[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 231801
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
101 PM EST Tue Jan 23 2018

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
1745 UTC.

...SPECIAL FEATURES...

Caribbean Gale Warning: The combination of high pressure in the
central Atlantic and lower pressures over northern Colombia
will continue to bring pulses of strong to minimal gale force
NE to E winds along and near the coast of Colombia during the
overnight hours through Thu night and possibly beyond into the
upcoming weekend. Seas are expected to be in the 9-14 ft range
with these winds. Please see latest NHC High Seas Forecast under
AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details.

Gulf of Mexico Gale Warning: Gale force winds are forecast to
begin early this afternoon in the far SW Gulf behind a cold front
that extends from the Florida Big Bend region to 25N86W and to
23N91W where it becomes stationary to 21N94W and cold front again
to just SE of Coatzacoalcos, Mexico. A gale warning has been
issued for the area S of 21N W of the front where minimal NW to N
gale force winds will occur. The latest model guidance indicates
that these gale wind conditions will persist longer than
previously advertised, and will now linger into early Thu
morning. During tonight, the cold front is forecast to reach from
the Straits of Florida to across the Yucatan Peninsula, with the
stationary portion transitioning back to a cold front across the
southern Bay of Campeche. The cold front will weaken slowly as it
moves across the SE Gulf Wed, and exiting the area by late on Wed.
Please see the latest NHC High Seas Forecast under AWIPS/WMO
headers MIAHSFAT2/FZNT02 KNHC for more details.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from Africa near 06N09W to
03N19W. The ITCZ continues WSW from 03N19W to cross the equator
near 29W. Scattered moderate convection is N of the ITCZ within
30 nm either side of a line from 02N31W to 03N39W. Similar
activity is within 60 nm S of the ITCZ between 36W-39W.

...DISCUSSION...

...GULF OF MEXICO...

A cold front extends from the Florida Big Bend region to 25N86W
and to 23N91W where it becomes stationary to 21N94W and
transitions back to a cold front again to just SE of
Coatzacoalcos, Mexico. A trough just NW of the cold front near
20N95W extends northwestward to just SE of Tampico. A pre-frontal
trough is analyzed from just SW of Tampa to 24N86W and to just N
of the NW side of the Yucatan Peninsula. The pre-frontal trough is
serving as a focus for active convection. As of 1745Z, scattered
moderate isolated strong convection is observed along and within
90 nm SE of the trough. In addition, an upper level disturbance
riding along a well entrenched southwesterly flow aloft is helping
to develop and maintain this convection. The latest available
lightning density data indicates that most of this activity
contains frequent lightning. Some of this activity may also be
attendant by gusty winds. Moisture guidance indicates that this
convective activity will move across the rest of the SE Gulf
through this evening. The cold front is forecast to move SE of the
area by late Wed. The high pressure behind it will strengthen as
is slides eastward across the southern portion of the SE United
States through Thu. The associated pressure gradient will support
fresh to strong northerly winds over much of the Gulf through Thu.

...CARIBBEAN SEA...

Broad upper level ridging is present across the western half of
the basin, while broad inverted troughing is noted elsewhere.
Upper level winds and satellite winds reveal a diffluent flow
pattern over the SW Caribbean. This appears to support scattered
moderate convection that is occurring from 10N to 13N W of 81W to
inland southern Nicaragua and far northern Costa Rica. This
activity is being sustained further by low-level speed convergence
present there. Patches of low-level moisture advecting westward
in the easterly flow are seen over the eastern Caribbean waters,
and also approaching the northern Windward Islands. Scattered
showers with gusty winds are possible with this moisture.

The Ascat pass from 1502Z this morning highlighted a large area
of fresh to strong NE to E winds over much of the central
Caribbean, with some winds to near gale force along the coast of
Colombia. Moderate to fresh trades are noted elsewhere across the
basin. The pressure gradient associated with high pressure N of
the area should support fresh to strong NE to E trades W of about
70W elsewhere outside the gale force winds area described above
through Thu. Strong NE winds are expected through the Windward
Passage after Wed. A cold front presently moving through the
eastern and S central Gulf of Mexico will move across the NW
Caribbean Wed night. The front is forecast to become stationary
and gradually wash out from central Cuba to Belize on Thu.
Strengthening high pressure in the wake of the front will bring
fresh to strong NE to E winds across the Caribbean, including the
Atlantic passages by late on Thu, with seas expected to build to
10 ft.

...ATLANTIC OCEAN...

High pressure ridging dominates the western Atlantic, with a
ridge extending westward into northern Florida. A robust mid/upper
level trough is evident on water vapor imagery extending from a
cyclonic circulation near 28N53W southwestward to 19N57W, and as a
shear axis to the eastern Caribbean near 15N65W. At the surface,
a trough is along 60W N of 24N. Isolated showers are within 60 nm
of the trough, and over some portions of the eastern Caribbean and
tropical waters s of 20N W of about 50W. Scattered showers and
isolated thunderstorms are seen N of 22N between 46W and 54W, with
a concentrated area of numerous showers within about 30 nm of
27.2N53W. A weak surface trough is located over the central
Atlantic along 40W N of 22N. Isolated showers are possible along
and within 60 nm either side of this trough. Expect shower and
isolated thunderstorm activity to expand eastward through Thu
ahead of the mid/upper level trough to near 43W. A cold front is
on track to move off the NE Florida coast this afternoon, and
reach from near 31N70W to Straits of Florida late on Wed, from
Bermuda to central Cuba late on Thu morning. Strong NE winds under
strengthening high pressure will follow behind the front.
Numerous showers and isolated thunderstorms with gusty winds will
precede the cold front.

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

$$
Aguirre
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