Tropical Weather Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000 AXNT20 KNHC 280005 TWDAT Tropical Weather Discussion NWS National Hurricane Center Miami FL 805 PM EDT Tue Jun 27 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 1800 UTC surface analysis and satellite imagery through 2315 UTC. ...TROPICAL WAVES... A tropical wave has its axis just off the Africa coast along 18W from 10N to 20N, moving westward near 10 kt. While there is moisture aloft in the form of broken high clouds, low-level moisture noted earlier with this wave has become limited north of 16N during the afternoon. Only isolated showers and weak thunderstorms are within 180 nm west and 60 nm east of the wave axis. A tropical wave has its axis along 33W/34W from 02N to 11N, moving westward at 10-15 kt. Last visible satellite imagery and Total Precipitable water (TPW) data reveals that the wave remains embedded within a very moist and unstable environment, except for over its extreme northern segment where Saharan dry air and dust is present. The latest satellite imagery shows scattered moderate to isolated strong convection ahead of the wave within 30 nm of a line from 10N33W to 08.5N35W. Small clusters of scattered moderate convection are elsewhere within 180 nm west of the wave axis from 06N to 10N. A few small clusters of scattered moderate convection are in the wake of the wave from 08N-11N. A broad and rather robust tropical wave has its axis tilted in a northeast to southwest fashion along a position from 14.5N54W to 11N58W to inland South America at 07N59W, moving westward 15-20 kt. This wave continues to be easily identifiable on visible satellite imagery as having the typical configuration of waves observed later during the season. It is detected in the model fields, and is further supported by the latest diagnostic model analysis. Scattered moderate isolated strong convection is ahead of the wave axis within 60 nm of a line from 12N57W to 11N59W, and within 45 nm of a line from 11N59W to 10N6.5W. Scattered moderate convection is within 30 nm of a line from 13N55W to 12N57W. In the wake of the wave, scattered moderate convection is within 30 nm of 11N52W. The wave is forecast to begin to enter the southeastern Caribbean Sea late tonight into early Wednesday, then move across the rest of the eastern Caribbean through Wednesday night, and the central Caribbean portion Thursday. The wave will be accompanied by scattered showers and thunderstorms with gusty winds, and followed with some area of haze. A tropical wave is moving into the western Caribbean Sea with its axis along 80W/81W south of 21N to across northern Panama, moving westward at 10-15 kt. This wave is also evident in visible satellite imagery, and continues to mark the leading surge of very deep atmospheric moisture as seen in Total Precipitable water (TPW) data and in the satellite imagery. An area of scattered moderate to isolated strong convection is east of the wave axis to 77W and from 14N to 18N. Similar activity is within 30 nm of 12N78W. Scattered showers and isolated thunderstorms are west of the wave from 11N to 15N. The wave will move across the remainder of the western Caribbean Sea through Wednesday, and inland Central America Wednesday night. A tropical wave is just west of the Yucatan Peninsula near 91W and south of 22N, and extends southward to inland southeastern Mexico, moving westward around 10 kt. The wave has contributed to the typical diurnal convection that occurs over the Yucatan peninsula. Increasing clusters of scattered strong convection are noted over much of the interior of the Yucatan peninsula as well as the northern portion of Guatemala. This activity is beginning to spread into the far eastern section of Mexico. This wave will most likely become ill-defined over the SW Gulf on Wednesday, however the southern extent of the wave is expected to continue on westward over the eastern Pacific Ocean. ...MONSOON TROUGH/ITCZ... The Monsoon Trough axis extends from the coast of Africa near 20N17W, and continues southwest to 10N25W and to 07N32W. The Intertropical Convergence Zone then extends from just to the west of the tropical wave along 33W/34W northwest to 09N44W to 09N50W and to just east of the tropical wave along the position of 14.5N54W to 11.5N58W to 07N59W. Scattered moderate isolated strong convection is within 180 nm south of the ITCZ axis between 50W-53W. Similar activity is within 30 nm of 05N48W. Scattered moderate convection is within 120 nm south of the ITCZ axis between 37W-39W, and within 30 nm of 05N42W. ...DISCUSSION... GULF OF MEXICO... A mid to upper level trough axis is over the far NW Gulf, while a surface trough is along the Texas coast. The combination of these features along with the presence of