[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 032334
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 PM Mon Aug 03 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
2315 UTC.

...SPECIAL FEATURES...

Tropical Storm Isaias is centered near 32.0N 79.4W at 03/2100
UTC, or about 50 nm south-southeast of Charleston, South Carolina
and about 100 nm south-southwest of Myrtle Beach, South Carolina
moving NNE or 15 degrees at 14 kt. The estimated minimum central
pressure is 993 mb. Maximum sustained winds are 60 kt with gusts
to 75 kt. The NOAA Doppler weather radars from Charleston,
Wilmington, and Jacksonville depict a ragged eye-like feature
with the cyclone and the most recent GOES-16 visible imagery
shows what appears to be over-shooting cloud tops on the east
side of the apparent eye feature. The satellite imagery also
shows scattered moderate to isolated strong convection in a
pretty symmetrical pattern within 120 nm of the center in the NW
quadrant. Scattered moderate convection in banding formation is
within 30 nm of a line from 29N78W to 31N77W. Similar convection
well away from the center is within 30 nm of a line that extends
from southeastern Florida near 26N81W northeastward to 27N79W
and to 29N78W. Isolated showers and thunderstorms are elsewhere
north of 26N and west of 76W. Maximum wave heights being
generated by Isaias are up to 28 ft.

A gradual increase in the forward speed of the cyclone is
expected through tonight followed by a further increase in the
forward speed on Tue. On the forecast track, the center of Isaias
will approach the coasts of northeastern South Carolina and
southern North Carolina within the hurricane warning area this
evening. The center will then move inland across eastern North
Carolina early Tue morning, move along the coast of the mid-
Atlantic states on Tue, and continue across the northeastern
United States Tue night.

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.

A surface trough extends along a position from near 29N65W to
23N65W. GOES-16 satellite imagery shows disorganized scattered
moderate convection from 24N to 27N between 64W-66W and from
26N to 28N between 66W-68W. The trough is underneath the
southwestern periphery of an upper-level anticyclone centered
near 31N62W. Strong southeast upper-level winds are currently
over the trough. However, marginal environmental conditions could
allow for some slow development of this system during the next
few days, with a tropical depression possibly forming later this
week. This system is forecast to move northwestward through Tue,
and then stall several hundred miles southwest of Bermuda by the
middle to latter part of the week. It has a medium chance of
becoming a tropical cyclone during the next 48 hours. Please
refer to the latest NHC Tropical Weather Outlook at
www.hurricanes.gov for more details.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis along 19W from
02N to 19N, moving westward near 15 kt. The majority of this
wave is embedded with deep tropical moisture associated with the
African monsoon trough that extends into the eastern Atlantic.
Scattered moderate convection is within 300 nm west of the wave
from 05N to 10N and along and near the wave axis from 10N to 13N.

An eastern Atlantic tropical wave has its axis along 31W/32W
from 02N to 18N, moving westward at about 20 kt. This wave is
embedded within deep tropical moisture also associated with
the monsoon trough in that area of the Atlantic. The total
precipitable water (TPW) animation imagery indicates scattered
moderate convection along and within 60 nm west of the wave
axis from 05N to 09N and east of the wave axis within 60 nm of
06N30W. Scattered showers and isolated thunderstorms are noted
from 09N to 15N between 30W-35W.

A central Atlantic tropical wave has its axis along 50W from
02N-16N, moving westward at 15-20 kt. Dry and stable air is
impinging onto this wave from the northeast. Scattered moderate
convection is near where the wave axis crosses the ITCZ,
generally from 06N to 09N between 48W-52W.

A central Caribbean tropical wave has its axis along 76W south
of 19N to inland Colombia near 07N76W. It is moving westward
at about 10 kt. Scattered showers and isolated thunderstorms
are north of 14N and between Haiti and Jamaica. The northern
part of this wave may be helping to enhance scattered shower and
thunderstorm activity that is occurring along the southwestern
tip of Haiti and near the eastern tip of Cuba and inland Colombia
between 72W-76W.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from the coast of Mauritania,
Africa near 19N16W to 12N25W to 10N31W to 10N40W and to 09N48W.
The ITCZ extends from 08N51W to 09N60W. Aside from the
convection described in the Tropical Waves section above,
scattered moderate convection is within 300 nm south of the
trough axis between 24W-29W and within 180 nm south of the trough
axis between 39W-45W.

