[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 161730
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
130 PM EDT Mon Oct 16 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 1200 UTC surface analysis and satellite imagery through
1500 UTC.

...SPECIAL FEATURES...

A sharp negatively tilted upper trough reaches from off Cape
Hatteras to the central Bahamas. This has been supporting a
surface trough reaching from 31N70W to 1011 mb low pressure near
24N71W, to the north of the Turks and Caicos Islands. Divergence
aloft on the east side of the upper low is enhancing a large area
of showers and thunderstorms sheared to the east of the surface
low, mainly from 21N to 31N between 65W and 72W. Strong southeast
winds in the areas of strong convection have been noted in various
scatterometer and buoy data over the past couple of days as this
complex has moved from off the Leeward Islands to its present
position. Some development of this low will be possible during the
next day or so while it moves generally northward over the
western Atlantic. However, upper- level winds are expected to
become unfavorable for tropical cyclone formation by late Tuesday,
and the system is likely to merge with a front and become
extratropical on Wednesday. There is a medium chance of tropical
cyclone formation within 48 hours.

As of 1500 UTC a cold front extends from near Apalachicola Florida
to 25N93W to near Poza Rica on the coast of Mexico south of
Tampico. A tight pressure gradient and cool dry air associated
with the front will allow northerly winds to continue to funnel
along the coast of Mexico reaching minimal gale force from Tampico
to Veracruz Monday through late today, with seas reaching 8 to 16
ft. The front will reach from Florida Big Bend to 23N93W to the
Bay of Campeche late today, then gradually lose identity across
the southeast Gulf of Mexico through mid week.

...TROPICAL WAVES...

A tropical wave extending from 15N47W to 08N49W, moving W at 20
kt. There remains good continuity of this wave on various
satellite imagery with clusters of scattered moderate convection
are from 07N-12N between 45W-52W.

A tropical wave a little farther west and south, reaching from
13N55W to 06N58W and approaching Barbados. This wave is not as
well defined, with drier air is impinging on the northern extent
of this wave, although there is better evidence of the wave axis
farther south near the Guyana coast.

A more substantive tropical wave is analyzed over the central
Caribbean, from the Windward Passage to the central coast of
Colombia. There is good continuity in various satellite data and
satellite derived winds showing a broad wave axis traversing the
central Caribbean. No significant convection is noted currently
in the area of the tropical wave axis, largely due to dry
subsident air aloft moving into the northwest and north central
Caribbean at the base of an upper trough north of the area.

...ITCZ/MONSOON TROUGH...

The monsoon trough extends from the Senegal coast near 15N17W to
08N27W, where it transitions to the intertropical convergence
zone and continues to 06N35W then on to near Trinidad. Scattered
moderate convection is from 09N to 13N between 45W and 53W
associated with the tropical wave near 49W.

...DISCUSSION...

GULF OF MEXICO...

As of 1500 UTC, a cold front is over the N Gulf of Mexico
extending from the Florida Panhandle to south of Tampico Mexico.
See above. Winds are already reaching gale force along the coast.
Scattered showers and a few thunderstorms are active along the
frontal boundary, especially where the coastal barrier jet pushes
along the coast of Mexico. Seas are building to 10 ft over the
northwest Gulf in the area of strong winds west of the front.
Gentle breezes and slight seas are noted elsewhere. High pressure
building north of the area in the wake of the front will allow fresh
to strong winds across the basin late in the week.

CARIBBEAN SEA...

Strong southeast winds are noted over the northeast Caribbean in a
recent buoy and scatterometer data, between high pressure over the
central Atlantic and an approaching tropical wave east of
Barbados. Showers and thunderstorms are active from Martinique to
Puerto Rico. Deep dry air is noted elsewhere, related in part to
dry subsident air aloft filtering over the Caribbean on the south
side of an upper trough northeast of the Bahamas. Moderate winds
and seas are observed currently, but this will not last. High
pressure building north of the area will allow strong winds to
pulse over the south central Caribbean, mainly at night and in the
wake of passing short waves through mid week. This trend will
persist late in the week, with strong winds and building seas
forecast for across the eastern Caribbean.

...HISPANIOLA...

A negatively tilted upper trough reaching from off the Carolinas
through the southern Bahamas into central Hispaniola. Dry air on
the west side of this trough is preventing much cloud cover over
Haiti and the western Dominican Republic. However, divergence
aloft interacting with local sea breezes is enhancing showers over
the more moist eastern portions of the Dominican Republic. A
surface trough lingering across the southern Bahamas into
Hispaniola through mid week will be the focus for a few showers
mainly over the Dominican Republic as the upper trough slowly
drifts east and dampens out. A tropical wave moving across
Hispaniola mid week and Thu will bring additional potential for
showers, ending by late week as drier deep layer moisture moves
into the region.

ATLANTIC OCEAN...

A 1011 mb low is centered N of Hispaniola near 23.5N71W. A
surface trough extends N from the low to 29N71W. Scattered
moderate to strong convection is from 20N-25N between 65W-70W.
See above. A 1031 mb high is centered over the central Atlantic
near 35N43W, enhancing fresh trade winds in the deep tropics.
Elsewhere, the tail end of a cold front is producing scattered
showers over the Canary Islands and areas of Saharan dust continue
to move off northeastern Africa into adjacent Atlantic waters as
far west as 40W.

For additional information please visit
http://www.hurricanes.gov/marine

$$
Christensen
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