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Atlantic Tropical Weather Discussion



063 
AXNT20 KNHC 201734
TWDAT 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Tue Apr 20 2021

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 1200 UTC surface analysis and satellite imagery through 
1710 UTC.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coastal sections of Sierra 
Leone near 08N13W, 03N20W, to 01N25W. The ITCZ continues from 
01N25W, to the Equator along 35W, and continuing along the 
Equator at 45W, to 04N50W. Precipitation: widely scattered 
moderate to isolated strong in clusters is from 10N southward 
from 56W eastward.

GULF OF MEXICO...

A cold front passes through Lake Okeechobee in Florida, to 
25N85W in the Gulf of Mexico. The front becomes stationary at 
25N85W, and it continues to a 1012 mb low pressure center that 
is near 21N95W. The stationary front continues from the 1012 mb 
low pressure center, to 19N94W, and to 18N96W. A surface trough 
runs north-to-south, in the Yucatan Peninsula. Precipitation: 
scattered to numerous strong is within 180 nm to the south of 
the frontal boundary between 81W and 87W. Widely scattered 
moderate to isolated strong is from 25N southward from 87W 
eastward. Isolated moderate is elsewhere from 28N southward from 
88W eastward. It is possible that strong gusty winds and rough 
seas may be in some of the areas of the comparatively heavier 
and more intense precipitation.

A cold front extends from Fort Myers, Florida, to 24N90W, where 
it transitions to a stationary front to the Bay of Campeche. The 
cold front will be nudged southward, to the far southeastern 
Gulf of Mexico on Wednesday, and to the lower Straits of Florida 
on Wednesday night. High pressure in its wake, will shift 
eastward through Saturday night, as a cold front reaches eastern 
Texas. Fresh to strong southerly winds will develop in the NW 
and in the central Gulf of Mexico, from late Friday through 
Saturdat. Scattered rainshowers and thunderstorms will be 
focused along and near the cold front today and tonight. Some of 
this activity may produce strong gusty winds and rough seas. 

CARIBBEAN SEA...

Water vapor imagery and the GFS model for 250 mb show an 
anticyclonic circulation center that is in the SE coastal 
sections of Nicaragua. Upper level anticyclonic wind flow covers 
the Caribbean Sea from 70W westward. Upper level cyclonic wind 
flow covers the Caribbean Sea from 70W eastward, with an 
Atlantic Ocean trough. 

The GFS model for 700 mb shows: Broad cyclonic wind flow covers 
the SW corner of the Caribbean Sea, from 15N southward from 72W 
westward. Precipitation: scattered to numerous strong is in SE 
Nicaragua. Widely scattered moderate to isolated strong is in a 
line from central Panama toward SE Nicaragua.   

The monsoon trough is along 11N73W in northern Colombia, through 
the border of Colombia and Panama, beyond 07N80W and 07N86W, 
into the eastern Pacific Ocean. Precipitation: scattered to 
numerous strong is in SE Nicaragua. Widely scattered moderate to 
isolated strong is in a line from central Panama toward SE 
Nicaragua.   

Broken to overcast low level clouds, and isolated moderate 
rainshowers, cover the rest of the Caribbean Sea. The clouds and 
isolated moderate precipitation are moving with the 
surface-to-low level wind flow.

Fresh to strong trade winds in the central Caribbean Sea will 
diminish by late in the week, as high pressure in the central 
Atlantic Ocean shifts eastward, except near the coast
of Colombia where these winds will persist through the week.

ATLANTIC OCEAN...

A first cold front passes through 32N68W, to Lake Okeechobee in 
Florida. A second cold front passes through 32N73W to 30N80W, 
about 130 nm to 180 nm to the NW of the first cold front. 
Precipitation: widely scattered to scattered moderate, and 
isolated to widely scattered strong, are to the northwest of the 
line that passes through 32N50W, to 26N60W, and to 23N80W. It is 
possible that strong gusty winds and rough seas may be in some 
of the areas of the comparatively heavier and more intense 
precipitation.

A surface ridge extends from a 1023 mb high pressure center that 
is near 33N21W, to a second 1023 mb high pressure center that is 
near 28N33W, to a 1024 mb high pressure center that is near 
27N43W, 24N69W, across the Bahamas and Cuba, to 20N82W in the NW 
corner of the Caribbean Sea. Surface anticyclonic wind flow 
covers the Atlantic Ocean, away from the 32N68W-to-Lake 
Okeechobee in Florida cold front, eastward and southeastward.

The current weak cold front, that extends from 31N70W to West 
Palm Beach, Florida will stall E of 75W near 30N tonight, while 
W of 75W it will continue slowly southward. By early Wednesday, 
the stationary front will have move northward as a warm front, 
while the cold front will extend from NE of the Bahamas to the 
Florida Keys, and from near 31N69W to the central Bahamas and to 
west central Cuba by late Wednesday night, as another cold front 
moves into the NW waters. By late Thursday, both fronts will be 
weakening NE of the Bahamas, as high pressure builds into the 
area. The high pressure will shift eastward through Saturday 
night, as a stronger cold front approaches the southeastern 
U.S.A. coast. The stronger cold front will be preceded by fresh 
to strong southerly winds in the far NW waters, along with 
possible scattered showers and thunderstorms. 

$$
mt/ja