[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 042346
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 PM Tue Aug 04 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 1800 UTC surface analysis and satellite imagery through
2145 UTC.

...SPECIAL FEATURES...

Tropical Storm Isaias was located by NOAA Doppler weather radars and
surface observations near 42.7N 74.2W at 04/2100 UTC, or about
20 miles west of Albany New York City moving quickly NNE at 35
kt. The estimated minimum central pressure is 995 mb. Maximum
sustained winds are near 55 kt (65 mph) with higher gust. The
NOAA Doppler weather radars along with surface observations and
satellite imagery indicate that widespread areas of rain with
embedded squalls and thunderstorms is racing across New England
and is now between eastern New York to the western part of
Maine, with a trailing line of squalls and strong thunderstorms
reaching the coastal waters from southwestern Maine to across
Cape Cod and southward from there to over the Atlantic waters to
near 39N71W. A 20 nm wide line of scattered showers and
thunderstorms extends from 42N69W to 40N70W.

The present motion of Isaias is expected through tonight. On the
current forecast track, the center of Isaias will continue to
move farther inland over eastern New York and Vermont this
afternoon and evening, and over southern Canada tonight. Gradual
weakening is expected this evening, followed by a faster rate of
weakening tonight. Isaias is forecast to become post-tropical
tonight or early on Wed.

Please read the latest NHC Public Advisory at
https://www.nhc.noaa.gov/text/MIATCPAT4.shtml and
Forecast/Advisory at
https://www.nhc.noaa.gov/text/MIATCMAT4.shtml for more details.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis along 25W from
02N-18N, moving westward at 10-15 kt. The wave is embedded
within deep tropical moisture south of 13N as observed on
satellite imagery and in the total precipitable water (TPW)
imagery animation. Satellite imagery reveals convection that
consists of the scattered moderate to isolated strong type
intensity from 08N to 12N between 21W-24W. Scattered moderate
convection is along the wave axis within 60 nm of 10N25W and
within 30 nm of 08N25W. A mid- level cyclonic circulation is
apparent in satellite imagery to be east of the wave axis near
11N20W and may be helping to enhance convection that is behind
the wave and south of the monsoon trough.

An eastern Atlantic tropical wave has its axis along 37W from
02N-18N, moving westward at 10-15 kt. This wave is embedded
within deep tropical moisture south of 16N as noted in the
the total precipitable water (TPW) imagery animation. Scattered
showers and thunderstorms are within 120 nm east of the wave
from 06N to 09N and within 120 nm west of the wave from 06N to
07N. Isolated showers and thunderstorms are within 30 nm of a
line from 11N33W to 11N37W.

A central Atlantic tropical wave has its axis along 49W from 01N
to 17N, moving westward at 15-20 kt. Last GOES-16 visible imagery
shows what appears to be an inverted-V shape to the low-level
clouds across the wave axis. The total precipitable water (TPW)
imagery animation suggests this as well with the moisture.
Scattered showers and thunderstorms are within 60 nm either side
of the wave from 10N-13N. Isolated showers and thunderstorms are
ahead of the wave from 09N to 12N between 51W-55W.

A western Caribbean tropical wave has its axis along south of
19N to just south of Panama. It is moving westward around 15 kt.
Scattered showers and thunderstorms are near the northern part
of the wave from western Jamaica west to 81W and from 17N to 19N.
Isolated showers and thunderstorms are elsewhere west of the
wave north of 13N.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from the coast Mauritania, Africa
near 19N16W southwestward to 10N26W and to 08N35W to near 08N47W.
The ITCZ extends west of a tropical wave from 08N51W to inland
South America at 08N60W. The W African monsoon trough segment
that extends out over the far eastern Atlantic has become
energized somewhat as the tropical wave along 25W passes through
it. Aside from convection associated with the tropical waves,
scattered moderate to isolated strong convection is within 240 nm
south of the monsoon trough between the coast of Africa and 21W.
Scattered moderate convection is within 60 nm north of the ITCZ
between 51W-54W.

GULF OF MEXICO...

Relatively weak high pressure remains across the basin, anchored
by a 1016 mb high center near 25N91W as of 2100 UTC. Latest
ASCAT data depicted light to gentle anticyclonic winds across
the basin, with rather low seas in the range of 2-4 ft. Isolated
showers and thunderstorms are confined mainly to the the Bay of
Campeche and far SE Gulf waters. Scattered moderate to isolated
strong convection is increasing just inland the coast of Mexico
between 90W-95W. Isolated showers and thunderstorms are just
inland the coast of Mexico from Tuxpan to just north of Tampico.

As for the forecast, light to gentle variable wind will dominate
the basin N of 22N through most of the period as a weak surface
ridge prevails in the region. Otherwise, moderate to fresh
northeast to east winds are expected at night in the eastern
half of the Bay of Campeche and along the Yucatan peninsula
associated with the nocturnal surface trough.

CARIBBEAN SEA...

Refer to the section above for details on the tropical wave over
the western part of the basin.

Scattered moderate to strong convection is over most Honduras and
over the central and western sections of Nicaragua. Similar
activity, enhanced by the eastern Pacific monsoon trough, is over
Panama. Scattered showers and thunderstorms are seen south of
13N and west of 76W. Mostly dry and stable conditions are over
the eastern and central sections of the basin, with just quick
westward moving isolated showers noted.

A pretty light gradient is over the basin as was verified by an
afternoon ASCAT pass that depicted gentle to moderate trades
across the basin except south of 15N between 64W-75W, where
fresh to strong easterly winds are present and are expected
to change little through the rest of the week.

As for the forecast, the Bermuda High pressure north of the area
along with the eastward extension of the eastern Pacific monsoon
trough to Colombia will support fresh to strong trades in the
central basin extending to the southwestern Caribbean Wed night
and continuing through the weekend. Simultaneously, moderate to
fresh winds are expected in the Gulf of Honduras during this
period as well as in the eastern Caribbean.

ATLANTIC OCEAN

Refer to the sections above for details on Tropical Storm
Isaias and the tropical waves moving across the basin.

A 1015 mb low is near 32N50W, with a stationary front extending
to 30N57W and to northwestward to near 32N65W. Only isolated
showers are near the low and front. A surface trough extends
from near 30N65W to 26N75W. Isolated showers and isolated weak
thunderstorms are north of 28N between 65W-69W. Another trough
that trails from Tropical Storm Isaias, enters the area at 32N79W
and continues to along the coast of South Florida to near Fort
Lauderdale. Isolated showers and thunderstorms near and east of
this trough from 26N to 32N between the trough and 75W. Scattered
showers and thunderstorms are quite active over the interior of
central Florida as very deep moisture along with southwesterly
flow contributes to the development of this activity.

An eastern Atlantic trough extends along a position from near
30N39W to 20N40W. No convection is noted with the trough.
Surface ridging extends from a 1022 mb high over the far
northeastern Atlantic near 33N28W southwestward to the south of
the aforementioned stationary front.

As for the forecast, weak low pressure will develop over the NE
offshore waters tonight and shift to the north-central waters by
Fri before dissipating over the weekend. Otherwise, moderate to
locally fresh east to southeast winds are expected across the
Great Bahama Bank and north of Hispaniola through the weekend.
Strong east winds are likely north of Hispaniola at night.

$$
Aguirre
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