[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 011805
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
105 PM EST Thu Mar 01 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 1200 UTC surface analysis and satellite imagery through
1745 UTC.

...SPECIAL FEATURES...

Atlantic Gale Warning: A strong cold front associated with a
large and intense low pressure system that will reach the Mid-
Atlantic coast this afternoon before it tracks southeastward
over the waters north of the area through Fri night and begins
to drift eastward on Sat will move across the northwestern
waters of the discussion area Fri through Sat, followed by
minimal gale force W to NW winds on Fri night north of about 29N
between 65W-70W and north of about 26N between 45W-75W on Sat.
These winds will be accompanied by large seas.

Far E Atlantic Gale Warning: A tight pressure gradient existing
between deep low pressure inland over far northern Portugal and
higher pressure to its S and SW, and with the added feature of a
surface trough that stretches from along the coast of the
southwest portion of Western Sahara to near 20N22W is inducing
gale force winds north of 29N and to the east of 24W. Ascat data
from last night confirmed these winds. The OUTLOOK, for the 24
hours that follow the forecast that is valid until 02/12000 UTC,
consists of: the persistence of a westerly near gale or gale in:
IRVING, MADEIRA, and AGADIR.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends through the coastal sections of
Liberia near 06N10W to 01N12W. The ITCZ continues from 01N12W,
crossing the Equator along 13W, to 04S24W, to 03S36W. Scattered
moderate isolated strong convection is within 120 nm S of the
ITCZ axis between 27W-32W. Scattered moderate convection is
within 90 nm S of the ITCZ axis between 34W-36W.

...DISCUSSION...

GULF OF MEXICO...

The cold front, that was over far eastern Texas this morning has
moved off the coast to over the NW Gulf, and is along a position
from just NE of Galveston to 27N96W and to just east of
Brownsville and inland NE Mexico. A pre-frontal trough is
analyzed from 28.5N95W to 26N96.5W. Isolated showers are along
the trough, and mainly along the southern part of the front.
Strong northerly winds will follow the front along the coast of
Mexico until Fri evening. The front will stall from western Cuba
to near Veracruz Mexico Fri night, then dissipate Sat. A ridge
will build across the northern waters in the wake of the front.
Otherwise, weak ridging across the central gulf is supporting
light to gentle winds over the eastern Gulf with 2 to 4 ft seas,
and moderate to fresh southerly flow over the western Gulf with
4 to 6 ft seas. The fresh southerly flow will diminish through
this afternoon as the front progresses across the north-central
and NW gulf waters. The ridge over the central waters will shift
east-southeastward through this evening.

CARIBBEAN SEA...

Buoy and scatterometer satellite data indicate moderate trade
winds across the region currently. This is due to weakening high
pressure north of the area, with the exception of the waters
near and along the coast of Colombia, where stronger trades of
fresh intensity are highlighted in the latest available Ascat
pass. Similar winds, NE-E in direction, are noted in the same
Ascat pass to be along and within 60 nm south of the coast of
Hispaniola. Divergence aloft related to an upper level trough
that is positioned from the northern Leeward Islands to 12.5W74W
and to just south of Panama is supporting a few trade wind
showers from the Leeward Islands to the ABC Islands. Moderate to
strong subsidence along the trough axis and to the west of the
trough is maintaining fairly dry conditions over the remainder
of the area, except for the water north of 15N between 66W-76W
and to the south of 17N between 78W-83W where patches of
scattered to broken moving westward with isolated showers are
noted. A weak inverted trough in the easterlies, resembling a
tropical wave, is approaching the Windward Islands and southern
Leeward Islands are seen in satellite imagery. The 1354 UTC
Ascat pass nicely captured the NE-SE wind shift across the
trough axis. These winds are of the gentle to moderate range.
This feature will bring scattered showers and possible isolated
thunderstorms to those islands through possible early Fri
afternoon. Scattered showers are already ahead of the trough
over the far southeastern portion of the Caribbean. This
activity will gradually spread westward through Fri. High
pressure north of the area will support moderate to locally
fresh trade winds across the basin, with strong winds pulsing at
night off Colombia through Sat. Large NE swell will impact the
tropical Atlantic waters through Sat, with an even more
significant N swell event will propagate through NE Caribbean
Passages beginning on Sun.

ATLANTIC OCEAN...

West of 60W, light to gentle winds persist across the region
associated with weak ridging along 29N. A trough, the western
extension extension of a central Atlantic stationary front,
extends from 23N60W to 25N70W and to 25N75W. Multiple cyclonic
swirls of broken to overcast low and mid-level clouds with
isolated showers are observed within 150 nm north of the trough.
Otherwise, no significant shower or thunderstorm activity is
noted. The weak ridge along 29N will shift eastward ahead of a
cold front that will move off the NE Florida coast late this
afternoon or evening. The front will reach from Bermuda to SE
Florida Fri afternoon, just ahead of a reinforcing front which
will generate strong to gale force winds north of 27N east of
75W as a large and intense low pressure system begins to move
off the Virginia coast this afternoon. The fronts will merge Sat
and stall from 22N65W to the Windward Passage by Sun before
dissipating Mon. A significant swell event and likely the
largest of this winter season will accompany this system,
affecting all waters E of Florida and the Bahamas by the end of
this week.

East of 60W, a cold front is analyzed from near 32N26W to 25N43W
to 23N50W, where it transitions to a stationary front to 60W.
Fresh northerly winds are noted north of the front. But the main
weather impact continues to be large northerly swell dominating
the entire region to the east of 60W. Altimeter data from early
this morning and this afternoon revealed seas in the range of 10-
14 ft between 35W and 60W, and in excess of 20 ft east of 35W,
mainly in the area of gales mentioned in the Special Features
section. The swell will subside to 8 ft or less through Sun,
just ahead of another significant swell event originating out of
the north central Atlantic.

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

$$
Aguirre
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