817 AXNT20 KNHC 021753 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 153 PM EDT Tue Oct 2 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 1715 UTC. ...SPECIAL FEATURES... Tropical Storm Leslie is centered near 30.9N 56.1W at 1500 UTC, or 450 nm E of Bermuda, moving SW at 7 kt. Estimated minimum central pressure is 989 mb. Maximum sustained winds are 55 kt with gusts to 65 kt. A recent ASCAT pass shows that the tropical storm force winds are occurring north of 28N between 54W-59W. Scattered moderate convection is within 150 nm of the center, with the strongest convection in the northwest semicircle. A slow south- southwestward or southward motion is expected through Wed. A turn to the north is forecast to occur late Wed into Thu, followed by a motion toward the north-northeast on Fri. Gradual strengthening is expected during the next day or two, and Leslie is forecast to become a hurricane tonight or on Wednesday. Public Advisories for Leslie are under the WMO header WTNT33 KNHC, and the AWIPS header MIATCPAT3. Forecast/Advisories for Leslie are under the WMO header WTNT23 KNHC, and the AWIPS header MIATCMAT3. ...TROPICAL WAVES... A far eastern Atlantic tropical wave was added to the analysis just off the coast of Africa along 16W from 03N-16N, moving westward 10-15 kt. Scattered moderate convection is occurring within 180 nm west and 210 nm east of the wave axis. The wave coincides with a maximum in total column water vapor as depicted in the GOES-16 TPW product. The wave has a 700 mb trough associated with it, as shown by model analyses. A central Atlantic tropical wave is along 48W from 03N-14N, moving westward around 15 kt. Scattered showers are near 09N-11N between 49W-52W and between 44W-46W. These showers appear to be more related to the ITCZ than the wave. A tropical wave is just east of the Lesser Antilles along 59W and extends from Guyana to 18N, moving westward at 10 kt. A well- defined 700 mb trough is shown in model analyses just east of where the wave is analyzed. The wave has a well defined 700 mb trough associated with it but lacks significant convection. A TPW animation shows a moisture maximum is associated with this tropical wave. Only a small area of isolated showers is seen east of the wave axis from 09N-12N between 55W-58W. Otherwise, no significant convection is noted. ...MONSOON TROUGH/ITCZ... The monsoon trough extends from the coast of Senegal near 12N16W to 09N23W to 09N36W. The ITCZ extends from 09N36W to 10N48W. The ITCZ resumes west of the tropical wave along 48W and continues to 09N58W. Aside from the convection mentioned in the tropical waves section above, scattered showers and isolated thunderstorms are observed within 60 nm north and 120 nm south of the ITCZ between 36W-44W. ...DISCUSSION... GULF OF MEXICO... A weak surface trough is analyzed over the northeastern Gulf along 85W from 25N-29N. The trough is producing scattered showers and thunderstorms from 28N-29N west of 84W. This trough, along with increasing moisture in the northeastern Gulf, could help to enhance showers and thunderstorms over the northeast and north- central Gulf for the remainder of this afternoon. Expect ridging to prevail over the forecast area during the next few days. A surface trough will develop each evening over the Yucatan Peninsula. The trough will move into the SW Gulf overnight, where it will dissipate each morning. Moderate to fresh winds will accompany the trough. CARIBBEAN SEA... A broad surface trough along 79W is associated with a broad area of low pressure located over the southwestern Caribbean Sea. Satellite imagery shows numerous moderate with embedded scattered strong convection east of the trough from 12N-17N and between 72W and 77W. Elsewhere east of the surface trough, scattered moderate convection is present from 11N-18N between 71W and 78W. Two small areas of scattered moderate convection are occurring just offshore northeast Honduras and also just offshore east- central Nicaragua. The persistent strong convection east of the trough is being enhanced by an area of upper-level diffluence over the same area. Some gradual development of the broad low pressure area is possible late this week and this weekend while the low drifts generally in a northward direction. A deepening mid to upper level trough oriented E-W over the northern Caribbean and Greater Antilles will help advect moisture northward as the week progresses. As a result, heavy rain is likely to spread over sections of Hispaniola and Jamaica later this week and into the weekend. Scattered showers and thunderstorms are occurring from 19N-21N between 80W and 85W. Expect the activity in this area to remain scattered and not very strong since upper-level troughing in the area is weakening. Broad mid-level ridging is over the east- central Caribbean with associated westerly upper level flow leading to generally quiet weather conditions east of 71W. Large NNE swell generated from Leslie will pass through the Atlantic passages into the Caribbean. ATLANTIC OCEAN... The three tropical waves over the tropical Atlantic between Africa and the Lesser Antilles are described in the Tropical Waves section above. Tropical Storm Leslie is described in the Special Features section above. A broad mid to upper level trough over Leslie combined with an area of upper-level diffluence to the southeast of Leslie continues to enhance convection to the southeast of Leslie. Scattered moderate convection is observed from 24N-29N between 42W-49W. A surface trough is analyzed extending from 28N54W to 20N63W. East of the trough axis, an area of scattered moderate convection is noted from 20N-24N between 51W and 56W. Elsewhere from 20N-26N, between 50W and the trough axis, scattered showers and isolated thunderstorms are present. A shear line has developed since this morning oriented east to west from 22N65W to 25N78W. Scattered showers and thunderstorms are occurring within 60 nm of the shear line. ASCAT and surface observations show NE 20-25 kt winds along and north of the shear line. The northeastern portion of the forecast area is under the influence of a ridge, anchored by a 1018 mb surface high near 26N36W. Generally quiet weather prevails north of 20N and east of 40W. For additional information please visit http://www.hurricanes.gov/marine $$ Hagen/Aguirre