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Atlantic Tropical Weather Discussion

AXNT20 KNHC 181802

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
202 PM EDT Mon Jun 18 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.


A tropical wave came off the coast of Africa last night. It axis
extends from 05N19W to 13N18W, moving W at 10 kt. The wave is in 
a low or favorable deep layer wind shear environment. However, 
the GOES-16 Dust RGB and Split window imagery show the wave is 
being affected by dry air and dust, especially in the northern 
wave environment. No deep convection is associated with the wave. 
Isolated showers are from 05N-13N between 13W-22W.

A tropical wave is in the central Atlc with axis extending from 
03N31W to 12N29W, moving W at 20 kt. Similar to the wave in the E
Atlc, this wave is in a low or favorable deep layer wind shear 
environment. However, is being affected by dry air and dust, 
especially in the northern wave environment. No deep convection is
associated with the wave at the time.

A tropical wave is over the central Atlc with axis extending from
04N48W to 14N45W, moving W at 15-20 kt. GOES-16 RGB imagery show
dry air and dust intrusion in the wave environment, which along
with strong deep layer wind shear inhibit deep convection at the
time. Shallow moisture and middle to upper level diffluence
support isolated showers from 07N-12N between 45W-50W.

A tropical wave is within 120 nm SE of the Windward Islands with 
axis extending from 06N60W to 14N58W, moving W at 15 kt. This 
wave is within a very moist environment and under middle to upper 
level diffluent flow, which is supporting scattered moderate 
convection from 07N to 16N between 57W and 63W.

A tropical wave is in the central Caribbean with axis extending
from 09N76W to 19N74W, moving W at 10 kt. The wave is in a strong
or unfavorable deep layer wind shear environment and GOES-16
middle and lower level water vapor imagery show very dry air in 
the central Caribbean. These two factor are hindering the 
development of deep convection at the time.


The monsoon trough extends from the coast of Africa near 09N13W 
to 05N20W to 04N28W. The ITCZ begins near 03N34W and continues to
05N46W. In addition to the convection associated with the 
tropical waves, scattered showers are from 01N to 07N between 20W
and 29W and from 05N to 11N between 50W and 56W.



Scattered to numerous heavy showers and thunderstorms are over 
the NW Gulf of Mexico associated with a middle to upper level low 
interacting with a surface trough located along the Texas coast. 
Development of this system is not anticipated. However, heavy 
rainfall and flash flooding across portions of southern and 
southeastern Texas are likely to continue during the next few 
days. The pressure gradient between this area of low pressure and
a ridge anchored in the SE CONUS extending into the NE Gulf
support fresh to strong SE to S winds N of 22N between 91W and 
95W. The ridge is forecast to weaken by Tue evening and the winds
will diminish to less than 20 kt. Light to fresh return flow will
dominate across the basin thereafter through Wed night, with the 
strongest winds being in the western half of the basin.


Strong trades across the S central Caribbean will gradually 
decrease in areal coverage through Tue morning as high pressure in
the SW N Atlc shift east. Fresh to strong winds will pulse at
night in the Gulf of Honduras through early Wed morning.
Otherwise, a tropical wave moves across the central Caribbean
between Jamaica and Haiti, however no convection is associated
with it. See the tropical waves section for further information on
this wave. A new tropical wave currently within 120 nm SE of the
Windward Islands is forecast to enter the E Caribbean tonight
along with showers. The wave is forecast to move S of Puerto Rico
Tue morning and into the central Caribbean on Wed.


Weak surface ridging extends from the NW Atlc SSW to just N of the
Bahamas into the SE CONUS and support light to gentle winds along
with fair weather. Lingering moisture associated with the passage
of a cold front support isolated showers across the northern and
central Bahamas as well as the Florida Straits and the SE Florida
seaboard. To the east, a middle to upper level trough continue to
support a frontal system analyzed as a stationary front from a
1018 mb low near 29N57W SW to 26N73W. Satellite enhanced imagery
along with lighting density data show scattered showers and tstms
within 135 nm ahead of the front. Latest scatterometer data show
fresh winds nearby the low center. Otherwise, the remainder Atlc
continue under the influence of the Azores subtropical ridge being
anchored by a 1030 mb high NE of the Azores Islands. The front is
forecast to weaken and dissipate by Tue night. Surface ridging
will dominate thereafter.

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