GULF OF MEXICO...

Rather weak surface high pressure remains over the basin,
anchored by a 1016 mb high center over the northwestern
Gulf near 29N94W. The associated gradient supports light to
gentle anticyclonic winds north of 23N and west of 86W. Moderate
winds are over the northeastern Gulf. Seas are ranging between
2-4 ft across the basin. Scattered showers and tstorms are seen
over the Bay of Campeche, south of 20N between 91W-96W. Isolated
showers are over the southeastern Gulf.

Mainly moderate northwest to north winds will continue across
the NE Gulf today as Tropical Storm Isaias moves north-
northeastward near the Georgia and South Carolina coasts. A weak
high pressure ridge will persist over the N Gulf this week,
maintaining gentle flow across much of the region with moderate
winds expected in the southwestern Gulf.

CARIBBEAN SEA...

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

A small upper-level anticyclone situated just north of the
Yucatan Channel near 23N86W is maintaining mid to upper-level
anticyclonic flow across over the northwestern Caribbean. An
inverted northeast to southwest aligned upper-level trough
extends from Hispaniola to inland Colombia near 10N78W. Isolated
showers and thunderstorms moving westward are seen north of 15N
and west of 78W. In the far southwestern part of the sea,
scattered showers and isolated thunderstorms are south of 11N and
west of 79W. Scattered showers and thunderstorms are just inland
the coast of Colombia between 72W-76W. Scattered showers
and thunderstorms are south of Hispaniola from 15N to just south
of its coast near 18N and between 70W-74W. This activity is
being supported by the inverted upper-level trough. Strong gusty
winds are possible with this activity as were noted by a recent
ship observation (3EBL5) near 16N73W. ASCAT data from this
afternoon depicted fresh trade winds across much of the eastern
Caribbean between 64W-73W, with gentle to moderate trade winds
elsewhere across the basin.

The Bermuda High north of the area along with the eastward
extension of the eastern Pacific monsoon trough will contribute
toward fresh to strong trade winds over the central Caribbean
from Tue through Fri. Elsewhere winds and seas are forecast to
remain rather low through the remainder of this week.

ATLANTIC OCEAN

Refer to the Special Features section above for details on
Tropical Storm Isaias and on a trough that is along 65W from
23N to 29N.

An outer band from Isaias consist of a line of scattered showers
and thunderstorms from 29N78W northeastward to 31N77W. Scattered
showers and isolated thunderstorms make up a 30 nm wide convergence
line that extends from near southeastern Florida northeastward
to the west end of Grand Bahama Island and northeastward to near
28N78W. An afternoon ASCAT pass revealed fresh to strong winds,
associated with the outer periphery of the circulation tied to
Isaias, north of 26N and west of 72W.

A north to south oriented upper-level trough extends along 70W
from the central Caribbean northward to 32N. In combination
with very moist surface to low-level flow, it is helping to
produce isolated showers and thunderstorms 23N to 29N between
68W-75W. A 1023 mb high is centered west of Bermuda near 33N68W.
A stationary front enters the discussion area from 32N50W and
extends to 31N59W. Scattered showers and thunderstorms are just
ahead of the front within 30 nm of a line from 29N56W to 29N53W
and to 31N50W. A surface trough is along a position from 29N37W
to 20N39W. No deep convection is occurring with this trough as
it is under dry air aloft and is surrounded by a stable
atmospheric environment at the surface. A surface ridge extends
from a 1026 mb high center east of the Azores near 38N22W to a
1022 mb high center near 26N52W.

As for the forecast, Tropical Storm Isaias near 32.0N 79.4W 993
mb at 5 PM EDT moving NNE at 14 kt. Maximum sustained winds 60
kt gusts 75 kt. Isaias is expected to become a hurricane, then
move inland to 34.7N 78.1W Tue morning, well north of the area.
Large seas north of 28N associated with Isaias will spread
northward across the waters west of 75W today, then gradually
subside late tonight through Tue night. A trough extending from
23N65W to 29N65W will move across the SE waters today.
Environmental conditions are conducive for development during the
next few days as this system moves northwestward near 15 kt, and
a tropical depression could form later this week.

$$
Aguirre
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