000 AXNT20 KNHC 031744 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 144 PM EDT Fri Nov 3 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 1200 UTC surface analysis and satellite imagery through 1715 UTC. ..ITCZ/MONSOON TROUGH... The monsoon trough axis extends from the African coast near 10N14W to 08N19W. The Intertropical Convergence Zone extends from 08N19W to 07N28W to 09N38W where it is bisected by the trough along the position from 14N37W to 09N40W to 04N41W. It resumes to the W of the trough at 08N41W to 08N49W to near 10N55W. Scattered moderate convection is within 120 nm N of the ITCZ between 25W and 30W, within 120 nm S of the axis between 29W and 34W and within 30 nm of the monsoon trough axis between 15W and 22W. Scattered moderate moderate to isolated strong convection is observed to the S of the ITCZ within 60 nm of line from 06N13W to 04N16W, and within 30 nm of line from 03N25W to 03N30W. ...DISCUSSION... GULF OF MEXICO... Strong upper zonal flow prevails throughout the SE United States and Gulf of Mexico. A jetstream branch is across the central part of the basin is advecting broken high clouds ESE from 21N to 28N and to the E of Texas. At the surface, a 1023 mb high is analyzed over the border between western S Carolina and NE Georgia. A well entrenched ridge extends from this high center southwestward to across southern Louisiana and to the northern part of the SW Gulf. The associated pressure gradient is allowing for generally gentle to moderate NE to E winds over the basin, except in the far western section where winds are gentle to moderate, SE to S in direction. The Gulf is void of deep convection as very limited low-level moisture in combination with the subsidence aloft and the strong zonal winds are not conducive this type for this type of convection to develop. Latest satellite imagery shows small patches of low-level moisture moving quickly SW over the southeastern Gulf. Isolated showers are possible with these clouds. Little overall changes are expected with the current weather pattern over the area through Sunday. CARIBBEAN SEA... In the upper levels, a small anticyclone is centered near 16N74W, with a ridge stretching WNW to across Belize and the southern Yucatan Peninsula, and another ridge extending southeastward to far NE Venezuela. Water vapor imagery shows associated strong subsidence covering just about the entire sea, except the far western section S of 18N and W of 77W, and over the extreme southeastern portion of the sea. The dry air resulting from the subsidence is inhibiting deep convection from developing across the open waters of the basin. Only patches of low-level moisture with isolated showers and thunderstorms moving westward are seen over these waters, including the waters just SW of the Windward passage. In the western portion S of 18N and W of 77W scattered moderate isolated strong convection in clusters are observed where low- level convergence exists along with the additional factor of a surface trough that is just along the coasts of southern Honduras to that of Costa Rica. This activity should remain active into Saturday night. Low-level moisture related to a surface trough nearing the Windward Islands from the Atlantic basin is noted S of 14N and E of 63W. Isolated showers are occurring with this moisture. This moisture will gradually increase through Saturday, with the possibility of some scattered shower and thunderstorm activity moving over this part of the sea. Presently, it appears most of this activity should remain just to the E of the islands as upper level winds shear off the tops of the deeper convection. ...HISPANIOLA... Patches of low-level moisture with scattered showers are moving quickly westward just offshore the northern and southern coasts of Hispaniola. Some showers are affecting portions of these coasts. With abundant dry sinking air aloft over and near the island, the shower activity is expected to be rather shallow as it continues in a westward motion over the next couple of days. ATLANTIC OCEAN... A well-defined surface trough is analyzed over the western Atlantic from near 30N74W to a small and weak low-level swirl at 26N75W and to the SE Bahamas. A shortwave trough embedded in the westerly flow aloft has triggered off scattered moderate isolated strong convection to the NE of the trough N of 29N between 71W and 75W. The shortwave trough will shift eastward through Sunday as a longwave trough develops over the far western portion of the area. The surface trough will continue westward to near 78W to include the vicinity of the NW Bahamas on Sunday. To the E of the upper mentioned features, an upper-level low is located over the central Atlantic near 32N54W, with a sharp upper trough stretching S to 28N54W and southeastward to near 18N52W to near 13N51W. At the surface a weak trough extends from 32N52W to a dissipating low at 27N56W and to near 25N59W. Only isolated showers are along and within about 60-90 nm of the trough. A broad upper-level diffluent flow pattern is present to the E of the upper-level low and trough. Latest satellite imagery shows abundant moisture in the form of multilayer clouds with numerous showers and scattered thunderstorms to the N of 19N between 45W and 53W. The majority of this moisture along with shower and thunderstorms is advecting northward. Broken to scattered mid and high level clouds are streaming eastward from the abundant moisture area towards 20W, while at the surface and low-levels scattered to broken low clouds with isolated showers are noted. The aforementioned shower and thunderstorm activity is forecast to remain quite active during the next 24-48 hours. A surface trough is analyzed over the deep tropics along a position from 14N37W to 09N40W to 04N41W. This trough is moving westward around 15 kt. Scattered moderate convection is seen to its NW within 30 nm of line from 13N42W to 14N37W, and is being aided by upper-level divergence occurring E of the upper level trough axis that is along 28N54W to 18N52W to 13N51W. Other scattered moderate convection is southeast of the trough within 30 nm of a line from 05N32W to 05N40W. To the W of the upper trough described in above paragraph, a surface trough is analyzed from near 22N54W to 16N58W to near 09N60W. Although the upper air over this trough is very dry as noted in the latest water vapor imagery depicting abundant moderate to strong subsidence over the trough, an upper level disturbance riding southeastward in the upper NW flow is helping to produce an area of scattered moderate isolated strong convection along and within 120 nm E of this trough from 09N to 13N. The trough will move across most of the Lesser Antilles tonight into Saturday and across the eastern Caribbean Sea Saturday. The trough should bring scattered shower and thunderstorm activity to mainly the Windward Islands, and isolated showers to the rest of the Lesser Antilles through Saturday. For additional information please visit http://www.hurricanes.gov/marine $$ Aguirre