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FXCA20 KWBC 151841
PMDCA

Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
241 PM EDT Wed Apr 15 2026

Forecast Bulletin 15 April 2026 at 1842 UTC:

An upper level trough is currently located across the Greater
Antilles and is expected to begin to dig into the Caribbean Sea on
Wednesday. By Thursday, its base will extend into the Gulf of
Panama. As the trough deepens, its exit region will support the
enhancement in upper divergence in Colombia and Venezuela for
Wednesday and Thursday. Across the Caribbean, a preexisting low
level induced trough will continue to affect Hispaniola, Puerto
Rico, and the Virgin Islands (VI). This trough is slowly migrating
westward and its axis is expected to be near 66W by Wednesday
afternoon. Starting Wednesday afternoon, a southerly to
southeasterly low level wind will begin to dominate across Puerto
Rico and the VI, leading to an increase in moisture convergence.
Meanwhile in Hispaniola, north and northeasterly low level winds
will dominate ahead of the trough axis and will favor moisture
convergence along the northern coast of the island, particularly
during the day on Wednesday. As the trough axis moves overhead,
moisture convergence will decrease. Thus, the period with the
greatest precipitation impact on Wednesday will be during the day
and decreasing for the evening. Thereafter, easterly low level
winds will dominate across Hispaniola, Puerto Rico, and the VI.
The mid-to-upper level trough will still be over the region for
Thursday and Friday and it will support the above normal
precipitable water values for the eastern Greater Antilles. With
respect to total precipitation maxima, expect moderate maxima for
the next three days across the region.

With the approach of the mid-to-upper level trough, expect an
increase in upper wind speeds across Colombia and Venezuela, which
will favor upper divergence for Wednesday and Thursday. On
Wednesday, a northwesterly low level wind flow will be dominating
across the Andean region of Colombia. This pattern will enhance
orographic effects and moisture convergence. Thus, expect elevated
total precipitation maxima. Starting on Thursday and continuing
into Friday, northerly low level winds will aid in the transport
of dry air from the Caribbean into Colombia, assisting in the
decrease in total precipitation maxima in the region.

Across southern Colombia and Ecuador, surface to low level onshore
flow will continue for the next three days. Precipitable water
values will remain above 45mm for the next three days as well. On
Wednesday and Friday, expect light total precipitation maxima in
Ecuador and southern Colombia. On Thursday, there will be an
increase in low level westerly winds across the low and mid levels
during the day, which will support more intense moisture
convergence and in turn enhanced total precipitation maxima in
Ecuador and southern Colombia. By Friday, a ridge will develop
offshore of Ecuador, limiting moisture convergence.

In the Amazon Basin, low level troughs will be traversing the
Basin for the next three days that will enhance moisture
convergence and vertical ascent. Expect moderate total
precipitation maxima in the vicinity of these features. In the
northwest Amazon Basin, for Wednesday and Thursday, 850mb level
winds will be converging and will lead to increasing moisture
convergence.  Moderate total precipitation maxima is likely with
this pattern. On Thursday and Friday, another region of interest
will be the west-central Amazon Basin, where moisture convergence
will be present. In the mid and upper levels, there will be a
diffluent upper level pattern that will favor convective
ventilation. Thus, expect enhanced total precipitation maxima for
Thursday and elevated maxima for Friday. Meanwhile along the
Amazon Delta, the moisture plume associated with the Intertropical
Convergence Zone (ITCZ) will continue to converge for the next
three days. At the same time, a mid-level ridge will be
intensifying across the Guianas and will favor the increase in
easterly low level winds across northern Brasil.

In Central America and southern Mexico, an upper level ridge will
strengthen in the region, which will increase subsidence in the
region. Meanwhile in the Caribbean Sea, the upper trough will help
sustain the Papagayo Low Level Jet (LLJ), which will promote the
development of a surface-to-low level high pressure system to its
north and a low pressure system to the south. To the north of the
LLJ, expect enhanced confluence as the high pressure system will
interact with a low pressure system to its north. This pattern
will support on-shore flow into the southern coast of Chiapas,
coastal Guatemala, and coastal El Salvador. In Costa Rica, there
will be enhanced on-shore flow as well, which will also support an
increase in moisture convergence. In these two broad regions,
expect light total precipitation maxima for the next three days.


Tinoco-Morales...(WPC)


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