000 AXNT20 KNHC 231801 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 201 PM EDT Sun Jul 23 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 1745 UTC. ...TROPICAL WAVES... A tropical wave is in the E Atlc with axis extending from 16N22W to 05N22W, moving W at 15 kt within the last 24 hours. The wave is in a region of favorable to neutral vertical shear, however continue to be severely affected by Saharan dry air dust. Both CIRA LPW and SSMI TPW imagery confirm the extensive presence of the dry air mainly in the northern wave environment. Shallow moisture associated with the African monsoon along with upper level diffluence support scattered showers from 04N to 10N between 20W and 31W. A tropical wave is in the central Atlc with axis extending from 19N35W to 09N36W, moving W at 5 kt within the last 24 hours. The wave is in a region of favorable vertical shear, however the prevailing intrusion of Saharan dry air dust to its environment support lack of deep convection at the time. A tropical wave is in the central Atlc with axis extending from 16N49W to 06N50W, moving W at 15-20 kt within the last 24 hours. The wave is in a region of favorable vertical shear S of 14N, however it continues being severely affected by intrusion of Saharan dry air dust to its northern environment. Middle to upper level diffluence and shallow moisture as seen in CIRA LPW support scattered to isolated showers from 10N to 13.5N between 48W and 53W. A tropical wave is in the far W Caribbean and moving across Central America. This wave has been relocalized from the Central Caribbean to the present location based on satellite and models Hovmoller data as well as on surface observations. The wave axis extends from 20N86W to 10N86W. The wave is in a region of unfavorable vertical wind shear, however shallow moisture and upper level diffluent flow within a narrow ridge over the W Caribbean support scattered showers and isolated tstms in the Gulf of Honduras S of 18N W of 84W. ...ITCZ/MONSOON TROUGH... The monsoon trough axis extends from 10N14W and continues along 08N26W to 12N38W to 10N52W. The ITCZ begins near 10N52W and continues to 10N61W. For information about convection see the tropical waves sections above. ...DISCUSSION... GULF OF MEXICO... Weak surface ridging continues to dominate across the Gulf waters with gentle to light variable winds E of 91W and moderate southerly flow elsewhere. Instability aloft prevails in the form of divergent flow generated by a broad upper level low centered near the central Gulf at 24N89W and another upper low centered over Georgia adjacent waters near 31N76W. This is supporting a weakness in the surface ridge analyzed as a trough along 30N84W to 29N90W to 29N94W, which continues to generate scattered heavy showers and tstms along S Louisiana and adjacent waters to 28N. A col of low pressure between the upper level lows continue to support similar convection in the NE Gulf N of 26N E of 86W, including portions of central and NE Florida. Latest surface and scatterometer data show fresh to near gale winds in the area of convection S of Louisiana. Otherwise, shallow moisture and middle level diffluent flow in the SW Gulf support scattered showers in the Bay of Campeche. No major changes expected during the next two to three days. CARIBBEAN SEA... An upper level low centered near the central Gulf of Mexico and a narrow upper ridge in the NW Caribbean generate diffluent flow aloft, which along with abundant low level moisture support scattered showers and tstms over southern Cuba adjacent waters to 18N. Similar shower activity is in the Gulf of Honduras due in part to a tropical wave that will be entering Belize and the Yucatan Peninsula tonight. For further details see the tropical waves section above. The northern portion of this wave still lingers in the SW N Atlc as a surface trough just in the SW periphery of the Azores ridge. This trough that extends from 24N68W to 17N69W is supporting isolated showers across the E Dominican Republic. Another surface trough is in the SE Caribbean just moving across the Windward Islands where it is supporting scattered to isolated showers. In the SW basin, the eastern extension of the E Pacific monsoon trough support numerous to scattered heavy showers and tstms within 90 nm off the coast of Costa Rica and northern Panama. The remainder basin prevails under the influence of unfavorable vertical wind shear and dry air subsidence, which is supporting fair weather. Otherwise, strong high pressure over the Atlc extending a ridge along the northern basin increase the pressure gradient enough to maintain the continuation of fresh to near gale-force winds in the south- central Caribbean. These winds are forecast to prevail the next two days. ...HISPANIOLA... The northern energy associated with a tropical wave currently moving across the NW Caribbean and northern Central America still lingers in the SW N Atlc as a surface trough just in the SW periphery of the Azores ridge. This trough that extends from 24N68W to 17N69W is supporting isolated showers across the E Dominican Republic. Model guidance indicate this shower activity will persist through tonight and then fair weather will set in through at least Monday night. ATLANTIC OCEAN... An upper level low centered over adjacent waters of Georgia and S Carolina continue to support scattered showers and tstms just N of the Bahamas W of 76W. E of the S Bahamas, a surface trough, remnant energy of a tropical wave currently moving across Central America, support scattered showers from 22N to 25N between 67W and 70W. Otherwise, the Azores high continues to cover the remainder Atlc waters providing stability. For tropical waves activity see the waves section above. No major changes expected the two to three days. For additional information please visit http://www.hurricanes.gov/marine $$ Ramos