000 AXNT20 KNHC 081737 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 0205 PM EDT Tue May 8 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 1645 UTC. ...MONSOON TROUGH/ITCZ... The monsoon trough meanders westward across Tropical western Africa and terminates along the coast of Guinea-Bissau near 12N16W. The ITCZ begins offshore of Liberia near 05N12.5W and continues to 01.5N40W to 00N45W to the coast of northern Brazil near 01N51W. Scattered moderate to strong convection is noted from 00N to 04N between 15W and coastal Brazil. ...DISCUSSION GULF OF MEXICO... A very broad mid-latitude trough continues to move slowly eastward across the eastern U.S. today, and extends SW across much of the northern half of the Gulf to 25N89W. Sinking vertical motion within the trough is aiding in producing mostly clear skies across most of the N half of the basin. To the SE, a stalled and dying frontal boundary extends from the NW Bahamas southwestward across the Florida Keys and then into the SE gulf. A 1020 mb high pressure is centered over the northwest Gulf behind the front near 26.5N95W, maintaining generally gentle to light winds and slight seas. Moderate to locally fresh NE winds are noted over the far eastern Gulf between the high pressure and the tail of the front, supporting 3 to 5 ft seas. An upper level disturbance sinking SE into central Mexico is producing high clouds across the SW Gulf, however no significant shower activity is observed. The high pressure will shift east toward the northeast Gulf through Fri, then into the Atlantic on Sat. This will maintain moderate NE to E winds and 3 to 4 ft seas across the eastern Gulf through the period. High daily temperatures over the Yucatan peninsula will set up a weak thermal trough each evening, which will move westward over the eastern Bay of Campeche overnight then dissipate by afternoon each day beginning Wed. CARIBBEAN SEA... A sharp elongated trough reaches from the Cayman Islands SSE to offshore of Colombia, while troughing also lingers SE of the old front across the NW Bahamas, extending SW across central Cuba to a dying low pressure center near 20N83W. Broad ridging over the central Atlantic is supporting moderate to fresh E to SE winds across the basin east of the trough off Colombia, where seas are running 5 to 7 ft. Generally gentle to light northerly winds are noted across the Caribbean W of the trough. Moderate to fresh trade winds are noted across the tropical north Atlantic waters west of 50W, south of the main ridge. Seas are 6 to 8 ft in decaying NE to E swell. Regional radar mosaics indicate scattered warm topped showers with isolated tstorms south of central Cuba and Jamaica to 15N occurring along and E of the trough, and to the immediate N and NW of the dying low center near 20N83W. Widely scattered passing trade wind showers are observed moving W to NW off the Atlantic into the Windward and Leeward Islands and across the NE Caribbean. Otherwise, no significant weather is noted. The trough is expected to drift westward and weaken through mid week, but will remain the focus for showers and a few thunderstorms through late today as the supporting mid/upper trough lifts northeast and dampens out. Trade wind flow will increase over the south central Caribbean by Fri night as ridging builds north of the region. Little change otherwise in the forecast. ATLANTIC OCEAN... The aforementioned old frontal boundary reaches from weak 1014 mb low pressure centered north of the area near 32N73W southwestward across the NW Bahamas then across the Florida Keys. Moderate N to NE winds prevail across the Atlantic the W of the front. Moderat to fresh SE to S winds occurring the the SW of the Atlantic ridge are producing converging moisture along and to the E of the front and a weak pre frontal trough just SE of it across the Bahamas. A mid to upper level jet entering the area from the Yucatan Peninsula to just E of the front becomes divergent eastward to 70W and is providing unstable conditions aloft to supper scattered moderate to strong convection within 200 nm SE of the front, from the central Bahamas NNE to beyond 31N. The front is meandering today and is not expected to move much through Wednesday before the ridge to the E begins to nudge the old boundary WNW by Wednesday night or Thursday. The winds to the E of the front will diminish to moderate by Wed as the low pressure lifts north. High pressure ridging extending east to west along 31N Fri through Sat night will generate gentle to moderate E to SE winds over the forecast waters, except that fresh to locally strong winds will pulse between the southeast Bahamas and the coast of Hispaniola. The Atlantic ridge is centered on a pair of high pressure centers along about 35N and between 30W and 50W. This alignment is producing moderate to fresh tradewinds across the basin to the south of 28N from the Cabo Verdes to the Caribbean, where winds begin to veer SE into the Turks and Caicos and then SSE further N, ahead of the front. Farther east, a mid/upper trough reaches from just S of the Azores to a deep layered upper cyclone near 24N39W, then extends W and SW and a very broad cyclonic circulation to 65W. Despite upper support on the east side of the mid/upper trough, no significant moisture is noted north of the ITCZ as deep layer moisture remains limited, and dry stable air continues to exit westward off of W Africa. The surface ridge will shift slowly NE through the end of the week and maintain moderate to fresh tradewinds across the Tropical Atlantic. For additional information please visit http://www.hurricanes.gov/marine $$ Stripling