photo #1301399

WTNT43 KNHC 172034TCDAT3Potential Tropical Cyclone Three Discussion Number 1NWS National Hurricane Center Miami FL AL032021400 PM CDT Thu Jun 17 2021Visible satellite images show that the cloud pattern associated withthe broad area of low pressure located over the southwestern Gulf ofMexico is gradually becoming better organized. Deep convection isbeginning to form a broad curved band over the eastern portion ofthe system, similar to what one might see in a developingsubtropical cyclone. Although the upper-level winds are notparticularly favorable for development, with lots of westerly shearover the area, the global models do suggest tropical/subtropicalcyclogenesis within the next 12 hours or so. Given the proximity ofthe disturbance to land, which requires tropical storm warnings atthis time, advisories are being initiated on this system as apotential tropical cyclone.Earlier scatterometer data suggested that the circulation was stillrather broad. An Air Force Hurricane Hunter plane is currentlyinvestigating the system and has not yet found a well-definedcenter. Maximum winds based on surface observations and thescatterometer pass are near 25 kt. Numerical intensity guidance donot indicate a great deal of strengthening before the systemreaches the coastline, and the official forecast is at the high endof the guidance.Since the center is not that well-defined at this time, the initialmotion estimate, 360/8 is quite uncertain. The system is expectedto move northward into a weakness in the subtropical ridge for thenext day or so and then, after landfall along the central GulfCoast, turn toward the northeast on the northwest side of amid-level anticyclone near Florida. The official track forecast isclosest to the GFS and ECMWF predictions. It should be noted,however, that these models suggest some reformation of the centernear the Louisiana coast rather than just motion from the southwestGulf to the expected coastal landfall point.Given the current and anticipated structure of this system, usersshould not focus on the exact track of the center, as rainfall andwind hazards are likely to extend well east of the center and arrivewell in advance of landfall.Key Messages:1. The system is expected to produce heavy rainfall and considerableflash, urban, and small stream flooding beginning Friday andcontinuing through the weekend along the central Gulf coast andspreading northeastward into the Southern Appalachians.2. Tropical storm conditions are expected to begin Friday in areasnear and well to the east of the center along portions of thecentral Gulf Coast from Intracoastal City, Louisiana, to theAlabama/Florida border, including New Orleans.FORECAST POSITIONS AND MAX WINDSINIT 17/2100Z 22.9N 92.4W 25 KT 30 MPH...POTENTIAL TROP CYCLONE12H 18/0600Z 24.5N 92.5W 25 KT 30 MPH...TROPICAL CYCLONE24H 18/1800Z 26.5N 92.5W 35 KT 40 MPH36H 19/0600Z 29.0N 92.0W 40 KT 45 MPH48H 19/1800Z 31.5N 89.5W 30 KT 35 MPH...INLAND60H 20/0600Z 34.0N 87.0W 25 KT 30 MPH...INLAND72H 20/1800Z 35.0N 84.0W 20 KT 25 MPH...INLAND96H 21/1800Z...DISSIPATED$$Forecaster Pasch/BrennanWTNT83 KNHC 172044TCVAT3THREE WATCH/WARNING ADVISORY NUMBER 1NWS NATIONAL HURRICANE CENTER MIAMI FL AL032021444 PM EDT THU JUN 17 2021.POTENTIAL TROPICAL CYCLONE THREECAUTION...THIS PRODUCT ONLY APPROXIMATELY CONVEYS THE EXTENT OFTROPICAL CYCLONE WIND AND SURGE WATCHES AND WARNINGS. PLEASE SEETHE LATEST PUBLIC ADVISORY FROM THE NATIONAL HURRICANE CENTER FORTHE PRECISE LATERAL EXTENT OF WIND WATCHES AND WARNINGS ALONG THECOAST...AS WELL AS THE APPROXIMATE LATERAL EXTENT OF SURGE WATCHESAND WARNINGS. THE PRECISE EXTENT OF SURGE WATCHES AND WARNINGSCAN BE FOUND IN THE NWS NATIONAL DIGITAL FORECAST DATABASE HAZARDGRIDS.ALZ263>266-LAZ049-050-052>054-056>061-063>070-072-075>078-MSZ080>082-180445-/O.NEW.KNHC.TR.W.1003.210617T2044Z-000000T0000Z/344 PM CDT THU JUN 17 2021$$ATTN...WFO...LCH...LIX...MOB...Potential Tropical Cyclone 03L 2021Last Modified: 2021-06-17 21:00 UTCPotential 03L 202103L 2021The system is expected to produce heavy rainfall and considerable flash, urban, and small stream flooding beginning Friday and continuing through the weekend along the central Gulf coast and spreading northeastward into the Southern Appalachians.Tropical storm conditions are expected to begin Friday in areas near and well to the east of the center along portions of the central Gulf Coast from Intracoastal City, Louisiana, to the Alabama/Florida border, including New Orleans.Visible satellite images show that the cloud pattern associated with the broad area of low pressure located over the southwestern Gulf of Mexico is gradually becoming better organized. Deep convection is beginning to form a broad curved band over the eastern portion of the system, similar to what one might see in a developing subtropical cyclone. Although the upper-level winds are not particularly favorable for development, with lots of westerly shear over the area, the global models do suggest tropical/subtropical cyclogenesis within the next 12 hours or so. Given the proximity of the disturbance to land, which requires tropical storm warnings at this time, advisories are being initiated on this system as a potential tropical cyclone.Earlier scatterometer data suggested that the circulation was still rather broad. An Air Force Hurricane Hunter plane is currently investigating the system and has not yet found a well-defined center. Maximum winds based on surface observations and the scatterometer pass are near 30 mph (25 knots). Numerical intensity guidance do not indicate a great deal of strengthening before the system reaches the coastline, and the official forecast is at the high end of the guidance.Since the center is not that well-defined at this time, the initial motion estimate, 360/8 is quite uncertain. The system is expected to move northward into a weakness in the subtropical ridge for the next day or so and then, after landfall along the central Gulf Coast, turn toward the northeast on the northwest side of a mid-level anticyclone near Florida. The official track forecast is closest to the GFS and ECMWF predictions. It should be noted, however, that these models suggest some reformation of the center near the Louisiana coast rather than just motion from the southwest Gulf to the expected coastal landfall point.Given the current and anticipated structure of this system, users should not focus on the exact track of the center, as rainfall and wind hazards are likely to extend well east of the center and arrive well in advance of landfall.Forecaster Pasch/Brennan. Information provided by the National Hurricane Center (NHC).