Tropical Weather Discussion
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AXNT20 KNHC 200005

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 PM EDT Wed Jul 19 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.


A tropical wave is over the far eastern Atlc with its axis
extending from near 14N20W to 05N21W, moving W at 5-10 kt within
the last 24 hours. Saharan dry air and dust is in the wave
environment according to enhanced satellite data. CIRA low to mid
level moisture imagery show patches of dry air, thus confirming
the presence of SAL. Shallow moisture, favorable to neutral wind
shear and upper level diffluence support scattered moderate
convection from 08N to 14N E of 27W.

A tropical wave is in the central Atlc associated with a 1012 mb
low near 12N46W. The wave axis extends from 21N44W to the low to
08N46W and it has been moving W at 15 kt within the last 24 hours.
Intrusion of Saharan dry air and dust continue to affect the wave
environment, which is limiting the convection to scattered showers
from 10N to 14N between 45W and 49W.

A tropical wave is over the eastern Caribbean Sea, which denotes
the remnants of former Tropical Storm Don. The wave axis extends
from 16N67W to 09N68W. The wave is in an unfavorable wind shear
environment. However, abundant low to mid level moisture along
with divergent flow aloft support scattered showers and tstms S of
15N between 65W and 72W.

A tropical wave is in the central Caribbean with axis extending
from 18N72W to 10N73W, moving W at 20 kt within the last 24 hours.
CIRA LPW imagery depict abundant moisture associated with this
wave that is in an unfavorable wind shear environment. With lack
of lifting support from aloft, showers and tstms are only
confined to northern Haiti.


The monsoon trough axis extends from 12N16W to 09N30W to 11N47W.
The ITCZ then extends from 11N47W to 10N61W. Aside from the
convection associated with the tropical waves, scattered moderate
convection is from 05N to 12N between 25W and 37W.



Surface to middle level ridging is across the basin. At the
surface, a 1019 mb high near 27N92W anchors the ridge that
continues to provide gentle to light variable wind flow. An upper
level trough along the SE CONUS supports a surface trough across
Florida, which is generating heavy showers and tstms mainly in the
northern and central peninsula. Numerous heavy showers and
isolated tstms are over southern Mexico and the Yucatan Peninsula
supported by a surface trough and upper level low centered just N
of the Yucatan Peninsula. Otherwise, isolated showers are noted
in the SW basin and over Louisiana coastal waters. No major
changes are expected in this pattern for the next two days.


The main features in the basin are the remnants of former tropical
storm Don, currently analyzed as an open tropical wave, and a
tropical wave in the central basin. Both features are discussed in
the tropical waves section. See above for details. A potential
tropical wave along with the EPAC extension of the monsoon trough
support scattered heavy showers and tstms in the SW Caribbean S of
13N. Similar shower activity is along the S coast of Cuba being
supported by shallow moisture and middle level diffluent flow.
Otherwise, fresh to strong winds prevail across the central basin
generally between 66W and 80W. Scattered moderate isolated strong
convection over the SW Caribbean will remain quite active through


A fast moving tropical wave is moving across the western portion
of the island. Scattered heavy showers and thunderstorms are
noted over northern Haiti. These showers are expected to cease by
Thursday morning as the wave races westward tonight.


As climatology dictates for this time of year, tropical waves
are moving through the tropical Atlantic waters. See above for
discussions on these features. A mid/upper level trough over the
southeastern United States in combination with ample moisture and
instability is resulting in scattered showers and thunderstorms
over the SW Atlc N of 26N W of 72W. Otherwise, the remainder basin
is under the influence of the Azores high anchored by a 1029 mb
high N of the area.

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