Tropical Weather Discussion
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AXNT20 KNHC 182254

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
654 PM EDT Sat Mar 18 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 1800 UTC surface analysis and satellite imagery through
2215 UTC.

The Monsoon Trough extends from the African coast near 06N10W to
the Equator near 24W. Widely scattered moderate convection is S
of 06N between 12W-35W.


Water vapor imagery indicates mostly dry air and stable conditions
over much of the basin as an upper level trough axis extends from
over the Florida Big Bend region W-SW to 27N95W over the NW Gulf
waters. The stable conditions aloft continue to support surface
ridging anchored by a 1028 mb high centered near 27N87W and a 1026
mb high centered along the Mexico coast near 21N97W. Gentle to
moderate anticyclonic wind flow prevails across the basin this
evening as the high will gradually drift westward through early
Sunday. As the high shifts...a cold front is expected to emerge
off the Gulf coast E of 90W tonight and sweep southward across
the Florida peninsula and far eastern waters through Sunday
afternoon. Ridging west of the front will remain the primary
influence for the Gulf Monday and Tuesday.

Mostly west-southwesterly upper level flow is noted on water
vapor imagery over much of the Caribbean basin this evening. This
southwesterly flow over western portions feed NE into broad upper
level troughing over the central North Atlc in support of a
stationary front analyzed from the Windward Passage to eastern
Honduras near 15N83W. Widely scattered showers and isolated tstms
are occurring within 150 nm either side of the front. Some of the
low-level moisture and isolated shower activity continues to feed
across interior portions of Nicaragua...Honduras...and Guatemala.
Otherwise...a few isolated showers are possible across the eastern
Caribbean from 12N-17N between 62W-69W. Moderate to fresh trades
are expected through the overnight hours into Sunday...generally
E of the front...while moderate to fresh NE winds will prevail
across the NW Caribbean through the overnight W of the front. The
overall pressure gradient generating these winds is expected to
relax by Sunday afternoon.

West-southwesterly flow aloft over the island in addition to a
stationary front analyzed across the Windward Passage and adjacent
western coastal waters is providing for isolated showers this
evening. The front is expected to become diffuse by Sunday...
however isolated afternoon showers remain possible due to the
weakened remnant boundary.

A stationary front extends into the discussion area near 32N49W
SW to 26N60W to the Turks and Caicos islands then to the Windward
Passage and into the west-central Caribbean Sea. Scattered
showers and isolated tstms are occurring within 150 nm either side
of the boundary. A 1027 mb high centered near Bermuda continues to
provide mostly fair conditions to the remainder of the SW North
Atlc...however by late tonight into early Sunday the next cold
front is expected to emerge off the SE CONUS coastline with fresh
to strong SW winds ahead of the front and fresh to strong NW winds
after frontal passage. This frontal system is expected to reach
the central Atlc waters by Tuesday as high pressure builds back
in across the SW North Atlc waters. Farther east...the remainder
of the central Atlc is under the influence of a surface ridge
anchored by a 1029 mb high centered across the Azores near
39N27W. Finally...a weakening and broad 1012 mb low is centered in
the vicinity of the Canary Islands near 29N18W. Isolated showers
are possible across the Canary Islands...however is expected to
dissipate by Sunday evening as it drifts southward.

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