Tropical Weather Discussion
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AXNT20 KNHC 130558

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1258 AM EST Mon Nov 13 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.


The monsoon trough extends from the African coast near 09N13W to
09N18W. The Intertropical Convergence Zone axis extends from
09N18W to 06N36W to 07N43W to 04N51W. Scattered moderate isolated
strong convection is from 05N-14N between 19W-44W.



An upper level trough extends from the Great Lakes SSW to a base
over the SW Gulf basin, which is supporting a surface trough from
SE Louisiana adjacent waters near 28N89W to 23N91W. Isolated showers
are occurring within 150 nm E of the surface trough axis N of
26N. The tail of a shear line that is across S Florida extends into
the SE Gulf from 26N81W to 25N83W. South of this boundary,
southerly diffluent flow supports scattered showers and isolated
tstms across the Yucatan Channel, the E Yucatan Peninsula and the
Florida Straits. Otherwise, surface ridging prevails elsewhere. A
tight pressure gradient between the ridge and lower pressure over
the W Caribbean supports fresh to locally strong ENE winds E of
90W, including the aforementioned areas being affected by
convection. Moderate to fresh NNE winds are elsewhere. The shear
line is expected to slowly dissipate through Monday night as
stronger NE winds weaken.


Broad low pressure prevails across the western Caribbean
underneath a middle level low in the NW basin and southerly upper
level diffluent flow. This atmospheric scenario supports a surface
trough along 18N78W to 14N79W with associated numerous heavy
showers and tstms from 14N-19N between 77W-81W and scattered
moderate convection and tstms elsewhere W of 75W. Middle to upper
level diffluence support scattered showers across the western half
of Hispaniola and isolated showers across the remainder Dominican
Republic. A middle level ridge and dry air aloft provide stability
and generally fair weather to the eastern half of the Caribbean. A
tight 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 locally strong winds in the NW
Caribbean N of 14N W of 75W. 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 persist.


Middle to upper level diffluence support scattered showers across
the western half of Hispaniola and isolated showers across the
remainder Dominican Republic. This overall pattern will persist
through Tuesday.


Southwesterly to westerly flow aloft support cloudiness and
possible isolated showers across the Grand Bahama Bank and the
northern and central Bahamas. To the east, middle to upper level
diffluence support scattered showers N of the Windward Passage and
Hispaniola to 21N. To the N of this region, a shear line extends
from 28N66W to 26N74W to Florida near 26N80W. In the NE basin, a
1013 mb low is centered near 29N34W. Environmental conditions are
expected to be conducive for some additional development, and the
system could become a subtropical cyclone during the next few days
while it moves slowly northeastward. There is a low chance of
cyclogenesis within the next 48 hours. Lastly, a surface trough
extends from 25N25W to the Cape Verde Islands supporting showers
there and northward from 15N-30N between 21W-33W. Otherwise,
surface ridging prevails elsewhere.

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