519
FXCA20 KWBC 121857
PMDCA

Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
257 PM EDT Wed Aug 12 2026

Forecast Bulletin 12 August 2026 at 1900 UTC:

Broad areas of significant rainfall accumulation are expected
across Orinoquia into southern Central America, Hispaniola to
Cuba, and Northern Central America to Southwestern Mexico,
throughout the next three days associated with the passage of a
series of tropical waves. More isolated sectors of convective
precipitation are forecasted over northwest Mexico due to the
Mexican North American Monsoon.

Mexico and Northern Central America . . .
Two upper-level troughs, one over Sierra Madre Oriental and
another over the southern Gulf into the eastern central Pacific
basin, will dynamically support ascending motion across central to
southwestern and southeastern Mexico. A mid level trough is
extended along southwestern Guatemala into the Gulf enhancing
precipitable water (PWAT) around the region while interacting with
a tropical wave entering the Peninsula. This pattern will drive
rainfall maxima of 15-35 mm across the region today. Over Sierra
Madre Occidental moderate to significant rainfall is expected,
linked to the day heating and the North American monsoonal setup.
Throughout the next few days, the upper-level cut-off low will
move into northeastern Mexico. It will get better structured and
will support convection, increasing shower accumulation over
central, south and eastern sectors. Meanwhile, a plume of Saharan
dust will move in and dry things out over southeastern Mexico and
northern Central America. A couple of mid level short waves will
move across Oaxaca into west Mexico bearing regions of well above
normal PWAT values and significant rainfall along the coast.

The Bahamas and Caribbean . . .
An upper-to-mid-level trough is located along southern Bahamas
into eastern Cuba supporting dynamical upward motion over portions
of Hispaniola while interacting with a tropical wave beneath. A
second short wave in the mid level extends its axis over the Mona
passage and a second tropical wave over Lesser Antilles helps to
enhance PWAT from Puerto Rico to the eastern Caribbean. This set
up will be the major trigger for showers in the region throughout
the next three days. The upper-level trough will be cut off and
remain centered over Haiti to eastern Cuba, increasing upper
diffluence over this region. In the lower-levels, both shortwave
troughs will propagate westward bringing an increase in rainfall,
with accumulation of 15-35 mm likely over eastern Cuba and
Hispaniola on Thursday and over central Cuba by Friday.

Northern South America and Southern Central America . . .
A lower-level trough extended from the Gulf of Panama south along
the Colombian Pacific coast will provide strong low-level moisture
convergence today . Upper-level diffluence will lead to strong
deep convection over the same region. A tropical wave currently
extended over western Venezuela will interact with an upper-level
dynamic support linked to a region of diffluence. This tropical
wave will move through the region increasing lower-level moisture
convergence over sectors of Venezuela and Colombia. The
upper-level area of diffluence will not be well aligned to the
lower-level dynamics today and Thursday; keeping deep convective
rainfall limited and supporting rainfall maxima of 15-35 mm. By
Friday, the upper-level counterclockwise circulation, currently
centered over Colombia, will drift  its center from south of
Panama to the west providing the necessary upper-level dynamic to
enhance updrafts. Meanwhile, in the lower-levels the interaction
of the tropical wave with topography and the monsoon trough
forcing will lead to a significant increase in PWAT anomaly.
Rainfall accumulation maxima of 30-50 mm are forecast from
northern Colombia to eastern Nicaragua.



Tropical Waves Initialized at 12 UTC:
Typ SOF INIT 13/00 13/12 14/00 14/12 15/00 15/12 16/00 16/12
TW 14N  37W  40W  44W  47W  51W  55W  59W  64W  69W
TW 15N  60W  64W  68W  71W  75W  79W  83W  87W  90W
TW 20N  73W  75W  77W  79W  83W  87W  90W  93W  96W
TW 10N  88W  92W  96W  100W  104W  108W  112W  116W  Exits
TW 12N  103W  107W  110W  113W  117W  Exits




Sanchez-Perez...(WPC)

Tinoco-Morales...(WPC)


$$