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Atlantic Tropical Weather Discussion

AXNT20 KNHC 201801

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
101 PM EST Tue Nov 20 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. 


The monsoon trough axis extends from the coast of Liberia near 
05N09W to 0512W, where latest scatterometer data indicates the 
ITCZ axis begins and continues to 05N21W to 03N30W to 05N37W and 
to 04N45W. Scattered moderate convection is along and within 60 nm
north of the ITCZ axis. Scattered showers are within 90 nm either
side of the ITCZ axis between 12W and 17W.


In the upper-levels, broad troughing that extends from the Great
Lakes region of the U.S. to the far NW Gulf is keeping west to 
southwest upper winds over the northern portion of the Gulf. At 
the surface, a cold front is making headway the Florida panhandle,
and as of 15Z, it is analyzed from near Tallahassee, Florida
southwestward to 28N90W where it becomes stationary to 28N92W and 
warm front to a 1019 mb low at 28N92W. A cold front extends from
the low to 24N95W and to inland Mexico at 21N97W. It continues 
northwestward well inland Mexico. Satellite imagery shows 
multilayer clouds with embedded scattered showers and isolated 
thunderstorms within 150 nm southeast and south of the cold front 
to the east of 90W, and also within 60 nm either side of the 
cold front from 21N to 25N. Broken to overcast low clouds with 
embedded areas of rain and scattered showers are west and 
northwest of the cold front west of 90W, except within about 30 nm
of the Texas coast north of Corpus Christi. A stationary front 
extends northeast to southwest from the Atlantic to across central
Florida to near 28N83W, where it transitions to a trough to 
24N86W. Scattered showers and isolated thunderstorms are within 60
nm east of the trough north of 25N, and within 90 nm west and 
northwest of the trough from 24N to 25N.

As for the forecast, the 1019 mb low will dissipate by this
evening, while the cold front will become stationary from southern
Florida to the NW Gulf near 26N95W and to near Veracruz Mexico by
Thu Night. The trough over the eastern Gulf will dissipate by late


Water vapor imagery shows broad upper-level anticyclonic flow
covering just about the entire basin west of about 67W, with the 
associated upper anticyclone centered over the far eastern Pacific
Ocean. Broad cyclonic upper-level flow is east of 67W. A mid- 
level inverted trough extends from Panama to 15N82W and to near 
18N83W. Scattered patches of low-level clouds moving quickly 
westward with isolated showers are seen south of 20N west of 80W, 
while scattered moderate isolated strong convection is confined to
the south of 13N west of 79W. This activity is more due to low- 
level speed convergence from strong trades advecting into an area
of lighter winds. Isolated showers also moving quickly westward 
are elsewhere across the basin. An area of scattered showers and 
thunderstorms is over the eastern Caribbean from 12N to 15N 
between 66W and 70W. This activity is being enhanced by a mid- 
level shortwave through. 

As for the forecast, fresh to strong trades will continue along 
the coast of Colombia through Thu. Large long period NE swell 
over the Atlantic will continue to impact the waters east of the 
Lesser Antilles through Wed afternoon. 


A western Atlantic cold front enters the area near 32N74W and
continues to 29N77W, where becomes stationary to inland central 
Florida near Coco Beach and continues to the west-central Florida 
coast. Scattered showers and isolated thunderstorms are noted 
north of 27N and west of 76W. This activity is being aided by 
a mid to upper shortwave trough that is rounding the base of 
a broad upper trough northwest of the area. A weak 1017 mb low is
centered at 30N71W, with a trough extending southwestward to
the central Bahamas and to the coast of Cuba at 22N78W. Scattered 
showers and thunderstorms are ahead of the trough north of 28N
between 60W and 69W. 

Over the far eastern Atlantic, a narrow upper-level trough extends 
from near 32N08W to 22N12W and to an upper low at 11N18W. This
feature is sustaining a cold front that extends from a 1012 mb low
just north of the area at 33N15W, southwestward from this low to
30N20W to a frontal wave at 29N30W and continues to 26N37W, where
it becomes a stationary front to 29N44W and to a 1019 mb low 
north of the area at 32N53W. A trough extends from this low to 
near 28N58W. A 1023 mb high is analyzed south of the stationary 
front near 27N49W. Satellite imagery shows broken to overcast 
mainly low and mid-level clouds along and within 60 nm south of 
the cold front and frontal wave east of 30W. Patches of rain 
and scattered showers are possible with these clouds. Isolated
showers are possible elsewhere along the stationary front and 
with the trough that extends from the 1019 mb low. Relatively weak
high pressure is present over the remainder of the discussion

As for the forecast, the trough that extends to the central
Bahamas and to near the coast of Cuba will dissipate by Wed. The 
cold front over the northwest portion will move southward over 
the waters north and northeast of the Bahamas Thu through Fri 
night, then become stationary Sat. A tight pressure gradient 
resulting from strong high pressure that will build southward Fri 
through Sat night will bring strong winds northeast of the 
Bahamas. Seas outside the Bahamas will build to between 9 and 14 
ft from Fri through Sat night.

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