252
FXCA20 KWBC 211957
PMDCA

Tropical Discussion - International Desks
NWS Weather Prediction Center College Park MD
356 PM EDT Mon Jul 21 2025

Forecast Bulletin 21 July 2025 at 1530 UTC:

In the Lesser Antilles...

A potent tropical wave, that currently has an axis at 50.47W, will
begin to affect the region starting Wednesday and will bring with
it a significant increase in low-level moisture. In the low-to-mid
levels, speed divergence will be present across the region, which
will assist in the upward development of convection. Note, there
is a sharp gradient in the location of the speed divergence, with
the ECWMF extending it south of Dominica while the GFS has the
speed divergence affecting areas north of Montserrat. A subtle
change south (north) in the location of the speed divergence may
promote (inhibit) the development of convection. Another important
factor that may increase precipitation totals across the region is
the timing of the arrival of the tropical wave axis. The GFS model
has the tropical wave axis moving across the Lesser Antilles by
Wednesday afternoon while the ECWMF has the axis traversing the
region by Wednesday morning. A later arrival will allow for
diurnal effects to potentially enhance maximum precipitation
totals in the area. Overall, expect the greatest precipitation
impacts to occur between Wednesday afternoon through Thursday
afternoon. For now, we anticipate the total precipitation maxima
from Tuesday morning through Wednesday morning to be 20 - 35mm,
and 20 - 40mm from Wednesday morning through Thursday morning with
locally higher totals possible.

Another region of interest is Costa Rica and Panama. The Caribbean
Low Level Jet will continue to dominate in the Caribbean Basin for
the next three days. The days of greatest precipitation impact
will be Monday afternoon through Wednesday morning, when upper
level divergence, enhanced low level cyclonic flow (which is being
assisted by the CLLJ), and the Panamanian low will favor daily
total precipitation maxima of ~25 - 50mm. Thereafter, there
appears to be a decreasing trend in low level moisture from
Wednesday afternoon through Thursday morning, promoting a decrease
in total precipitation maxima in the region.


Note:
The low-level analysis charts are now expected to be issued
regularly.
The forecast bulletins are still being issued intermittently.

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

Tinoco-Morales...(WPC)



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