[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 260945
TWDAT

Tropical Weather Discussion...UPDATED
NWS National Hurricane Center Miami FL
545 AM EDT Wed Sep 26 2018

Updated the Special Features section to include mention of
Tropical Storm Kirk

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
0930 UTC.

...Special Features...Updated

The earlier remnants of Kirk have regenerated back into a
tropical storm as of 0900 UTC this morning. At 0900 UTC Tropical
Storm Kirk is centered near 11.8N 52.7W, which is about 405 nm
east of Barbados or 515 nm ESE of Martinique, moving westward at
16 kt. The estimated minimum central pressure is 1004 mb. The
maximum sustained wind speed is 40 kt with gusts to 50 kt. Latest
satellite imagery shows that deep convection of the numerous
moderate to strong type intensity has increased near the center of
the tropical cyclone, while at the same time it has gradually
become symmetrical during the past few hours. This convection is
observed within 120 nm of the center in the SE semicircle and
within 90 nm of the center in the NW semicircle. Scattered
moderate isolated strong convection is to the northeast of
Kirk from 14N to 16N between 49W and 52W, and from 10N to 13N
between 53W and 56W. The latest NHC advisory has Kirk moving in a
westward to west-northwestward motion through Fri night. On this
forecast track, Kirk is expected to approach Barbados and the
northern Windward Islands Thu afternoon and move into the eastern
Caribbean Sea by Fri morning. Little change in strength is
forecast until Kirk moves through the central Lesser Antilles Thu
afternoon and evening. Rapid weakening is expected on Fri after
Kirk emerges over the Caribbean Sea. See latest NHC Forecast/Advisory
under AWIPS/WMO Headers MIATCMAT2/WTNT22 KNHC for more details.

Post-Tropical Cyclone Leslie is currently centered about 740 nm
west-southwest of the Azores Islands. It is producing gale force
winds. Scattered moderate isolated strong convection is seen from
28N to 33N between 37W and 41W. Scattered moderate convection is
from 33N to 38N between 38W and 42W. Leslie is expected to
reacquire subtropical or tropical characteristics on Thu or Fri
while the cyclone meanders over the north-central Atlantic. There
is a medium chance of of this system becoming a tropical cyclone
during the next 48 hours. For more information on this system,
see High Seas Forecasts issued by the National Weather Service.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis along 22W from
03N to 17N, moving westward at 10 to 15 kt. Model guidance
depicts a broad 700 mb trough over and near this wave. The
satellite-derived low to mid-level nicely display a NE to SE
wind shift across the wave. Satellite imagery shows  Isolated
showers and thunderstorms are within 150 nm west and 120 nm east
of the wave axis from 11N to 14N.

A tropical wave has is its axis along 50W, with a 1006 mb low on
it near 12N60W. This system is described under the Special
Features section above.

A tropical wave has its axis along 60W south of 19N, moving
westward at 15 kt. This wave is shrouded in a very moist and
unstable environment as observed in satellite imagery and in the
Total Precipitable Water (TPW) satellite animation where it shows
a broad pool of moisture. The moisture is noted to be in the form
of multilayer clouds, with scattered showers and thunderstorms
along the wave, and within 240 nm west of the wave south of 15N.
are underneath these clouds from 08N to 15N between 57W and 62W,
including the Windward Islands. This activity will continue
through at least early this afternoon as a very moist upper
southerly flow remains in place across the eastern Caribbean.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends off the coast of Africa over
Senegal at 13N17W and continues to 10N22W to 08N26W, where latest
scatterometer data indicated the ITCZ begins and continues to
07N31W to near 07N42W. Outside of the convection mentioned with
the two tropical waves and the remnants of Kirk, scattered
moderate convection is within 90 nm north of the ITCZ between
28W-34W. Scattered moderate isolated strong convection is within
90 nm north of the ITCZ between 35W-38W and within 60 nm north
of the ITCZ between 26W-28W. Scattered moderate convection is
within 60 nm south of the ITCZ between 31W-33W.

...DISCUSSION...

GULF OF MEXICO...

A very moist and unstable air mass along with upper-level
diffluence over the north-central Gulf Coast resulted in
scattered showers and isolated thunderstorms north of 27N between
84W-90W last night. This activity has since dissipated.
Scattered showers and thunderstorms moving westward are  over the
eastern Gulf from 26N to 29N east of 84W to the Florida coast.
This activity fired up yesterday evening along the Florida west
coast sea breeze boundary. It has pushed into the eastern Gulf,
and is quickly weakening.

A thermal trough over the east-central Bay of Campeche is
weakening and is no longer producing any significant shower
activity. A surface trough will develop over the Yucatan
peninsula each evening, shift W over the SW Gulf each night,
then dissipate each morning. Elsewhere across the Gulf, gentle
to moderate winds will increase to between moderate and fresh
during the second half of this week as high pressure builds N of
the region.

CARIBBEAN SEA...

Scattered showers and thunderstorms ahead of a tropical wave that
is approaching the Windward Islands have moved into the far
eastern Caribbean, and are south of 17N east of 64W to across
the Windward Islands. Isolated showers and thunderstorms are
elsewhere over the eastern Caribbean. Instability generated by
the eastern Pacific monsoon trough that protrudes into the far
southwestern Caribbean, along with low-level speed convergence
and to some extent a weak upper low near 12N80W, which is at the
base of an upper trough, has recently resulted in a rapid increase
of scattered showers and thunderstorms within 60 nm of a line
from 09N78W to 12.5N82W to inland the northeast section of
Nicaragua from 13N to 15N between 82W and 85W. Scattered moderate
convection over the interior sections of Honduras and Nicaragua
have just about all diminished. The earlier heaviest part of this
activity has shifted to the western sections of these countries.
Expect fresh to strong winds over the central Caribbean through
midweek, with moderate to fresh winds thereafter through Friday.

ATLANTIC OCEAN...

Currently, there is one tropical waves in the tropical Atlantic
and one in the Caribbean Sea. There is newly regenerated Tropical
Storm Kirk also in the tropical Atlantic. For information on
those features, please read the Special Features and Tropical
Waves sections above.

A surface trough is analyzed from just south of a developing
hurricane force wind warning 1000 mb low pressure at 33N43W, south
to 26N45W to 24N50W and to 20N60W. Scattered moderate isolated
strong convection is within 90 to 120 nm east of the trough north
of 25N.

Another surface trough extends from 28N29W to 22N30W. Only
isolated showers are within 60 nm of the trough. Otherwise,
ridging over the northeast Atlantic is helping to maintain
generally stable and create fair weather north of 20N and east of
30W.

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

$$
Aguirre
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