Tropical Weather Discussion
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AXNT20 KNHC 121052

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
552 AM EST Sun Nov 12 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 0600 UTC surface analysis and satellite imagery through
1045 UTC.


The monsoon trough extends from the African coast near 13N16W to
12N20W. The Intertropical Convergence Zone axis extends from
12N20W to 10N35W to 08N45W to 08N49W. Scattered moderate
convection and tstms are from 03N-14N between 21W-46W. A surface
trough is west of the ITCZ extending from 11N48W to 06N51W
supporting isolated showers from 04N-13N between 46W-56W.



Strong high pressure anchored over Maine extends SSW across the
SE CONUS and then across the Gulf waters. A weakness in the ridge
is analyzed as a surface trough from the coast of Mississippi
near 30N88W to 25N91W, which is generating isolated showers
within 75 nm either side of its axis. A tight pressure gradient
between the strong ridge and lower pressure over the SW N Atlc and
the W Caribbean supports fresh to locally strong ENE winds E of
the surface trough, the Yucatan Channel and the Florida Straits.
Moderate NE to E winds are elsewhere. Otherwise, water vapor
imagery indicate broad upper troughing over the basin along with
relatively dry air aloft, which is maintaining generally fair
weather conditions. The surface trough will continue to move
across the NW Gulf through this afternoon and then dissipates.
Fresh to locally strong winds will prevail across the eastern half
of the basin through Tuesday.


Broad low pressure prevails across the western Caribbean. A
surface trough extends from 18N83W to Costa Rica coastal waters
near 10N83W. Water vapor imagery indicate the trough is supported
aloft by a mid-level low stretching from the Windward Passage to
the SW Caribbean. In addition, a favorable diffluent environment
remains over the western and central Caribbean, which is
supporting scattered showers and tstms within 75 nm E of the
trough axis and from 15N-21N W of 80W. A middle-level low NE of
the Mona Passage supports scattered showers and tstms that extends
to the Passage and across portions of Puerto Rico. A strong
pressure gradient between high pressure N of the area and the
broad area of low pressure in the western half of the Caribbean
supports fresh to strong winds in the NW Caribbean N of 18N W of
80W. The synoptic pattern aloft will continue in place through
Monday as the upper level troughing over the Gulf of Mexico and SW
North Atlc will be slow to weaken into early next week.
Otherwise, moderate to occasional fresh trades E of 75W will


Scattered showers and isolated tstms continue across the island
this morning as a favorable middle to upper level diffluent
environment prevails. Upper level troughing is expected to persist
to the NW over the SE Gulf of Mexico and SW North Atlc through
tonight with persistent convection expected across the island,
adjacent coastal waters and much of the north-central Caribbean
Sea. Potential hazards of localized flooding and life-threatening
mud slides are possible, especially if stronger convection
develops during peak daytime heating and instability today and


A stationary front extends across the SW North Atlc from 30N64W
SW to 27N73W then to the Florida coast near 27N80W. A middle-
level low NE of the Mona Passage supports scattered showers and
tstms S of 22N between 63W-73W. To the east, a surface trough
extends from 30N56W to 25N57W with widely scattered showers and
isolated tstms within 210 nm E of its axis. The surface trough
remains within the southern periphery of a surface ridge anchored
by a 1034 mb high centered NE of the Azores. Finally, a 1016 mb
low near 30N35W and associated surface trough interacting with an
upper-level low continues to produce an elongated area of
disorganized showers and thunderstorms N of the area.
Environmental conditions are expected to be conducive for a non-
tropical low to form during the next day or so. The system could
gradually acquire some subtropical characteristics by the middle
of next week while it moves slowly northeastward.

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