[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201100
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
700 AM EDT Mon Apr 20 2020

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
1045 UTC.

...SPECIAL FEATURES...

Atlantic Gale Warning: A cold front will enter the waters east of
northern Florida this afternoon, then cross the waters N of 22N
through Wed evening. Fresh to strong southerly winds will precede
this front north of 27N beginning early this morning and increase
to gale force in deep convection north of 29N by mid to late
morning today. The gale force winds are forecast to lift north of
the area by this evening. Then winds in the vicinity of the front
will diminish to fresh to strong speeds as the front shifts E.
Seas of 9 to 12 ft can be expected in the gale force wind area
north of 29N between 70W-80W late this morning into this evening.
Please see the High Seas Forecast under AWIPS/WMO headers
MIAHSFAT2/FZNT02 KNHC or at website
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends southwestward from the coast of
Sierra Leone on the coast of Africa near 07N12W to 01N22W, where
overnight scatterometer data indicates that it transitions to the
ITCZ and continues to 02N35W and to 01N50W. Scattered moderate
to isolated convection is within 120 nm northwest of the trough
between 12W-14W, within 60 nm northwest of the trough axis
between 15W-18W and within 60 nm south of the ITCZ between 24W-
28W. Scattered moderate convection is within 180 nm north of the
ITCZ between 23W-27W, and also north of the ITCZ within 30 nm of
line from 03N30W to 04N33W and to 05N36W.

An area of scattered moderate to strong convection is observed
from 01N to 07N and west of 49W to the coast of Brazil.

GULF OF MEXICO...

As of 09Z, a cold front has pushed southward into the northern
Gulf waters. It is analyzed along a position from Cape San Blas
in the Florida panhandle to just south of the Mississippi Delta
and west-northwest from there to just east of Galveston, Texas.
A rather potent squall line racing southeastward is out ahead of
the front from Apalachee Bay to near 28N87W, while a rather
vigorous mid-level shortwave trough advances eastward over the
western Florida panhandle. This along with plenty atmospheric
instability in place along with a strong low-level jet has lead
to the overnight development of strong to severe thunderstorms
along and within 60 nm southeast of the squall line. This
activity is capable of producing strong and damaging winds as
well as frequent lightning strikes and very rough seas as they
race southeastward during the morning hours today. Otherwise, a
surface ridge extends from western Cuba to the central Gulf of
Mexico. Overnight Ascat data indicates fresh to locally strong
southwest winds over the north- central Gulf, with fresh
southeast winds farther south near the Yucatan Peninsula. Gentle
winds are present over the western Gulf.

The forecast calls for the aforementioned cold front to reach
the east-central Gulf this afternoon while weakening, with
fresh to strong southerly winds ahead of it diminishing to
mainly fresh speeds. Scattered showers and thunderstorms with the
preceding squall line will continue southeastward to the east-
central Gulf this morning. The next cold front is forecast to
approach the NW Gulf Wed night into Thu morning. Fresh to strong
winds are forecast to develop ahead of the front over the western
half of the Gulf by Tue night. The front will reach from near
Cross City, Florida to 28N90W by Fri morning. Otherwise, smoke
from agricultural fires in southern Mexico could reduce visibility
in the SW Gulf.

CARIBBEAN SEA...

Mid to upper-level ridging and associated strong subsidence will
maintain dry and stable weather conditions across the majority
of the basin for the next few days. There are presently two
exceptions. The first is in the eastern Caribbean, including the
vicinity of Puerto Rico and the Leeward Islands, where patches of
low-level moisture in the form of mainly broken low clouds are
noted moving quickly westward in the trade wind flow. Scattered
shower activity is present with some of this moisture. The other
exception is in the northwest Caribbean, where isolated showers
are seen between the northeast coast of Honduras to just south of
Jamaica and to east-central Cuban coast. Overnight Ascat data
shows fresh trade winds in the central Caribbean, except locally
strong near the coast of Colombia. Fresh wind speeds are also
present from the Yucatan Channel to the coast of Honduras, with
strong east winds within 60 nm of the north coast of Honduras.
Moderate trade winds are present elsewhere.

The forecast calls for high pressure north of the area to maintain
fresh to strong winds in the south-central Caribbean and the Gulf
of Honduras through Fri night. Mainly moderate to fresh winds are
expected elsewhere during the entire period. Otherwise, smoke
from agricultural fires in Central America could reduce visibility
near the Yucatan Peninsula and offshore of Belize and Honduras.

ATLANTIC OCEAN...

A warm front extends southeastward from a 1004 mb low near
Cape Hatteras, North Carolina to Wilmington where it transitions
to a warm front that stretches southwestward to the Georgia/Florida
border and northwestward from there to a 1008 mb low over west-
central Alabama. Very active strong to severe shower and
thunderstorm activity occurring over most of the southeastern
U.S. has moved offshore the coast from just north of northeastern
FLorida to the southern section of South Carolina. Similar
activity, of scattered moderate to isolated strong intensity, has
moved farther offshore, and is noted from along the coast from
30N to 33N, east to near 69W. This activity is under an area
of upper-level diffluence that is helping to sustain it. As the
mid-level shortwave trough, that is currently over the western
Florida panhandle, continues eastward along with a cold front, it
will act to push the shower and thunderstorms activity to east
and northeast of the southeastern U.S. coast during this
afternoon.

Overnight Ascat data passes depict fresh to locally strong
southerly winds north of 29.5N between 72W-77W. Strong to gale
force winds are seen north of 30.5N in the same area. The 06Z
synoptic analysis has a cold front extending from near 32N49W
southwestward to 28N56W and to 26N65W, where it transitions to a
warm front northwestward from there to north of the area at
32N72W. Broken to overcast low and mid-level clouds along with
isolated showers and thunderstorms are noted within 120 nm east
of the cold front north of 29N. Broken low clouds with isolated
showers are along and within 120 nm southeast and south of the
cold front from 27N to 29N. Farther east, another cold front with
no significant convection or wind is along a position from 32N20W
to 29.5N31W where it becomes stationary to 32N56W and a warm front
northwestward from there to a triple point well north of the
area. A 1026 mb high center is analyzed well north of the area
near 35N30W and a 1019 mb high center is analyzed near 31.5N63W.
Ridging associated to both of these features is maintaining gentle
to moderate east winds over much of the Atlantic from 15N-28N and
between 35W and the Bahamas.

For the forecast west of 65W, the western segment of the cold
front extending from 32N49W to 28N56W and to 26N65W will pull
away from 65W during this morning as the warm front lifts north
of the area. A second cold front, as mentioned in the first
paragraph, will move over the waters east of northern Florida
this afternoon, and a Gale Warning is in effect for the waters
north of 29N and between 70W-80W as southerly winds ahead of this
front significantly increase in response to a very strong low-
level jet that will shift from the Gulf of Mexico to east of
northern Florida and the southeastern U.S. See the Special
Features section above for details. Another cold front will move
across the SE U.S. on Thu with strong to possibly near gale force
southerly winds developing ahead of the front over the waters east
of northern Florida.

$$
Aguirre
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