Atlantic Tropical Weather Discussion (Text)

AXNT20 KNHC 250000

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
700 PM EST Tue Jan 24 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 
2315 UTC.

A strong area of low pressure analyzed at 986 mb just S of Long 
Island near 40N72W has an associated cold front extending into 
the discussion area near 32N64W. The front continues SSW to 
26N69W to the N coast of Haiti then SW to the coast of Costa Rica. 
Gale force SSW winds are occurring N of 23N within 120 NM east of
the cold front over the SW North Atlc. Gale force winds are 
forecast to remain associated with the front into Thu. In 
addition...a surface trough is analyzed W of the cold front from 
32N69W to 25N70W. Near gale force WNW winds are occurring 
generally N of 29N with this feature and are expected to continue 
into Wed. See latest NWS High Seas Forecast under AWIPS/WMO 
headers MIAHSFAT2/FZNT02 KNHC for more details.

The Monsoon Trough extends from the African coast near 08N13W to 
05N18W. The Intertropical Convergence Zone axis extends from 
05N18W to 01N30W to the Equator near 42W and continues to the
coast of South America near 01S46W. Widely scattered moderate 
convection is S of 05N between 40W-46W.


Mid- to upper level ridge dominates the entire Gulf with axis 
along 88/89W. Strong subsidence was noted over the southern half 
of the Gulf with some upper level moisture streaming along the 
Gulf coast. The ridge supports clear skies over the entire Gulf 
and light anticyclonic surface flow E of 94W. A 1017 MB surface 
high was located over northeastern Yucatan. Moderate to fresh SSE 
winds are occurring W of 94W to the Texas coast. These southerly 
winds will gradually spread eastward through Wednesday as the next
cold front is expected to emerge off the Texas and Louisiana 
coasts by the afternoon. Winds behind the front will shift 
northerly as high pressure builds in across the lower Mississippi 
River valley Thursday into Friday.

Large anticyclone was centered over the East Pacific near the
equator along 85W with associated anticyclonic NW flow prevailing
over the Caribbean W of 70W with more westerly flow E of 70W.
Water vapor imagery indicated very dry and stable air in place 
over the entire basin. However...a middle to upper level trough 
is noted N of the basin over the SW North Atlc that supports a 
cold front analyzed from Haiti SW to the coast of Costa Rica
near 10N83W. With upper level dynamics fairly stable...the front 
continues to carry broken to occasional overcast skies and 
possible shallow low-level isolated showers within 90-120 NM 
either side of the front. Farther east...weak low-level 
convergence is generating cloudiness and possible isolated showers
across the eastern Caribbean...however no significant deep 
convection is expected. Otherwise...the front has disrupted the 
usual trade wind flow with generally light to moderate southerly 
winds E of the front...and light to moderate northerly winds 
expected W of the front through Wednesday as the front progresses 
to the east.

The proximity of the front over Haiti has resulted in broken to 
overcast low clouds with possible isolated showers over the
island. The cold front is expected to continue eastward over the 
island tonight and early Wed before high pressure builds in across
the region with drier conditions expected. The 12Z rawindsonde 
from Santo Domingo showed some increase in moisture below 750 MB 
with deep layered westerly flow. 

A negatively-tilted middle to upper level trough is noted on 
water vapor imagery over the SW North Atlc with axis extending 
from a mid-level vorticity maximum near 40N72W through 32N65W to 
a base near 25N62W. The troughing supports a cold front extending 
from 32N64W to 25N65W to the north coast of Haiti near 20N72W and
into the SW Caribbean Sea. As mentioned in the Special Features 
section...near gale to gale force wind are occurring on both side
of the front at this time. Scattered showers and isolated tstms 
are occurring N of 25N within 150-180 NM E of the front...while 
isolated showers are occurring within 120 nm E of the front S of 
25N. Mostly fresh to strong W to NW winds are occurring across 
the remainder of the SW North Atlc to the W of the front. High 
pressure is expected to build in across the region through 
Wednesday night gradually ushering in light to moderate 
anticyclonic winds. Farther east...the remainder of the central 
and eastern Atlc is under the influence of a pair of surface 
ridges. One surface ridge is anchored by a 1022 mb high centered 
near 28N48W and the other is a 1027 mb high centered near 32N18W 
extending a ridge axis SW to 20N40W. A weak surface trough along 
32N34W to 26N43W separated the areas of high pressure. 

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Page last modified: Wednesday, 25-Jan-2017 00:00:26 UTC