Tropical Weather Discussion
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AXNT20 KNHC 210006

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
806 PM EDT Thu Apr 20 2017

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
2345 UTC.


Tropical Depression ONE became Tropical Storm Arlene at 20/2100
UTC. The center of T.S. Arlene is near 37.7N 42.0W and is moving
west-northwest, or 290 degrees at 22 knots. The estimated minimum
central pressure is 993 mb. The maximum sustained wind speeds is 40
knots with gusts to 50 knots. Numerous moderate convection is SW
of the storm center from 37N to 39N between 41W and 45W. Please
read the public advisory under the WMO header WTNT31 KNHC and
under the AWIPS header MIATCPAT1.


The Monsoon Trough extends across the western Africa coast from
07N12W to 03N19W. The Intertropical Convergence Zone continues
from 03N19W to 02N33W to the coast of Brazil near 02S43W.
Scattered moderate convection is from 03S to 10N between 20W and
31W. Isolated showers and tstms are from 0N to 05N E of 20W.



A middle to upper level low centered NW of the Yucatan Peninsula
covers the western Gulf of Mexico where water vapor imagery show
very dry air aloft, which supports in part fair weather
conditions there. However, middle to upper level ridging across
the western Caribbean allows for a diffluent wind pattern over the
SE Gulf where abundant moisture support numerous moderate
convection and isolated tstms as indicated by the GOES lighting
density product. This convection is located S of 26N E of 89W
ahead of a surface trough in the NW Caribbean that will move over
the Yucatan Peninsula tonight bringing heavy showers to the
region. The trough is forecast to become a center of low pressure
Saturday morning over SE waters and then will track over NE Gulf
waters Sunday where it will dissipate. Otherwise, surface ridging
dominates the northern Gulf waters being anchored by a 1019 mb
high near 29N84W. This is providing mainly E-SE light to moderate
flow across the basin, except in the SE Gulf where the gradient
tightens due to the approaching surface trough and supports fresh
NE winds.


The main feature in the Caribbean is a surface trough in the NW
basin from 22N82W to central Honduras. This elongated area of low
pressure is located under a broad area of middle to upper level
diffluent flow that along with abundant moisture in the region
support scattered heavy showers and isolated tstms N of 14N W of
77W. This shower activity will continue overnight as the trough
continues to move west towards the Yucatan Peninsula. Latest
scatterometer data show fresh to locally strong E-NE winds in the
vicinity of the trough. Fresh winds extends to the central
Caribbean N of 15N, including the Windward Passage. Moderate
trades dominate elsewhere. Otherwise, SW flow aloft continue to
bring moisture from S America and the EPAC to the NE Caribbean,
thus supporting cloudiness in the region with possible isolated


Broken to overcast skies continue across the Island with possible
isolated showers extending to adjacent waters. This is due to
abundant low level moisture and a middle diffluent wind pattern
west of the Island and also moisture advection by SW flow in the
upper levels. These conditions are expected to continue during the
next two days.


Tropical storm Arlene is over central Atlantic waters N of the
area. See the special features section for further details. A cold
front enters the area from 30N42W to 23N52W then dissipates to
28N75W. No convection is associated with it. Surface high pressure
dominate elsewhere. Arlene is forecast to dissipate in 24 hours.
However, gale-force winds will develop over the central Atlantic
Sat morning.

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