Issued at 400 AM CDT Sun Aug 27 2023
585 WTNT45 KNHC 270859 TCDAT5 Tropical Depression Ten Discussion Number 3 NWS National Hurricane Center Miami FL AL102023 400 AM CDT Sun Aug 27 2023 The small circulation of Tropical Depression Ten continues to be well-defined in Cancun radar, with the center moving across Cozumel during the past few hours. Data from a Weatherflow sensor on the island indicated that the pressure dropped to about 1001 mb, with sustained winds of about 30 kt. A small burst of convection has formed just south of the center recently, with scattered banding features in the eastern semicircle. Most of the satellite estimates are just shy of tropical storm strength, so the initial winds speed will stay 30 kt. Both Air Force Reserve and NOAA Hurricane Hunter aircraft will be in the system later this morning to get a better look at the structure and winds. The depression has turned southward tonight, moving at about 4 kt, apparently rotating around the western periphery of its larger parent circulation to the east. Little net motion is expected for about a day as steering currents remain weak. After that time, a developing trough over the Gulf of Mexico and stronger ridging over the western Atlantic is expected to lift the system toward the north and north-northeast over the eastern Gulf of Mexico. This track takes the system toward Florida, and then near the southeastern coast of the U.S. The overnight model guidance is a bit farther west and slower than the last cycle, probably due to the depression being further south than anticipated. Thus, the NHC forecast is nudged westward, and lies on the east side of the guidance envelope. These are small changes overall, and the track should be considered lower confidence until it starts moving in a more consistent manner. The NOAA G-IV aircraft should be in the area this afternoon to help smooth out the model differences along with special upper-air soundings scheduled across many areas of the southeastern United States. The very warm and deep waters of the northwestern Caribbean Sea and Gulf of Mexico should support at least gradual strengthening during the next few days, tempered by moderate shear from a flat upper- level trough. However, this trough is forecast to amplify over the western Gulf of Mexico around Tuesday, which causes the shear to decrease near the cyclone in that time frame. There's a notable risk of rapid intensification while the system moves across the record warm eastern and northeastern Gulf of Mexico, which is highlighted by the recent HAFS and HWRF guidance. The new NHC forecast is raised from the previous one, near or above the model consensus, and could be too low. I'm reluctant to make any big changes to the forecast until we get more in-situ data, but the upward overnight model trend certainly bears watching. Users are reminded to continue monitoring forecasts for any changes to the system's expected intensity as it approaches Florida. KEY MESSAGES: 1. Heavy rainfall from Tropical Depression Ten is expected across the eastern Yucatan Peninsula and western Cuba. The heavy rainfall may produce areas of flash and urban flooding, as well as landslides, across western Cuba. The depression is forecast to become a tropical storm later today, and tropical storm conditions are expected over portions of the Yucatan Peninsula and extreme western Cuba where a Tropical Storm Warning is in effect. Tropical storm conditions are possible on the Isle of Youth, where a Tropical Storm Watch is in effect. 2. The depression is forecast to strengthen during the next few days and could become a hurricane over the eastern Gulf of Mexico, bringing a potential of dangerous storm surge, heavy rainfall, and strong winds to portions of the west coast of Florida and the Florida Panhandle by the middle of this week. Heavy rainfall is also likely to spread into portions of the Southeast U.S. by mid to late week. Although it is too soon to specify the exact location and magnitude of these impacts, residents in these areas should monitor updates to the forecast of this system and ensure that they have their hurricane plan in place. FORECAST POSITIONS AND MAX WINDS INIT 27/0900Z 20.1N 86.8W 30 KT 35 MPH 12H 27/1800Z 20.1N 86.5W 40 KT 45 MPH 24H 28/0600Z 20.6N 86.3W 45 KT 50 MPH 36H 28/1800Z 21.7N 86.3W 50 KT 60 MPH 48H 29/0600Z 23.3N 86.2W 60 KT 70 MPH 60H 29/1800Z 25.7N 85.7W 75 KT 85 MPH 72H 30/0600Z 28.5N 84.7W 80 KT 90 MPH 96H 31/0600Z 33.0N 81.2W 45 KT 50 MPH...INLAND 120H 01/0600Z 35.0N 75.5W 35 KT 40 MPH...OVER WATER $$ Forecaster Blake
