough will continue to move westward across
the Caribbean basin before losing definition on Sunday due to its
interaction with another upper level trough that is extending from
the mid-latitudes. This mid-latitude upper trough is anticipated
to have its base and exit region spanning across the Yucatan
Peninsula, Cuba, and the northern Bahamas on Saturday and Sunday
and may promote upper divergence in this region. Precipitable
water values will exceed 50mm in the region where the
aforementioned frontal system and induced low level trough will
interact. Expect the low level wind direction to be from the
northeast prior to the arrival of the low level induced trough on
Saturday across Costa Rica. On Friday, the areas with the greatest
chance for precipitation accumulations will be along the
stationary front and Caribbean coasts of Costa Rica and Panama.
Note, chances for precipitation will increase across Jamaica,
Cuba, and the southeastern Bahamas on Friday evening with the
arrival of the axis of the aforementioned low level induced
trough, though accumulations will remain on the moderate side. On
Saturday, the low level wind direction will begin to shift to a
more easterly direction across the northern regions of Costa Rica
while in Nicaragua, the low level wind flow will remain from the
northeast. Regardless of the difference in wind direction in these
two areas, enhanced moisture convergence is highly probable and
high precipitable accumulations are likely for Saturday and
Sunday. Though precipitable water values are expected to decrease
across the northern regions of Caribbean Sea Basin for Sunday, the
upper levels will help increase the chances for convective
initiation across Honduras and northern Nicaragua.

Another feature of interest is an incoming tropical wave that is
anticipated to move across the eastern Caribbean Sea Basin for the
next three days. Along and behind its axis, expect increased
moisture convergence and vertical ascent to promote precipitation.
On Friday, the area with the greatest precipitation chances will
be the leeward islands of the Lesser Antilles. By Saturday, expect
the area of greatest precipitation chances to be across Puerto
Rico and the Dominican Republic. The tropical wave will be
absorbed by a mid-level ridge to the northeast on Saturday but its
moisture field will continue to propagate across the region. By
Sunday, the remnant moisture will be moving into Jamaica and
southeast Cuba. For all three days, local effects, the diurnal
cycle, and orographic enhancement may yield moderate total
precipitation maxima.

In Panama and tropical South America...

The presence of the tropical wave across the Caribbean Sea will
have an indirect effect across the Pacific coasts of Panama,
Colombia, and Ecuador, where long fetch low level westerly winds
may begin to dominate the wind regime. This will enhance moisture
convergence across this sector. Prior to the arrival of this
tropical wave, moisture will be abundant in this region but the
wind flow will be weak. Thus, if any convection does develop on
Friday and Saturday, it will be mostly driven by local effects and
the diurnal cycle. The presence of the upper level trough across
the Caribbean Basin may enhance some upper divergence across the
southern regions of central America and northern Colombia and
Venezuela until Saturday, providing additional upper level
support.

Across tropical South America, seasonal conditions will persist
through the forecast cycle. Ridging will be present in the upper
and mid levels, limiting the potential for deep convection despite
there being moisture in the western portions of the Amazon Basin.
Thus, if any convection does develop, it will likely be attributed
to the presence of surface to low level troughs, local effects,
and the diurnal cycle. Orographically enhanced precipitation is
also expected through the forecast period.


Positions of Tropical/Easterly Waves Initialized at 12 UTC
TYP SOF  INIT  31/00  31/12  01/00  01/12  02/00  02/12  03/00
TW  16N   58W   62W    66W    69W    72W    --     --     --    

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

Tinoco-Morales...(WPC)