[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 101206
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 AM EDT Mon Sep 10 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 0600| UTC surface analysis and satellite imagery through
1145 UTC.

...SPECIAL FEATURES...

Hurricane Florence is centered near 24.9N 58.9W at 10/0900 UTC or
545 nm SE of Bermuda and about 465 nm NNE of the northern Leeward
Island moving WNW or 285 degrees at 8 kt The estimated minimum
central pressure is 969 mb. The maximum sustained wind speeds have
increased to 90 kt with gusts to 110 kt. Florence is rapidly
strengthening. Latest satellite imagery shows an apparent 10 nm
wide eye feature with Florence. Scattered moderate convection is
within 90 nm of the eye in the NE quadrant, within 60 nm of the
eye in the NW quadrant and within 30 nm in the semicircle.
Scattered moderate isolated strong convection is elsewhere within
180 nm of the eye in the NE quadrant and within 150 nm of the eye
in the SW quadrant. Scattered moderate convection is within 120
nm of the eye in the N and NW quadrants and within 60 nm of the
eye in the S quadrants. Scattered moderate convection is seen well
away from Florence from 21N to 24N between 56W and 63W, and from
24N to 27N between 61W and 64W. latest NHC advisory has Florence
continuing to strengthen as it tracks in west-northwester motion
during the next couple of days, before an expected turn to the
northwest occurs Wed night or on Thu. Public Advisories for
Florence are issued under WMO header WTNT31 KNHC and under AWIPS
header MIATCPAT1. Forecast/Advisories for Florence are issued
under WMO header WTNT21 KNHC and under AWIPS header MIATCMAT1.

Hurricane Isaac is centered near 14.7N 42.7W at 10/0900 UTC, which
is about 1070 nm E of the Windward Islands, moving or 275 degrees
at 12 kt.  The estimated minimum central pressure is 993 mb. The
maximum sustained wind speeds are 65 kt with gusts to 80 kt. Issac
has changed little during the past several hours. Isaac remains a
small hurricane, with scattered moderate to numerous strong convection
within about 75 nm of the center, except 60 nm in the N and S
quadrants. Scattered moderate convection denotes an outer
rainband within 30 nm of a line from 12.5N44W to 14N45W. Scattered
moderate convection is within 30 nm of 13N46W and within 30 nm of
14N47W. Latest NHC advisory forecasts a westward motion, with a
slight increase in forward speed the end of the week. Public
Advisories for Isaac are issued under WMO header WTNT34 KNHC and
under AWIPS header MIATCPAT4. Forecast/Advisories for Isaac are
issued under WMO header WTNT24 KNHC and under AWIPS header
MIATCMAT4.

Hurricane Helene is centered near 14.3N 28.9W at 10/0900 UTC,
which is about 265 nm W of the southernmost Cabo Verde Islands,
It is moving WNW or 285 degrees at 15 kt. The estimated minimum
central pressure is 984 mb. The maximum sustained wind speeds are
75 knots with gusts to 90 kt. Latest satellite imagery shows
scattered moderate to numerous strong convection within 120 nm of
the center in the NE, SE and S quadrants, and within 90 mm
elsewhere of the center. Latest NHC advisory forecasts Helene to
continue its present motion through the next couple of days,
before a turn to the NW occurs on Wed. Scattered moderate
convection is seen from 15N to 17N between 27W and 31W, and from
11N to 12.5N between 29W and 32W. Public Advisories for Helene are
issued under WMO header WTNT33 KNHC and under AWIPS header
MIATCPAT3. Forecast/Advisories for Helene are issued under WMO
header WTNT23 KNHC and under AWIPS header MIATCMAT3.

...TROPICAL WAVES...

The northern portion of a tropical wave with is axis along 92W
reaches northward to the eastern Bay of Campeche at 21N. Isolated
weakening convection is seen over far eastern Mexico from 17N to
19N between 91W and 93W. Isolated showers and thunderstorms are
over the Pacific waters near Guatemala and the Isthmus of the
Gulf of Tehuantepec of southern Mexico between 92W and 95W.

...MONSOON TROUGH/ITCZ...

The monsoon trough is analyzed over inland Africa. The ITCZ
extends from 07.5N47W to 07N58W. Isolated moderate convection is
within 60 nm S of the ITCZ betwewn 47W and 53W and within 60 nm
N of the ITCZ between 54W and 58W.

...DISCUSSION...

GULF OF MEXICO...

An upper-level trough extends from the NE corner of the Gulf of
Mexico, to an elongated upper=level low at 25N87W and
southwestward to the Yucatan Peninsula. Upper-level cyclonic flow
covers the Gulf of Mexico and surrounding coastal plains to the
east of the line that runs from coastal Alabama, to 26N92W, to the
coast of Mexico near 20N92W. Isolated showers and thunderstorms
are noted over just about the entire basin, except for scattered
moderate isolated strong convection from 24N to 28N west of 94W.

The gradient associated with a weak high pressure over the
soutehastern United States will maintain light to moderate winds
over the basin through Fri night. A surface trough will move
westward, off the coast of the Yucatan Peninsula each evening, and
it will dissipate in the SW Gulf of Mexico each morning. The
trough will be accompanied by moderate to fresh winds.

CARIBBEAN SEA...

Upper level cyclonic flow covers the Caribbean Sea to the NW of
the line that runs from NW Cuba to the Gulf of Honduras. Scattered
mdoerate to strong convection is seen from 14N to 22N between 80W
and 84W associated mainly with with a weak surface trough. The
disturbance is forecast to move slowly northwestward across the
northwestern Caribbean Sea and the Yucatan Peninsula over the next
couple of days with only slow development expected during that
time.

.Isolated showers and thunderstorms are elsewhere to the NW of
the line that runs from the Mona Passage to the east central coast
of Nicaragua.

The monsoon trough is along 09N74W in northern Colombia, beyond
10N in NW Costa Rica. Scattered mdoerate to strong convection
in clusters are observed from 09N to 11N between Colombia and
77W.

A relatively weak surface ridge in the western Atlantic Ocean
will maintain moderate to fresh trade winds in most of the region
through Monday night.

ATLANTIC OCEAN...

Please read the SPECIAL FEATURES section for details about
Hurricane Florence, Hurricane Isaac, and Hurricane Helene.

An upper level cyclonic circulation center is near 29N70W. A
surface trough is along 36N61W 34N62W 31N64W. Upper level cyclonic
wind flow also is from 30N northward from 77W westward. Isolated
moderate rainshowers are from 26N northward from 69W westward.

Hurricane Florence near 24.9N 58.9W 969 mb at 5 am EDT this
morning moving WNW at 8 kt. Maximum sustained winds 90 kt gusts
110 kt. Florence will move to near 25.4N 60.5W this afternoon,
26.1N 63.1W near tonight, 27.3N 66.2W near Tue afternoon, near
28.8N 69.3W Tue night, and 32.2N 74.8W Wed night. Florence is
forecast to become a major hurricane this morning, and is expected
to remain an extremely dangerous major hurricane through
Thursday. Florence will continue to 34.5N 78.1W Thu night, and
weaken to a tropical storm while moving inland to near 35.8N 79.6W
Fri night.

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

$$
Aguirre
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