Tropical Weather Discussion

axnt20 knhc 191204

Tropical weather discussion
NWS National Hurricane Center Miami FL
804 am EDT Tue Jun 19 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 0600 UTC surface analysis and satellite imagery through 
1130 UTC.

...Special feature...

Surface observations and NOAA Doppler weather radar data indicate
that a surface trough associated with a low- and mid-level low 
pressure system has moved inland over the Texas coastal plain. 
Although this system is producing a widespread area of cloudiness 
and disorganized showers and thunderstorms, interaction with land 
and proximity to dry air in the mid-levels of the atmosphere 
should prevent a tropical cyclone forming. However, this 
disturbance is likely to produce additional heavy rainfall and 
flash flooding across portions of southern and southeastern Texas 
during the next few days. As much as 7 to 10 inches of rainfall is
possible along the Texas coastal Bend during the next 1 to 2 
days. For more details on this disturbance and the threat for 
heavy rainfall, please see products issued by your local weather 
office and high seas forecasts issued by the National Weather 

...Tropical waves... 

A tropical wave axis extends from 05n22w to 14n22w, moving W from 
Africa around 20 kt in a low vertical shear environment. Composite
tpw satellite imagery shows this system is embedded in deep layer
moisture. Despite the favorable environment, only moderate
convection is observed from 04n to 07n between 22w and 25w.

A tropical wave axis in the central Atlc extends from 04n35w to 
12n34w, moving W around 15 kt in a high shear environment due to
an upper-level trough over the Atlc near 40w. It is being 
affected by dry air and dust, and no deep convection is associated
with this wave.

A tropical wave axis in the west-central Atlc extends from 
05n52w to 14n49w, moving W around 10 kt. GOES-16 rgb imagery 
shows dry air and dust intrusion in the wave environment, which 
along with strong wind shear is inhibiting deep convection.

A tropical wave axis entering the eastern Caribbean extends from 
05n65w to 16n64w, moving W at 15 to 20 kt. This wave is within a 
very moist environment and upper level diffluent flow, supporting 
scattered moderate and isolated strong convection over the Leeward
Islands from 13n to 17n between 61w and 65w.

A tropical wave axis over the western Caribbean extends from 
10n80w to 20n80w, moving W at 10 to 15 kt in a strong wind shear 
environment. GOES-16 middle and lower level water vapor imagery 
show very dry air in the region. These two factors are hindering 
the development of deep convection at the time.

...Monsoon trough/ITCZ...

the monsoon trough extends from Sierra Leone on the coast of 
Africa near 08n13w to 06n22w. The ITCZ continues from 06n23w to
04n38w to 05n47w to the coast of French Guyana near 05n52w. 
Scattered moderate and isolated strong convection is present from
04n to 06n between 09w and 18w and from 03n to 06n between 26w 
and 35w.


Gulf of Mexico...

Scattered to numerous showers and thunderstorms are over the NW 
Gulf of Mexico, associated with an upper level low interacting 
with a surface trough near the Texas coast. See the special 
features section for more details on this system. The pressure 
gradient between the area of low pressure and a ridge across the 
se conus extending into the NE Gulf supports fresh to strong se to
S winds N of 22n between 91w and 95w. The ridge will weaken by 
Tue evening, winds diminishing to below 20 kt. Gentle to moderate 
return flow will dominate the basin thereafter through Wed night, 
with strongest winds being west of 90w.

Caribbean Sea...

Strong trades across the S central Caribbean will gradually 
decrease in areal coverage this morning as high pressure in the 
SW N Atlc shifts east. Fresh to strong winds will pulse at night 
in the Gulf of Honduras through early Wed morning. Otherwise, a 
tropical wave passing west of the Windward Islands will move 
across the E Caribbean today along with showers. The wave will 
move S of Puerto Rico, then into the central Caribbean on Wed.

Atlantic Ocean...

A weakening stationary front extends SW from 32n54w to east of 
the Bahamas near 25n66w to 26n73w. Weak surface ridging north of 
the front supports light to gentle NE to E winds and mostly fair 
weather. Scattered moderate and isolated strong convection is seen
from 24n to 28n between 55w and 63w. A mid- level trough 
continues to support widely scattered showers within 150 nm ahead 
of the front. Latest scatterometer data shows fresh winds near the
low center. The remainder of the Atlantic is under the influence 
of the Azores subtropical ridge anchored by a 1027 mb high over 
the Azores Islands. The front will weaken today then dissipate 
tonight. Surface ridging will dominate thereafter.

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