881 AXNT20 KNHC 121201 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 801 AM EDT Thu Jul 12 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 1115 UTC. ...SPECIAL FEATURES... Chris was downgraded to tropical storm at 12/0900 UTC, and It is forecast to become a post-tropical cyclone later today. At this time, Chris is located near 42.1N 60.1W, or about 215 nm...395 km SE of Halifax, Nova Scotia. Chris is moving toward the northeast, or 45 degrees, at 30 knots. On the forecast track, the center of Chris will pass over or near extreme southeastern Newfoundland later today or tonight. The estimated minimum central pressure is 985 mb. The maximum sustained wind speed is 60 kt with gusts to 75 kt. Additional weakening is anticipated during the next few days. Numerous moderate convection is observed within about 180 nm NE semicircle of center, and in a band within 245 nm SE quadrant. Please read the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC for more details. ...Gale in the Caribbean... A tight pressure gradient will develop across the southern Caribbean inducing gale-force winds from 11N-13N between 70W- 76W in 24 hours. These conditions will continue through the next 12 hours. Fresh to strong winds will prevail across the area after this. Refer to the High Seas Forecast product, under the AWIPS/WMO headers HSFAT2/FZNT02 KNHC, for more details. ...TROPICAL WAVES... A tropical wave extends its axis along 31W from 05N-19N. The wave is moving west at 20-25 kt. Scattered showers are noted where the wave meets the Monsoon Trough near 09N31W. This wave coincides with a good surge of moisture based on the TPW product, and model diagnostic guidance also confirms its presence. A tropical wave has its axis along 45W from 07N-20N, moving west at 15-20 kt. Saharan dust follows this wave inhibiting convection at this time. Satellite imagery indicates some inverted-V pattern in the cloud field associated with this wave. A low amplitude tropical wave extends its axis along 64W from 08N-15N, moving west 10-15 kt. Saharan dust surrounds the wave inhibiting convection. GFS computer model suggests an increase in moisture in association with this wave reaching the central Caribbean by Friday. Another tropical wave is moving across the western Caribbean. Its axis along 85W from 10N-21N, moving west at 10-15 knots. Saharan Air Layer from CIMSS shows African dust behind the wave's axis covering the basin all the way to the Lesser Antilles. The wave is helping to induce some convection just S of the Yucatan Channel, and in the Gulf of Honduras. ...MONSOON TROUGH/ITCZ... The monsoon trough passes through the coastal sections of The Gambia near 13N17W to 09N40W. The ITCZ extends from 10N46W to 08N54W to 10N62W. Aside from the showers related to the tropical wave along 27W, no significant convection is observed at this time. ...DISCUSSION... GULF OF MEXICO... A surface ridge dominates the Gulf waters anchored by a 1017 mb high centered over the north-central Gulf near 28N91W. Scattered showers and tstms are noted over the NE Gulf waters N of 26N E of 90W enhanced by an upper-level low. High pressure is forecast to prevail across the northern Gulf waters through Mon. A surface trough will move westward off the Yucatan Peninsula each evening through Mon and slightly enhance nocturnal winds and waves over the SW Gulf. A Tropical wave in the western Caribbean will move W across the Yucatan Peninsula today and across the SW Gulf tonight through Fri. Large area of African dust behind this wave will invade the southern Gulf next few days. CARIBBEAN SEA... Two tropical waves are moving across the basin. Refer to the Tropical Waves section above for details. A gale warning is in effect for the south-central Caribbean. Refer to the Special Features section above for details. The Atlantic high pressure will build across the region behind the tropical wave with axis along 85W to freshen tradewinds across the central Caribbean waters. Winds will pulse to strong to near gale force each night off Colombia beginning tonight through at least Mon night. Large area of Saharan dust behind the western Caribbean tropical wave will dominate next few days. Typical July winds and seas expected across the region next several days. ATLANTIC OCEAN... As of 0900 UTC, T.S. Chris is centered north of the forecast area near 42.1N 60.1W. Even though Chris is moving away from the United States, swells generated by the storm will affect portions of the coast from North Carolina northward to New England during the next couple of days. Swells will spread northward along the southern coasts of Nova Scotia and Newfoundland today. These swells could cause life-threatening surf and rip current conditions. Refer to Special Features section above for more details. An area of disorganized showers and thunderstorms associated with the remnants of Beryl is located about midway between the Bahamas and Bermuda. Little or no development is expected through Friday while the system moves northeastward. However, environmental conditions could become a little more favorable over the weekend when the disturbance will be moving northward over the warm waters of the western Atlantic and interacting with a strong upper-level trough. The latest Tropical Weather Outlook gives this system a low chance of tropical cyclone formation during the next 48 hours. An area of showers and tstms is noted in the wake of a surface trough extending from 28N58W to 20N60W. Lightning density indicates frequent lightning within the observed convective activity. This trough is a reflection of an upper-level low. Surface ridge prevails across the remainder of the Atlantic forecast area, anchored by a 1036 mb high pressure centered near NW of the Azores near 42N33W. The ridge extends into the NE Caribbean. The Saharan Air Layer (SAL) from CIMSS shows a new surge of African dust over the eastern Atlantic, and behind the tropical wave along 45W. For additional information please visit http://www.hurricanes.gov/marine $$ GR