diffluent flow aloft east of the mid-upper level trough continues to support scattered showers and thunderstorms from 24N to 27N and west of 89W, and scattered showers and isolated thunderstorms north of 27N west of 88W. A stationary front is analyzed from NE Florida southwest to near Cross City, Florida and to 29N86W where it becomes diffuse from there to just east of southeastern Louisiana. Weak high pressure is analyzed over the remainder of the Gulf. The shower and thunderstorm activity over the western Gulf is forecast to remain active tonight and Wednesday, then shift ENE Wednesday night and Thursday as the mid/upper level trough slides eastward. The stationary frontal boundary is forecast to gradually become diffuse through early Wednesday, with the remnants lifting back to the north later on Wednesday and through Wednesday night. A tropical wave is over the eastern Bay of Campeche. Associated convection is described above under Tropical Waves. CARIBBEAN SEA... The main feature presently in the basin is the tropical wave discussed in the section above, and the near future arrival of another tropical wave also discussed above expected to move into the southeastern Caribbean late tonight into early Wednesday, and move across the central Caribbean Thursday. Otherwise, a pressure gradient is analyzed throughout the basin. The southern extension of a central Atlantic mid to upper level trough passes from east to west just to the north of eastern Cuba and Hispaniola, and is helping to produce scattered showers and isolated thunderstorms over the waters between eastern Cuba and Jamaica, and over the Windward Passage. Some of the moisture with this activity is related to the tropical wave along 80W/81W, and is also moisture that is being advected towards Hispaniola by upper level westerly winds as mentioned below. The gradient is forecast to tighten over portions of the far south-central Caribbean beginning tonight and continuing through Thursday night inducing strong to near gale force east winds there, with the near gale force winds expected across and near Gulf of Venezuela. Scattered low clouds with possible isolated showers are present over the eastern half of the sea, with the exception of the far southeast sector where mid and high level clouds are increasing from the east in advance of the tropical wave that is approaching the Caribbean. In addition, scattered showers and thunderstorms, some with gusty winds, that are preceding the aforementioned tropical wave are observed just to the east and southeast of the Windward Islands. This activity will move across these islands and the southeastern Caribbean tonight into Wednesday. ...HISPANIOLA... Upper-level westerly winds continue to usher deep-level moisture over the island and surrounding waters this evening. This is contributing to the shower and thunderstorm activity that developed this afternoon to bring about a further increase to this activity. Little change is expected in the present weather pattern through Wednesday, then a gradual decrease in moisture through Thursday night as a strong tropical wave passes to the south of the island. ATLANTIC OCEAN... Broad anticyclonic aloft covers the Atlantic west of about 65W. A broad mid to upper trough extends southwestward from along the eastern seaboard to the far northwest portion of the basin. It supports a stationary front extends through 32N79W to just south of Saint Augustine, Florida as of 21Z. Scattered showers and thunderstorms are noted over much of the northwest portion north of the Bahamas and west of about 74W. This activity will continue through much of Wednesday and Wednesday evening as the surface boundary weakens, and the mid to upper trough slides eastward while it broadens out further. Surface high pressure is analyzed north of 18N between 20W and 70W, and weakens to the west of 70W. A large and well-defined mid to upper level cyclonic circulation is located over the central Atlantic near 28N56W and is nearly stationary, with an associated trough stretching from it southwest to 22N64W to 21N72W and to across the NW Caribbean Sea. The circulation covers the area north of 23N and between 49W and 62W. It is forecast to drift northward and gradually weaken to a trough through Wednesday night. Over the far eastern Atlantic, another mid to upper level cyclonic circulation is centered near 29N30W. It is moving westward. Only isolated showers and possible weak isolated thunderstorms are within 180 nm in the southeast quadrant of the circulation center. A trough extends from the circulation south-southwest to near 11N39W. For additional information please visit $$ Aguirre is the U.S. government's official web portal to all federal, state and local government web resources and services.