[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 271204
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
804 AM EDT Thu Sep 27 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
1130 UTC.

...SPECIAL FEATURES...

The center of Tropical Storm Kirk at 27/1200 UTC is near 13.6N
58.7W, or about 95 km ENE of Barbados or about 275 km ESE of
Martinique. KIRK is moving WNW or 290 degrees 14 knots. The
estimated minimum central pressure has risen to 1000 mb. The
maximum sustained wind speeds are 45 knots with gusts to 55 knots.
Scattered to numerous strong rainshowers are from 12N to 15N
between 54W and 58W. Kirk remains under vertical shear as noted
by its center being displaced from the deep convection. The
latest NHC advisory keeps Kirk moving in its current motion over
the over the next few days. On the present forecast track, the
center of Kirk will move across the Lesser Antilles within the
tropical storm warning area by this evening. Kirk is expected to
produce very heavy rain across the northern Windward and southern
Leeward Islands from Thursday through much of Friday. It is
possible that these rains may produce life-threatening flash
floods and mudslides. Please read the latest NHC
Forecast/Advisory under AWIPS/WMO Headers MIATCMAT2/WTNT22 KNHC
for more details.

Post-Tropical Cyclone Leslie is in the central Atlantic Ocean,
several hundred miles west of the Azores. It remains a powerful
non-tropical low pressure center, with hurricane-force winds. The
associated rainshower activity gradually is becoming more
organized, and Leslie is expected to become a subtropical storm
again, or possibly a tropical storm, later today or Friday while
it moves west-southwestward 10 mph in the north central Atlantic
Ocean. The chance of formation into a tropical cyclone during the
next 48 hours is high. Please read the HIGH SEAS FORECAST, AWIPS
header NFDHSFAT1, WMO header FZNT01 KWBC, and on the Web at
https://ocean.weather.gov/shtml/NFDHSFAT1.shtml., for more
details.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis along 27W from
03N to 19N, moving westward at 10 to 15 kt. Total precipitable
water (TPW) imagery clearly indicates a maximum in low-level
moisture to the east of this wave. 700 mb guidance from the GFS
model has a sharp 700 mb inverted trough over the wave. Isolated
showers and thunderstorms are seen within 180 nm east of the wave
from 06N to 09N, and also from 14N to 19N.

A rather ill-defined central Atlantic tropical wave has its axis
near 38W from 03N to 19N, moving westward at 15 kt. 700 mb
guidance from the GFS model depicts a broad 700 mb trough over
the environment of this wave. Recent mid-level satellite winds
reveal a broad inverted trough over the wave, with winds shifting
from northeast to southeast across the wave axis. Based on the
current signature status of this wave in model guidance and
in satellite animation, low confidence can be expected in
tracking this wave for the next several days. Isolated
showers and thunderstorms are in the vicinity of where the wave
axis intersects the ITCZ, roughly from 05N to 08N between 37W and
40W.

A tropical wave has its axis along 75W south of 19N, moving
westward at 15 kt. Scattered showers and isolated thunderstorms
are noted within 120 nm west of the wave south of 13N. Isolated
showers and thunderstorms are within 120 nm either side of the
wave north of 13N.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis briefly extends off the coast of Africa
over Guinea Bissau to near 11N12W. It resumes at 11N24W to 08N30W,
where it transitions to the ITCZ to just west of the tropical
wave near 38W, and resumes west of the same wave at 07N39W
to 06N47W. Outside of the convection mentioned with the two
tropical waves, scattered moderate convection is within 120 nm
south of the ITCZ between 43W and 45W and within 60 nm north of
of the ITCZ between 39W and 41W.

...DISCUSSION...

GULF OF MEXICO...

Earlier scattered moderate convection that was over the much of
the northwestern Gulf has diminished, except recent radar data
shows new scattered new scattered moderate isolated strong
convection developing ahead of a cold front that is over eastern
Texas. This activity is expected to push further into the
northwestern Gulf waters through early this morning. Some of the
activity may produce strong gusty winds and frequent lightning.
The cold front will become stationary along the Texas coast this
morning. Scattered showers and thunderstorms are elsewhere west of
89W, while isolated showers and thunderstorms are east of 89W.

Surface high pressure, that is to the NE of the area, will
support gentle to moderate E to SE winds, and sea heights of 4
feet or less, across most of the region through Sunday.

CARIBBEAN SEA...

Instability generated by the eastern Pacific monsoon trough that
protrudes into the far southwestern Caribbean, along with pretty
decent upper-level ventilation continues to allow for scattered
showers and thunderstorms to continue over much of the southwestern
Caribbean south of 14N and west of 77W. Scattered showers and
isolated thunderstorms are over much of the northwestern
Caribbean, and also south of 16N east of 70W, including the
vicinity of Trinidad and Tobago.

Tropical Storm Kirk near 13.5N 58.3W 1002 mb at 5 AM EDT moving
WNW at 14 kt. Maximum sustained winds 45 kt gusts 55 kt. Kirk will
move across the Lesser Antilles today, then weaken to a tropical
depression in the eastern Caribbean Fri, and become a remnant low
south of Hispaniola. Fresh to strong trade winds are expected in
the south-central Caribbean Sea today.

ATLANTIC OCEAN...

A strong cold front and an associated area of gale force winds
extend southward from Post-Tropical Cyclone Leslie, which is
centered well north of the area near 36N39W with a pressure of 978
mb. It is producing hurricane force winds. The cold front enters
the forecast area near 31N33W, and extends southwestward to 25N40W
to 23N50W to 25N59W, then is weakening northwestward to 27N66W. A
pre-frontal trough extends from near 25N36W to 20N43W. Satellite
imagery shows scattered moderate convection along and within 75 nm
east of the front north of 28N, and within 60 nm to the south of
the front between 56W and 66W. Similar convection is along and
within 60 nm north of the front between 44W and 52W. Isolated
showers are along and near the pre-frontal trough. The cold front
is forecast to become stationary from near 29N35W to 23N44W and to
near 21N51W by this afternoon and dissipate by early Fri
afternoon. Large swell generated by Post-Tropical Cyclone Leslie
is expected to spread east of 75W by Fri night, and continue
through the weekend. Post-Tropical Cyclone Leslie is forecast to
again become a tropical or subtropical storm during the next
couple of days. More details are described above under the Special
Features section.

Surface high pressure will build southward across the west-central
Atlantic Ocean today. Large swell, that is being generated by an
intense north central Atlantic Ocean low pressure system, is
expected to spread east of 75W by Friday night, and continue
through the weekend.

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

$$
ja/dm/mt
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