Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
249 PM EST Mon Jan 12 2026

Forecast Bulletin 12 January 2026 at 1950 UTC:

Over the forecast region, the CFS model is suggesting the presence
of divergent conditions in the upper levels, with the potential
for Rossby Wave presence and an atmospheric kelvin wave-like
pattern in the forecast region. These conditions are expected to
continue for the forecast period and could enhance heavy
precipitation locally.

A cold frontal boundary is located from the central Atlantic Ocean
and enters the north Bahamas, into north Cuba, entering Mexico
through the Yucatan Peninsula, where is expected to become
stationary along the Sierra Madre Oriental and weaken by Veracruz
and Tamaulipas by Monday evening. A mid-level ridge is centered
over north Central America, and extends into south Mexico and into
the west Caribbean, favoring subsidence and trade wind cap
inversions over south Mexico into Central America on Monday. To
the north, a short wave trough in the mid to upper levels is
located over Northwest Mexico, enhancing some divergence over the
north and central regions of Mexico. However, due to the lack of
significant moisture in the region, expect light precipitation
totals from Chihuahua to north Sinaloa/Durango on Monday. In
southern Veracruz, the presence of the nortes winds from the
frontal boundary, continues to activate the Tehuantepecer Low
Level Jet (LLJ), favoring localized cyclonic circulation in the
lower levels in southern Veracruz and west Tabasco, reaching into
portions of northwest Chiapas. This onshore flow will favor
enhanced moisture to converge along the terrain and precipitation
maxima of 30-60mm are expected, with localized higher totals
possible. On Tuesday, an upper level ridge strengthens over south
Mexico and extends into the west Caribbean, while the mid-level
ridge continues to meander over the region. This will help in
weakening the frontal boundary over Mexico and the north
Caribbean, while the portion of the front located over the Bahamas
will receive some upper level support from the strengthening jet
stream extending from Mexico into the southern United States,
maintaining the front over the region due to the divergence from
the jet stream. Although these conditions are present, the low
amount of moisture in the region will help keep precipitation
totals light over most of the north Caribbean and from Mexico into
Central America. However, conditions begin to change on Wednesday
when a polar trough enters into the south-central United States,
enhancing the upper level jet stream, and the base of the trough
interacts with the upper level ridge over Mexico and Central
America. This will help weaken the ridge in the mid levels as
well, and favor the presence of a frontal boundary from the
eastern seaboard of the United States into north Bahamas, Cuba and
into the Yucatan Peninsula. In addition to the frontal boundary, a
weak shear line forms over west Cuba and extends into north
Honduras, where expect enhanced moisture convergence and
precipitation totals of 30-60mm, with a potential of higher
amounts possible. West-central Cuba can expect maxima of 20-35mm,
while the north Bahamas can expect maxima of 15-20mm with a
marginal risk of severe weather. South Veracruz/west Tabasco can
expect maxima of 20-45mm.

The other region of interest is northwest South America, where the
presence of the Panamanian trough over Panama extends to north
Ecuador, favoring moist onshore flow from the east Pacific from
the Choco region into the Gulf of Guayaquil on Monday. With the
enhanced upper level divergence, expect maxima of 20-45mm with
localized higher amounts. To the east, moisture is pooling over
the western Amazon Basin, impacted by the upper level divergence
over the region, as an upper level trough extends into Colombia,
and interacts with a weak Bolivian high that extends into north
Peru. The west Amazon Basin can expect maxima of 20-45mm with
localized higher amounts. On Tuesday, the moist onshore flow
continues into south Colombia into north Ecuador, favoring maxima
of 30-60mm in the region. Over the Amazon Basin, troughs in the
lower levels are propagating along the trade winds, impacted by
diurnal heating processes and favoring precipitation in the
afternoon hours on Tuesday. As these interact with the mountain
regions from south Colombia into north Peru, expect maxima of
20-45mm. On Wednesday, similar conditions are expected over the
region, and thus similar amounts could be seen in the
aforementioned regions. A difference is that an upper level system
over the Amazon Basin is retrograding over the area, interacting
with the upper level trough over Colombia, and assisting with
retrograding that system to the north on Wednesday and into
Thursday. This will help favor a slight reorientation of the
Panamanian trough over Panama, and favor moist onshore into the
central portion of the country. They can expect maxima of 20-35mm.

Castellanos...(WPC)