[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 160005
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 PM EDT Sat Sep 15 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 1800 UTC surface analysis and satellite imagery through
2345 UTC.

...SPECIAL FEATURES...

Tropical Storm Florence is centered near 33.6N 80.1W at 16/0000
UTC, or about 40 nm SSW of Florence South Carolina moving W at 2
kt. Estimated minimum central pressure is 997 mb. Maximum
sustained wind speed is 40 kt with gusts to 50 kt. Satellite
imagery shows scattered moderate isolated strong convection within
210 nm of the center over the SE quadrant. Scattered moderate
convection is within 90 nm of the center in the NW quadrant, and
also within 60 nm of line from 34N75W to 36N76W. Latest NHC
advisory has Florence turning toward the west-northwest on Sun,
before turning northward over the Ohio Valley on Mon. See the
latest NHC forecast/advisory under AWIPS/WMO headers
MIATCPAT1/WTNT31 KNHC for more details.

Tropical Storm Helene is centered near 40.4N 31.4W at 16/0000
UTC, or 60 nm NNW of Flores Island in the western Azores, moving
NE at 21 kt. Estimated minimum central pressure is 989 mb. Maximum
sustained wind speed is 55 kt with gusts to 65 kt. Helen is
undergoing vertical shear as the low-level is visible. Scattered
moderate isolated strong convection is removed from the center
over the NE quadrant from 40N to 42n between 28W and 31W.
Scattered moderate convection is from 30N.5N to 42W between 25W
and 29W. Helene is forecast to continue with an increase in
forward speed during the next couple of days. On the current
forecast track, Helene should pass near or over the western Azores
tonight and then approach Ireland and the United Kingdom Sunday
night and Mon. See the latest NHC forecast/advisory under
AWIPS/WMO headers MIATCPAT3/WTNT33 KNHC for more details.

Tropical Storm Joyce is centered near 33.1N 39.6W at 15/2100 UTC
or 680 nm WSW of the Azores moving ENE at 15 kt. Estimated minimum
central pressure is 1002 mb. Maximum sustained wind speed is 40
kt with gusts to 50 kt. Latest satellite imagery shows that the
center is exposed, with scattered moderate isolated strong
convection removed within 90 to 240 nm over the center in the NE
quadrant. Joyce is forecast by the latest NHC advisory to continue
on its current motion over the next day or so. The storm should
turn back to the east on Mon and to the southeast on Tue, away
from the Azores .See the latest NHC forecast/advisory under
AWIPS/WMO headers MIATCPAT5/WTNT35 KNHC for more details.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis extending from
near 05N33W to 13.5N34.5W to near 20N35W, moving westward at
10-15 kt. The wave is surrounded by a rather dry environment,
which is inhibiting deep convection from forming along or near it.
Only scattered showers showers and thunderstorms are within 120 nm
either side of the wave axis from 05N to 08N.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from 14N17W to 12N22W to 10N30W.
The ITCZ extends from 07N34W to 08N48W to 06N58W. Aside from the
shower and thunderstorm associated with the above described tropical
wave, scattered moderate isolated strong convection is within 180
nm north of the ITCZ between 45W and 50W, and within 60 nm south
of the ITCZ between 51W and 53W. Scattered moderate convection is
within 60 nm north of the ITCZ between 38W and 41W, and within 90
nm south of the ITCZ between 44W and 46W. Similar activity is
northwest of the ITCZ within 30 nm of line from 10N55W to 09N59W.

...DISCUSSION...

GULF OF MEXICO...

A 1014 mb surface high is centered near 27N88W. Tropical Storm
Florence is centered to the northeast of the basin enhancing the
pressure gradient some across the east Gulf waters. With this,
moderate westerly flow prevails north of 28N and east of 86W. To
the west, a surface low centered over southern Texas is enhancing
scattered to numerous moderate convection north of 21N and west of
95W. An upper-level low is centered just northeast of the Yucatan
Peninsula. Scattered showers and isolated thunderstorms are south
of 26N between 90W and 95W, while isolated showers and
thunderstorms are south of 27N east of 90W.

CARIBBEAN SEA...

A 1006 mb low over the central Caribbean is centered near
16.5N72W. It is part of broad area of low pressure associated with
the remnants of Isaac. Scattered showers and thunderstorms with
this area of low pressuer are observed from 13N to 18N between 65W
and 75W. This area of low pressure is forecast to bring locally
heavy rains and gusty winds across portions of Hispaniola,
Jamaica, and eastern Cuba during the next couple of days.
An upper-level cyclonic circulation center is noted just east of
the northeastern side of the Yucatan Peninsula. Isolated showers
and thunderstorms are seen north of 15N between 81W and 86W. Over
the far southwestern Caribbean, the eastern extent of the eastern
Pacific monsoon trough is helping to trigger off scattered
showers and isolated thunderstorms south of 13N from northwestern
Colombia westward to across much of Costa Rica and Panama. Moderate
to fresh winds prevail with this low over the central Caribbean.
Elsewhere, gentle to moderate trades prevail east and west of the
low. Strong nocturnal trades are forecast off the northwest coast
of Colombia on Mon and Tue nights.

ATLANTIC OCEAN...

Please refer to the Special Features section above, for details
on Tropical Storms Florence, Helene, and Joyce.

An upper-level trough extends across the central Atlantic. A 1011
mb low is near 30N63W, with a trough to its northeast along 31N
between 54W and 60W. Scattered moderate convection is seen within
240 nm southeast of the low, and north of 30N between 50W and 60W.

A surface ridge will remain about stationary from near 32N68W to
southeastern Florida through the weekend. The ridge will shift
northward by the middle of the next week.

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

$$
Aguirre
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