000 AXNT20 KNHC 030505 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 105 AM EDT Tue Jul 3 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 0000 UTC surface analysis and satellite imagery through 0515 UTC. ...TROPICAL WAVES... A tropical wave has an axis extending from 17N31W to 03N32W and is moving W at around 10 kt. The wave coincides with a surge of moisture as noted in the TPW product. African dust surrounds the wave. A patch of low level moisture is noted is association with the wave N of 10N while scattered moderate convection is observed where the wave meets the monsoon trough from 03N to 08N between 27W and 32W. A tropical wave extends from 19N51W to 05N52W. This feature is moving W at around 10 kt. The cloud field associated with this wave shows an inverted-V signature. This wave shows up well in the TPW animation where a high amplitude N bulge of moisture is observed. At this time, the wave is surrounded by Saharan dust which is limiting convection in the vicinity of this wave. Only a small cluster of moderate convection is noted along the wave's axis near 12N. Moisture associated with this wave will reach the Windward Islands early this afternoon. A tropical wave is moving across the central Caribbean. Its axis extends from the Windward Passage near 19N74W to the coast of Colombia 10N76W, moving westward at around 20 knots. The wave is well depicted in the moisture product. Clusters of moderate to strong convection are at the base of this wave over Colombia. the GFS model indicates abundant moisture in association with this wave over the SW Caribbean today, spreading over Nicaragua and Honduras this afternoon and tonight. ...MONSOON TROUGH/ITCZ... The monsoon trough enters the Atlantic Ocean through the coastal section of Senegal, then continues SW to near 10N23W to 05N38W. The ITCZ extends from 05N38W to 04N45W to 06N52W. Aside from the convection associated with the tropical waves, scattered moderate convection is from 04N-08N between 36W-42W, and from 07N-10N between 44W-49W. ...DISCUSSION... GULF OF MEXICO... As of 0300 UTC, a trough extends from a weak surface low of 1015 mb located near 30N88W to 24N90W. Scattered to numerous showers and thunderstorms can be expected near this system as it continues to interact with tropical moisture. The low is forecast to slowly move W toward NE Texas through Wed. The remainder of the Gulf remains under the influence of a weak ridge extending W from the Atlantic. A 1017 mb high pressure center located near 26N91W is within the ridge. This system is producing mainly light to gentle anticyclonic flow and seas of 1-3 ft across much of the Gulf waters. This pattern will change little through mid-week. A surface trough will emerge off the Yucatan Peninsula each evening through Thu, enhancing nocturnal winds over the SW Gulf through Sat. CARIBBEAN SEA... A tropical wave is moving across the central Caribbean. Please see the Tropical Waves section for details. A recent ASCAT pass provides observations of fresh trades over the south-central Caribbean with moderate to locally fresh winds elsewhere S of 18N E of 80W. Light to gentle winds are noted over the NW Caribbean. Winds are forecast to increase across the central Caribbean beginning tonight. Marine guidance suggests winds in the 25-30 kt range over the south-central Caribbean, with building seas to 10-12 ft by early Wed morning. Near gale force NE winds are possible near the coast of Colombia Wed night and Thu night. Convection continues to intermittently flare up over the SW Caribbean mainly in the vicinity of the monsoon trough, which is just north of Panama along 09N-10N. This pattern will remain in place for the next several days. Lightning density indicates frequent lightning with much of the observed convection. ATLANTIC OCEAN... Two tropical waves are moving across the waters between the coast of West Africa and the Lesser Antilles. Please refer to the Tropical Waves section above for details. An upper-level low is spinning NE of the Bahamas near 29N71W. A surface low and associated trough, reflection of this system aloft, is analyzed on the 0000 UTC surface map. The trough extends from 31N66W to a 1014 mb weak low pressure located near 27N70W to 24N78W. A recent scatterometer pass clearly shows the wind shift related to the trough axis particularly between 65W-70W. This system has weakened the Atlantic ridge over the western Atlantic. The low will move SW towards the Bahamas. The ridge will rebuild and strengthen Wed through Sat night as the low weakens into a trough and tracks across the NW Bahamas and over Florida by Wed. An increase in moisture is likely along and behind the trough, increasing the likelihood of showers and tstms over the Florida Peninsula. As the ridge builds westward, winds N of Hispaniola will pulse to strong speeds each day during the late afternoon and evening hours beginning on Wed. Farther E, another trough is analyzed from 33N49W to 28N51W. This trough is also associated with an upper-level low that is helping to induce scattered showers with embedded tstms from 30N-33N between 46W-53W. Surface high pressure of 1033 mb located NW of the Azores extends a ridge across the remainder of the central and eastern Atlantic forecast waters. Moderate to fresh trade winds are noted along the southern periphery of the ridge. GOES-16 RGB Geocolor imagery continues to show an extensive area of African dust that primarily extends from the west coast of Africa to the northeastern Caribbean. The Saharan Layer (SAL) from CIMSS also confirms the presence of this African dust outbreak. For additional information please visit http://www.hurricanes.gov/marine $$ GR