Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
301 PM EDT Thu Apr 09 2026

Forecast Bulletin 09 April 2026 at 1905 UTC:

Mexico and North Central America...
An upper level zonal flow is expected to continue over much of the
region on Thursday and continuing on Friday, with the presence of
embedded short wave troughs progressively making their way over
much of Mexico over the first two days. These shortwave troughs
favor weak divergent conditions aloft, but because of the
progressive pattern, they are not expected to produce heavy
precipitation in the region. By Saturday, an upper level trough
enters the western United States, with its base reaching south of
the Baja California Peninsula in the Eastern Pacific, interacting
with a ridging pattern to its east. Enhanced upper level
divergence is expected downstream, over north and central Mexico
throughout the day on Saturday and into Sunday morning. In the
lower levels of the atmosphere, moist south and easterly winds
enter the eastern regions along Mexico, and much of north Central
America, favoring weak orographic lift along the Sierra Madre
Oriental region and the mountainous regions in the Continental
Divide. On Thursday and Friday, expect the strongest moisture
convergence to be enhanced along the Sierra Madre Oriental, where
light to moderate amounts of precipitation are expected. By
Saturday, the presence of an upper trough to the north will favor
a sharp decrease in pressures in the north and central United
States, favoring the development of a strengthened Low Level Jet
over east Mexico. This will advect moisture along the Sierra Madre
Oriental region, extending into the Altiplano regions of
north-central Mexico, where expect moderate to heavy precipitation
on Saturday. Expect a slight risk of severe weather over portions
of north Coahuila, Nuevo Leon, and Tamaulipas.

Caribbean and the Bahamas...
On Thursday, a generalized ridging is present over much of the
Caribbean Sea region, with a disorganized ridge in the mid-levels.
This ridging will favor a subsident environment, where trade wind
inversion caps will inhibit the development of strong convection
over much of Greater and Lesser Antilles. However, an upper level
trough over the Bahamas has favored the presence of a frontal
boundary that extends from the Central Atlantic and into the
northern Bahamas throughout the day on Thursday. Into Friday, the
frontal boundary meanders southward into the southern
Bahamas/Turks and Caicos and into northern Cuba as a stationary
front. A weak shear line/prefrontal trough develops over
Hispaniola from Friday evening into early Saturday morning.  The
frontal boundary continues its eastward trajectory over the
Central Atlantic, but continues to weaken over the northern
Caribbean by the evening hours. A prefrontal trough continues over
Hispaniola, favoring the precipitation into the later hours of
Saturday and early morning on Sunday. Ahead of the front, along
the Lesser Antilles, expect troughing in the low levels to favor
some lift, with available moisture exceeding 40mm. Light
precipitation totals are expected on Sunday.

North South America and Southern Central America...
The Bolivian High over central South America is a potent system
that extends its periphery into Northwest South America on
Thursday and it is expected to continue to do so throughout the
next three days. This will be important for upper level support
because it will interact with the ridging to the northeast giving
way to amplified diffluence aloft, particularly over the West
Amazon Basin and Colombia. In the lower levels, various
propagating low level troughs are expected to affect the region
over the next three days. Over the west Amazon and into western
Colombia, expect a trough to propagate over the region on
Thursday, favoring deep convection by the early morning hours of
Friday. The eastern portions of Panama are expected to see some of
the effects of this trough, while the Caribbean Low Level Jet
supports the onshore flow into the coasts of Panama. On Friday,
the propagating trough is meandering over the Gulf of Panama
region with increased moisture and strong winds from the Caribbean
LLJ. The cyclonic circulation associated with this system reaches
the western shores of Colombia, where expect light to moderate
amounts of precipitation. Over the Western and Central Amazon
Basin, continuous moist easterly flow enters the region, where
expect troughing in the lower levels to assist with lift and
enhanced moisture convergence. With the periphery of the Bolivian
High providing divergent upper level support, expect moderate to
heavy precipitation over much of the region on Friday. By
Saturday, a propagating trough enters the West Amazon Basin, and
enhanced upper level divergence is present over the same region
due to a structural change in the Bolivian High elongating over
much of the central portions of the South American continent.
Expect moderate precipitation maxima on Saturday over much of the
region.

Castellanos...(WPC)