[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111205
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 AM EDT Tue Sep 11 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 26.4N 64.1W at 11/0900 UTC or
355 nm S of Bermuda and about 850 nm ESE of Cape Fear North
Carolina moving WNW or 290 degrees at 13 kt. The estimated
minimum central pressure is 944 mb. The maximum sustained wind
speeds are 120 knots with gusts to 145 knots. Latest satellite
imagery shows scattered moderate to strong convection within
150 nm of the center in the NE quadrant, and within 120 nm of the
center in the SE quadrant. Scattered moderate convection is within
150 nm of the center in the SW quadrant, and within 180 nm of the
center in the NW quadrant. Florence is forecast to continue on a
west-northwestward to northwestward motion with a slight increase
in forward speed are expected during the next couple of days. On
the forecast track, the center of Florence will move over the
southwestern Atlantic Ocean between Bermuda and the Bahamas
through Wednesday, and approach the coast of North Carolina or
South Carolina on Thu. Interests elsewhere in the southeastern and
mid-Atlantic states need to monitor the progress of Florence.
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.

Tropical Storm Isaac is centered near 14.6N 48.1W at 11/0900 UTC,
which is about 765 nm E of the Lesser Antilles moving W or 270
degrees at 12 kt. The estimated minimum central pressure is 997
mb. The maximum sustained wind speeds are 60 knots with gusts to
75 knots. Latest satellite imagery shows scattered moderate
convection within 90 nm of the center, except within 120 nm of
the center in the SE quadrant. The present motion is expected
to continue through the end of the week. On this track,
Isaac should move across the Lesser Antilles and into the
eastern Caribbean Sea on Thu. Interest in the Lesser Antilles
should monitor the progress of Isaac. 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 16.0N 33.6W at 11/0900 UTC,
which is about 540 nm west of the southernmost Cabo Verde Islands
or 1365 nm south-southwest of the Azores moving WNW or 300
degrees at 12 kt. The estimated minimum central pressure is 968
mb. The maximum sustained wind speeds are 95 knots with gusts to
115 kt. Latest satellite imagery shows scattered moderate
convection within 120 nm of the center in the SE and NW quadrants
and within 150 nm of the center in the NE and S quadrants and
within 60 nm of the center in the SW quadrant. Scattered moderate
convection is Helene is forecast to maintain its present motion
with a decrease in forward speed through tonight. It is forecast
to then turn toward the the northwest and then north-northwest on
Wed and Thu. 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...

Tropical waves are not presently being analyzed.

...MONSOON TROUGH/ITCZ...

The monsoon trough is inland in Africa. The ITCZ is not analyzed
at this time. Isolated moderate to locally strong rainshowers are
elsewhere from 04N to 12N from 20W eastward, from 05N southward
between 20W and 27W, and from 10N southward between 30W and 60W.

...DISCUSSION...

GULF OF MEXICO...

A narrow upper-level trough extends from the northeastern part
of the Gulf of Mexico to the eastern central Gulf of Mexico and
to an upper-level low at 24N88W, It continues from the low to
inland the eastern Yucatan Peninsula. Associated upper cyclonic
flow is present south of 29N and east of 93W. Upper-level
anticyclonic wind flow covers the Gulf of Mexico west of 93W and
the Atlantic Ocean to 70W, and the Caribbean Sea from 15N
northward from 70W westward. Scattered moderate isolated strong
convection is occurring to the southeast of the upper-level low
over the southeastern gulf waters to the south of 25N east of
87W. Isolated showers and thunderstorms are elsewhere east of
91W. Please read the latest Tropical Weather Outlook under WMO
header ABNT20 KNHC, and under the AWIPS header MIATWOAT for more
details. The convection over southeastern Gulf of Mexico and the
northwestern Caribbean Sea is showing signs of organization, but
there are no signs of a surface circulation. Limited development
is anticipated today, but upper-level winds are forecast to become
more conducive, and a tropical depression could form on Thu or
Fri while the disturbance moves across the western Gulf of Mexico.
Interests across northeastern Mexico and the coasts of Texas and
Louisiana should monitor the progress of this system. Regardless
of development, heavy rainfall and gusty winds are likely over
western Cuba and portions of the northeastern Yucatan Peninsula
today.

A stationary front is just inland the Texas coast and SW
Louisiana. Plenty of deep atmospheric moisture is present over
the far western gulf as a rather strong upper trough moves across
central Texas. Scattered moderate isolated strong convection is
noted north of 22N west of 95W. Isolated showers and thunderstorms
are elsewhere west of 91W.

A surface trough in the western Caribbean Sea will move across
the Yucatan peninsula on Tue, and into the Gulf of Mexico on
Wed. The trough is expected to move into the western Gulf on
Thu and to the west of the area on Sat.

CARIBBEAN SEA...

A surface trough extends from the southeastern Gulf of Mexico,
through the Yucatan Channel and to a 1009 mb low over the Gulf of
Honduras at 17N87W. Latest satellite imagery shows numerous
moderate to strong convection north of 18N and west of 81W.
Scattered showers and isolated thunderstorms are elsewhere north
of 15N and west of 74W, including the Gulf of Honduras. The
numerous to strong convection is showing signs of organization,
but there are no signs of a surface circulation. Limited
development is anticipated today, but upper-level winds are
forecast to become more conducive, and a tropical depression could
form on Thu or on Fri while the disturbance moves across the
western Gulf of Mexico.

Tropical Storm Isaac near 14.6N 48.1W 997 mb at 5 AM EDT is
moving W at 12 kt. Maximum sustained winds 60 kt gusts 75 kt.
Isaac will move to 14.6N 50.1W this afternoon, then become a
minimal hurricane tonight near 14.6N 52.6W. Isaac will continue to
14.8N 55.0W Wed afternoon, then weaken back to a tropical storm
near 15.1N 57.6W by late Wed night. Isaac will continue weakening
as it tracks westward to near 15.5N 62.8W late Thu night, to near
15.6N 67.4W Fri night and to near 15.8N 72.0W Sat night. Expect
winds and seas to increase over the far eastern Caribbean
beginning late Wed into Thu.

ATLANTIC OCEAN...

Please refer to the Special Features section above for details
on Hurricanes Florence and Helene and on Tropical Storm Isaac.

An upper-level trough extends from an upper-level low at 30N35W
southwestward to 26N40W, where it becomes a cyclonic shear axis to
a small upper-level low dropping south at 26N48W and to near
23N55W. Upper-level cyclonic flow covers the area generally to the
north of 23N between 26W and 54W. Scattered moderate convection
is within 120 nm SE of the upper-level low at 26N48W, and within
60 nm of the upper-level low at 30N35W. Isolated showers and
thunderstorms are from 22N to 24N between 44W and 50W. Isolated
showers and thunderstorms are elsewhere west of 40W.

Hurricane Florence near 26.4N 64.1W 944 mb at 5 AM EDT kt is
moving WNW at 13 kt. Florence will remain an extremely dangerous
major hurricane through Thursday. Maximum sustained winds 120 kt
gusts 145 kt. Florence will move to 27.2N 66.4W this afternoon,
28.7N 69.4W tonight, 30.5N 72.2W Wed afternoon, pass N of the area
near 32.2N 74.5W Wed night, then approach the Carolina coast near
34.3N 77.1W Thu night.

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

$$
Aguirre
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