[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 170921
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Tue Nov 17 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
0900 UTC.

...SPECIAL FEATURES...

Hurricane Iota is centered near 13.7N 84.3W at 17/0900 UTC or 10
nm ENE of El Pia Nicaragua moving W at 8 kt. Estimated minimum
central pressure is 950 mb. Maximum sustained wind speed is 90
kt with gusts to 110 kt. Iota is moving toward the west and this
general motion is expected to continue during the next day or so.
On the forecast track, Iota will move farther inland across
northern Nicaragua today, and move across southern Honduras
tonight and Wednesday. Additional rapid weakening is expected
today into Wednesday, and Iota is forecast to dissipate over
Central America by Wednesday night. Numerous moderate to strong
convection is noted within 210 nm of the center of Iota. Scattered
moderate and isolated strong convection is noted elsewhere within
360 nm in the N semicircle and 270 nm in the SW quadrant of Iota.
Life-threatening flash flooding and river flooding is expected
through Thursday across portions of Central America due to heavy
rainfall from Iota. Flooding and mudslides across portions of
Honduras, Nicaragua and Guatemala could be exacerbated by Hurricane
Eta’s recent effects there, resulting in significant to potentially
catastrophic impacts. Please refer to statements issued by your
national meteorological service for more details on the rainfall
and flooding threats. Please read the latest NHC Public Advisory
at https://www.nhc.noaa.gov/text/MIATCPAT1.shtml and
Forecast/Advisory at https://www.nhc.noaa.gov/text/MIATCMAT1.shtml
for more details.

Gulf of Mexico Gale Warning: Strong autumn high pressure will
build southward across the Gulf of Mexico behind a cold front
that extends from near Fort Myers, Florida to the southern Bay of
Campeche. The high pressure will create a very tight gradient
between it and the front by this evening. This synoptic set-up is
forecast to lead to strong northeast winds, with frequent gusts to
gale force over the southeastern half of the Gulf waters,
including the Straits of Florida and waters adjacent to the
Yucatan Channel starting this evening, 18/0000 UTC through
Wednesday night. Expect building seas 12 to 16 ft across this
area with very hazardous conditions between the wind waves against
the flow of the gulf stream through the Straits of Florida, and
due to SE swell generated by Iota which will move through the
Yucatan Channel. Please read the latest NWS High Seas Forecast
issued by the National Hurricane Center at website
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details.

Caribbean Gale Warning: The same conditions that will occur in the
southeastern half of the Gulf of Mexico will spread into the far
NW Caribbean with gusts to gale force possible behind the cold
front and N of 20N Wed and Wed night. The cold front will stall
from eastern Cuba to the Gulf of Honduras early Thu. Large and
hazardous seas are expected in the Gulf of Honduras and approach
to the Yucatan Channel today through Wed night as fresh northerly
wind waves behind the front mix with swells generated by Iota.
Please read the latest NWS High Seas Forecast issued by the
National Hurricane Center at website
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details.

Atlantic Gale Warning: The pressure gradient which will lead to
frequent gusts to gale force over the southeastern Gulf of Mexicoand far NW Caribbean Sea will also bring frequent gusts to the
western Atlantic off the coast of South Florida and the Bahamas.
These gusts will begin by Wednesday evening, 19/0000 UTC through
Thu offshore of the Bahamas, and through Thu night from 22N-27N
and E of 70W. Expect seas to build 8 to 11 ft, except up to 14 ft
across the gulfstream approach to the Straits of Florida where
conditions will be very hazardous. Please read the latest NWS
High Seas Forecast issued by the National Hurricane Center at
website https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more
details.

...TROPICAL WAVES...

The axis of a tropical wave is near 32W from the equator to 14N,
moving westward at 10-15 kt. Scattered moderate convection is
noted from 07N-09N between 29W-32W.

The axis of a tropical wave is near 55W/56W from central Suriname
to 18N, moving westward at 10-15 kt. Scattered moderate to
isolated strong convection is noted from 07N-13N between 51W-56W.

The axis of a tropical wave is near 67W/68W from near the Mona
Passage to western Venezuela, moving westward at 5-10 kt.
Scattered moderate and isolated strong convection is noted from
11N-14N between 66W-71W, with additional convection inland and
across the ABC Islands.

...MONSOON TROUGH/ITCZ

The monsoon trough axis extends from the coast of Africa near the
border of Guinea and Sierra Leone to 08N18W. The ITCZ axis continues
from 08N18W to 06N31W then continues west of a tropical wave near
06N33W to the coast of Brazil near 01N51W. Scattered moderate and
isolated strong convection is along the ITCZ from the equator to
06N between 19W-40W, with similar convection from 04N-07N between
40W-53W.

GULF OF MEXICO...

See Special Feature section above for details on a Gale Warning in
effect over the southeastern half of the Gulf of Mexico.

Ahead of the cold front mentioned above, overnight scatterometer
data showed mainly moderate NE-E flow. SE swell associated with
Hurricane Iota, situated well SE-S of the basin, is already
spreading through the Yucatan Channel.

Conditions should improve across the basin by the end of the week
into the weekend. Moderate to fresh E-SE flow will prevail by Sat
night as the high pressure area that is building in behind the
cold front shifts E-NE to over the Carolinas. Seas will have
subsided to 4-7 ft across the basin by Sat night as well.

CARIBBEAN SEA...

Please see the Special Features section for information on
Hurricane Iota and on a Gale Warning in effect over the NW
Caribbean N of 20N.

Outside the influence of Hurricane Iota, isolated to scattered
moderate convection is moving across the northern islands of the
Lesser Antilles. Showers are also noted across the rest of the
Lesser Antilles. Moderate to locally fresh trade winds are noted
in the central and eastern Caribbean. Seas range 3-6 ft outside
the influence of Iota.

A new area of low pressure could form in a couple of days over the
central or southwestern Caribbean Sea. Environmental conditions
are forecast to be conducive for some development, and a tropical
depression could form by the end of the week while the system
moves slowly westward or west-southwestward across the
southwestern Caribbean Sea. Otherwise, moderate to locally fresh
trades will prevail SE of the front in the NW Caribbean through
the end of the week into the weekend. Conditions in the NW
Caribbean will greatly improve this weekend as the front washes
out.

ATLANTIC OCEAN...

See the Special Features section for details on a Gale Warning in
effect over the SW N Atlantic.

SE of the cold front discussed with the Gale Warning, another cold
front is noted, this one in the central Atlantic from 32N32W to
28N49W then becomes stationary to 29N56W. No significant
convection is associated with this front, with scattered showers
possible within 45-75 nm either side of the front. Moderate to
fresh NE winds are noted N of the front along with building seas
of 8 ft in northerly swell. Two troughs are analyzed in the
central Atlantic. The western trough is from 27N59W to 20N66W, and
the eastern trough is from 24N33W to 17N40W. Showers are possible
within 60 nm of these troughs. Moderate to fresh trades are noted
across the waters E of 60W with seas of 5-8 ft in mixed swell.

Other than the front and associated Gale Warning in the SW N
Atlantic, no other significant features are expected across the
basin through the next several days.

$$
Lewitsky
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