Tropical Weather Discussion
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AXNT20 KNHC 200605

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
205 AM EDT Sat May 20 2017

Tropical Weather Discussion for North America, Central America
Gulf of Mexico, Caribbean Sea, northern sections of South
America, and Atlantic Ocean to the African coast from the
Equator to 32N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 0000 UTC surface analysis and satellite imagery through
0545 UTC.


Please refer to the METEO-FRANCE High Seas Forecast, listed on
GRANDLARGE/METAREA2. Frequent wind gusts to gale-force are
forecast for the area of AGADIR. These conditions will dissipate
during the next 6 hours.


A tropical wave is in the eastern Atlantic with axis extending
from 12N24W to 03N24W, moving west at 10-15 kt. The wave is mainly
in an unfavorable wind shear environment. Satellite imagery also
show Saharan dry air and dust in the wave environment, which is
supporting the lack of convection at the time.

A tropical wave is in the west Atlantic with axis extending from
13N56W to 06N56W, moving west at 20 kt within the last 24 hours.
CIRA LPW and SSMI TPW imagery show the wave is in a dry region. In
addition, unfavorable wind shear, Saharan dry air and dust are in
the wave environment supporting lack of convection at the time.

A tropical wave is in the far western Caribbean with axis
extending from 19N84W to 08N82W, moving west at 5-10 kt within the
last 24 hours. The wave continues embedded in a very moist
environment and is under a diffluent environment aloft that
support scattered heavy showers and tstms in the SW Caribbean S of
14N west of 80W.


The Monsoon Trough enters the tropical Atlantic through Guinea
near 14N17W and continues to 08N23W. The ITCZ extends west of a
tropical wave from 05N27W to 02N35W to the coast of Brazil near
02S42W. Outside of the convection associated with the tropical
wave, no significant convective activity is noted at this time.



Return flow prevails across the basin, which is advecting moisture
from the Caribbean into the NW Gulf to support dense fog N of 22N
west of 90W according to both GOES IFR probabilities and surface
data. In the SW Gulf, middle level diffluence support scattered
showers in the central and western Bay of Campeche. Scattered
heavy showers and tstms are within 60 nm off the Florida Big Bend
coast supported by upper level diffluence. Water vapor and CIRA
LPW show dry air across the remainder basin, which favors clear
skies and fair weather. Otherwise, moderate southeasterly flow
dominates basin-wide, except for locally fresh winds off the Texas
coast and northeasterlies off the western Yucatan Peninsula. No
major changes are expected until Sunday night when a weak cold
front is forecast to move off the Texas coast.


The main feature in the Caribbean is a tropical wave extending
from the NW basin near 19N84W to inland Nicaragua, Costa Rica and
northern Panama. Abundant moisture in the SW basin as well as
upper level diffluence support heavy showers and tstms in this
region. See the tropical waves section for further details.
Shallow moisture across the northern basin support cloudiness with
possible isolated showers, but mainly dust has been reported in
the Dominican Republic as well as the Lesser Antilles. Dry air
subsidence from aloft and strong deep layer wind shear support
clear skies elsewhere. High pressure over the Atlantic tightens
the gradient in the Caribbean to support strong to near gale
force winds over the south-central Caribbean, including the Gulf
of Venezuela. Fresh to strong winds are across the remainder of
the central Caribbean, with fresh southeasterly winds just north
of Jamaica. Fresh to strong trades will persist over the central
Caribbean during the upcoming weekend.


Upper-level flow has become more zonal across the island with a
break in the heavy rainfall from the past few days. Moisture
is forecast to diminish over the upcoming weekend as the upper-
level trough continues to drift eastward and the wind flow turns
more to the NW. Fair weather is forecast during the day this
weekend, however model guidance suggest a high chance of showers
at night, both Saturday and Sunday.


A Gale Warning is in effect for the far east Atlantic waters.
Please refer to the SPECIAL FEATURES section above for details.
Surface high pressure dominates the Atlantic Ocean being anchored
N of the area. The exception is a surface trough that extends
from 25N58W to 21N59W with scattered to isolated showers east of
the trough to 50W. Abundant mid-upper level moisture persists
ahead of this upper trough forecast to drift eastward.

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