[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 050552
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
152 AM EDT Wed Sep 5 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 0000 UTC surface analysis and satellite imagery through
0545 UTC.

...SPECIAL FEATURES...

Hurricane Florence is centered near 20.7N 43.9W at 05/0300 UTC,
which is about 1095 nm E of the northern Leeward Islands or 1315
nm ESE of Bermuda moving WNW at 10 knots. The estimated minimum
central pressure is 976 mb. The maximum sustained winds have
increased to 85 kt with gusts to 105 kt. Satellite imagery shows
the overall cloud pattern of Florence is very symmetrical and
rather compact in size. A small eye, 15 nm in diameter, is
evident in the imagery. The imagery shows scattered to numerous
strong convection within 60 nm of the center, except for 90 nm in
the SW quadrant. Scattered moderate within 30 nm of a line from
23N42W to 22N44W denote an outer rainband. Latest NHC forecast
has Florence continuing on a WNW motion through Wed night before
it takes a northward turn on Thu. Florence is forecast to
strengthen slightly through Wed morning, then begin to weaken
afterwards through Fri. Public Advisories on Florence are issued
under WMO/AWIPS headers WTNT31 KNHC/MIATCPAT1. Forecast Advisories
are issued under WMO/AWIPS headers WTNT21 KNHC/MIATCMAT1.

Tropical Storm Gordon is crossing the coast near 30.3N 88.4W at
05/0300 UTC, which is about 25 nm ESE of Biloxi, Mississippi or 30
nm SSW of Mobile, Alabama. Gordon is moving NW or 315 degrees at
13 kt. Estimated minimum central pressure is 997 mb. The maximum
sustained winds are 60 kt with gusts to 75 kt. Latest satellite
imagery and NWS radar imagery show scattered moderate isolated
strong convection within 60 nm of the center in the N semicircle
and 30 nm of the center in the S semicircle. Scattered moderate
convection is to the southeast of Gordon over the north- central
gulf waters within 30 nm of a line from 28N88W to 29N86W. Deep
convection noted a few hours ago over much of the Florida
panhandle and over sections of northern Florida haver decreased
significantly, except for over the far western Florida panhandle.
Now that Gordon is moving inland, the latest NHC forecast calls
for it to weaken rapidly to a depression by this evening near the
northeastern Louisiana/Mississippi border. Public Advisories on
Gordon are issued under the WMO/AWIPS headers WTNT32
KNHC/MIATCPAT2. Forecast advisories on Gordon are issued under
WMO/AWIPS headers WTNT22 KNHC/MIATCMAT2.

A strong tropical wave has its axis extending from near 04N26W to
13N26W and to near 19N24W, with a 1008 mb low along the wave axis
near 11N25W. This system depicts a broad area of low pressure
with disorganized cloudiness. Deep convection, for the time being,
is rather limited. It is observed as that of scattered strong
type intensity within 30 nm of a line from 17N22W to 15N25W to
13N27W. Scattered moderate convection is within 30 nm of 12.5N29W.
This system has a medium chance of becoming a tropical cyclone
during the next 48 hours. Refer to the latest NHC Tropical Weather
Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more
information.

...TROPICAL WAVES...

A Caribbean Sea tropical wave has its axis along 77W/78W south of
21N. The wave is moving under a NE to SW oriented cyclonic shear
axis that stretches from an elongated cyclonic circulation well
north of the Caribbean southwestward to central Hispaniola, to
near 15N76W and to central Panama. Scattered moderate isolated
strong convection is moving quickly westward ahead of the wave
just south of central Cuba from 19N to 21N between the wave and
82W. Isolated moderate convection is seen from 15N to 18N between
the wave and 81W. Scattered showers and isolated thunderstorms are
over and near the Windward Passage.

The northern portion of an eastern Pacific tropical wave reaches
along 96W northward to the far southwest Gulf of Mexico to near
21N. It is moving westward at 15 kt. Scattered moderate
convection is within 60 nm north of the wave from 21N to 23.5N
between 96W and 97W.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis through the coastal sections of Senegal
near 15N17W to the 1007 mb low associated with the broad area
of low pressure described above under Special Features, and
continues to 09N31W to 10N43W. The ITCZ axis extends from 10N43W
to 08N50W to 09N59W. Scattered moderate isolated strong convection
is within 240 nm S of the trough between the coast of Africa and
18W. This activity spreads inland the coast for about 180 nm.

...DISCUSSION...

GULF OF MEXICO...

Please see the SPECIAL FEATURES section above for details on
Tropical Storm Gordon.

An upper-level inverted trough is to the west of Gordon, from
southeastern Louisiana to an upper-level cyclonic circulation
just northwest of the Yucatan Peninsula near 22N91W and to the
eastern Bay of Campeche. An upper-level ridge extends from
southwestern Louisiana to inland northeastern Mexico.
Aside from convection associated with Tropical Storm Gordon,
the availability of ample moisture along with the presence of
the upper trough and low is allowing for the atmosphere to be
unstable over much of the western and central gulf waters. As a
result, scattered showers and isolated thunderstorms are seen west
of 90W, with the most of the activity mainly occurring to the
west of 94W. Isolated showers and thunderstorms are elsewhere over
the remainder of the gulf. The shower and thunderstorm activity
should remain quite active through this evening.

CARIBBEAN SEA...

An upper-level cyclonic shear axis is noted on water vapor
imagery extending in NE to SW fashion from an elongated cyclonic
circulation well north of the Caribbean southwestward to central
Hispaniola, to near 15N76W and to central Panama. This feature is
interacting with the tropical wave along 77W/78W initiating deep
convection just south of central Cuba as described above under the
Tropical Waves section. Otherwise, isolated showers and
thunderstorms are over the remainder of the Caribbean west of 79W,
while isolated showers are east of 79W.

The easternmost sector of the eastern Pacific monsoon stretches
along 09N/10N to across northern Panama, to the far SW Caribbean,
and to northwestern Colombia. Widely scattered showers and
isolated thunderstorms are seen from 09N-10N east of 81W to inland
northwestern Colombia.

The tropical wave along 77W/78W will move across the rest of the
central Caribbean through this morning, then across the western
Caribbean later on Wed and through Fri. The gradient associated
with a relatively weak surface ridge, that is to the north of the
region, will maintain moderate to fresh trade winds mostly
everywhere, through the next several days.

ATLANTIC OCEAN...

Please see the SPECIAL FEATURES section above for details on
Hurricane Florence and on a new area of broad low pressure
over the far eastern Atlantic with a medium chance of tropical
cyclone formation.

An elongated upper-level cyclonic circulation is near 26N66W, with
a trough extending southwestward to Hispaniola. Upper-level
cyclonic wind flow covers the area north of 19N between 57W and
77W. At the surface, a trough is analyzed from near 21N63W to
31N60W. Scattered showers and thunderstorms are noted north of
22N between 61W and 70W. Isolated showers and weak isolated
thunderstorms are elsewhere west of 59W.

Strong high pressure to the north and northeast of Hurricane
Florence is suppressing the atmosphere environment, maintaining
it pretty stable over the eastern Atlantic, except near the broad
area of low pressure as described above.

A weak pressure pattern will maintain gentle to moderate easterly
winds across the area through the next few days. Easterly swell
from Hurricane Florence will move into the open waters east of the
Bahamas beginning late this afternoon through Sat.

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

$$
Aguirre
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