[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 060605
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
205 AM EDT Thu Sep 6 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 22.7N 46.6W at 06/0300 UTC,
which is about 945 nm ENE of the northern Leeward Islands or 1075
nm ESE of Bermuda moving NW at 9 knots. The estimated minimum
central pressure has risen slightly to 956 mb. The maximum
sustained winds have diminished slightly to 110 kt with gusts to
135 kt. Florence has weaken some over the past few hours as
noted in its now asymmetric cloud pattern compared to the very
very symmetrical cloud pattern it revealed Wed evening. Southwesterly
shear is affecting the tropical cyclone. The eye appears rather
small, about 15 nm in diameter, and it is not as clear as it was
a few hours ago. The conventional IR imagery and water vapor
imagery reveal cirrus clouds fanning outward over the NW
semicircle. Latest imagery shows scattered moderate isolated
strong convection within 180 nm of the center in the NE quadrant,
and within 120 nm of the center in the NW quadrant. The latest
NHC advisory forecasts Florence to continue in its present motion
through today, before it turns to the west-northwest tonight as
it weakens. Public Advisories for Florence are issued under
WMO/AWIPS headers WTNT31 KNHC/ MIATCPAT1. Forecast Advisories for
Florence are issued under WMO/AWIPS headers WTNT21 KNHC/MIATCMAT1.

Tropical Depression Gordon is weakening over western Mississippi.
At 06/0300 UTC, it is centered near 33.2N 91.0W, which is about
80 miles NW of Jackson. It is moving NW, or 320 degrees at 8
knots. The estimated minimum central pressure is 1013 mb. The
maximum sustained wind speeds are near 20 kt with higher gusts.
The threat continues for heavy rain as Gordon is expected to
produce total rain accumulations of 2 to 4 inches over portions of
western Mississippi, southern and western Arkansas, and from
western to northern Missouri into adjacent parts of Illinois with
isolated maximum amounts of 6 inches through early Sat This
rainfall will cause flash flooding across portions of these areas.
Isolated showers and thunderstorms are north of 28N between
between 85W and 88W. Future information on Gordon can be found in
Public Advisories issued by the Weather Prediction Center under
AWIPS header TCPAT2, WMO header WTNT32 KWNH, and on the web at
https://www.wpc.ncep.noaa.gov. For specific local information on
Gordon for the affected states, please refer to products issued by
your located National Weather Service office.

A tropical wave has its axis along 29W from 03N to 20N. It is
moving westward at 10 to 15 kt. A 1008 mb low pressure center is
analyzed on the wave axis at 13N29N. Earlier deep convection
associated with this system has decreased over the past few hours.
Latest satellite imagery shows scattered strong convection within
150 nm of the low in the N quadrant, and within 60 nm of the low
in the NW quadrant. Scattered moderate convection is within 30 nm
of 15N32W and within 30 nm of 13N32W. Environmental conditions
are forecast to be increasingly conducive for additional
development, and a tropical depression is expected to form during
the next few days while the system moves west-northwestward
across the tropical Atlantic Ocean. The chance of this system
becoming a tropical cyclone during the next 48 hours is high.
Please read the latest NHC Tropical Weather Outlook under
AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more information.

...TROPICAL WAVES...

A tropical wave is well inland the coast of western Africa. In
advance of this tropical wave, large clusters of scattered
moderate to strong convection are just offshore the coast of
Africa from Sierra Leone to northern Senegal and well inland the
coast between these two locations. The tropical wave is forecast
to move off the west coast of Africa on Fri.

A western Caribbean Sea tropical wave has its axis along 86W
south of 21N to across central Honduras and western Nicaragua, and
continues southward to the eastern Pacific near 05N, moving
westward at 10 to 15 kt. Scattered moderate convection is within
60 nm either side of the wave over Honduras. Similar type
convection moving westward is east of the wave from 20N to 22N.
Isolated showers and thunderstorms are elsewhere within 60 nm
either side of the wave.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coastal sections of
Mauritania near 19N16W, to the 1008 mb low that is associated with
the Special Features section tropical wave along 29N. It
continues from this system to 08N38W. The ITCZ extends from
08N38W to 07N46W to 07N52W. Outside convection described with the
Special Features tropical wave and low along 29W, only scattered
moderate isolated strong convection is seen north of the monsoon
trough within 30 nm of a line from 11N33W to 11N36W. Scattered
strong convection is over the far eastern Atlantic offshore the
coast of Africa within 45 nm either side of a line from 10N16W to
10N21W.

...DISCUSSION...

GULF OF MEXICO...

Upper-level cyclonic wind flow, with an inverted trough, covers
the western one-third of the Gulf of Mexico. Upper level
anticyclonic wind flow, with a ridge, covers the rest of the Gulf
of Mexico. Scattered moderate isolated strong convection is
concentrated over the western gulf to the west of 94W and south of
27N. Isolated showers and thunderstorms are elsewhere across the
gulf.

A weak surface ridge will build from the Carolinas to the coast
of Texas in the wake of Gordon. Expect gentle to moderate easterly
winds and modest seas into early next week. The exception will be
fresh winds pulsing off the west coast of the Yucatan Peninsula,
mainly during the late evening hours, due to a daily trough that
sets up in the SW corner of the Gulf of Mexico.

CARIBBEAN SEA...

Upper level cyclonic wind flow covers the Caribbean Sea to the
west of the line that runs from Puerto Rico to La Peninsula de la
Guajira of northern Colombia. Isolated moderate to locally strong
rainshowers are in the area of upper level cyclonic wind flow.

The easternmost part of the eastern Pacific monsoon trough is
along 09N/10N from 74W in Colombia beyond western sections of
Costa Rica. Scattered showers and thunderstorms are seen from
10N to 12N between the coast of Colombia and 78W.

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

ATLANTIC OCEAN...

Please read the Special Features section above for details about
Hurricane Florence. A second area of interest pertains to a
broad area of low pressure in the far eastern Atlantic. It has
a high chance of tropical cyclone formation during the next 48
hours.

An upper-level trough extends from near Bermuda to a westward
moving broad upper-level low at 25N74W, and southwest to the
Windward Passage. From there it continues to Nicaragua and Costa
Rica and to southwestern Caribbean Sea. Upper-level cyclonic flow
covers the Atlantic Ocean from the Greater Antilles northward
from 60W westward. A surface trough is analyzed from near 31N69W
to the southeastern Bahamas. Another surface trough is analyzed
from near 30N61W to 23N65W. Satellite imagery shows an area of
scattered showers and thunderstorms concentrated from 24N to 30N
between 67W and 76W. Scattered showers and thunderstorms are also
seen from 22N to 24N between 72W and 77W.

A weak pressure pattern will maintain gentle to moderate easterly
winds across the area through Sun night. Easterly swell from
Hurricane Florence will move into the open waters east of the
Bahamas from through Sun.

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

$$
Aguirre
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