Issued at 300 AM CST Mon Jun 30 2025
000 WTPZ41 KNHC 300837 TCDEP1 Tropical Storm Flossie Discussion Number 5 NWS National Hurricane Center Miami FL EP062025 300 AM CST Mon Jun 30 2025 A 30/0357 UTC ASCAT-B pass over Flossie showed a sizable area of 30-35 kt winds in the NE quadrant, with 25-30 kt winds wrapping into portions of the SE and NW quadrants. The ASCAT data also indicates that the RMW has contracted to about 40 n mi. SSMIS and GMI microwave passes between 00-03Z were also helpful in diagnosing the position and structure of Flossie. Since the time of the above-mentioned microwave images, GOES satellite imagery indicates that Flossie has started to become better organized, and it appears that the low-level center is likely underneath the northern portion of the central convective area, which has increased in size and contains a large area of cloud tops colder than -80 degrees C. The initial intensity is set to 40 kt due to the improved organization since the time of the ASCAT pass. This estimate is also in line with the latest objective intensity estimates from the UW-CIMSS ADT, AiDT and DPRINT, which are running in the 40-45 kt range. Atmospheric and oceanic conditions are expected to remain favorable for intensification for at least another 48 h as Flossie moves through an environment of warm water, weak vertical wind shear, and a moist mid-level troposphere. Rapid intensification remains a distinct possibility over the next day or two. The NHC forecast continues to show steady to rapid intensification. The official forecast is near the higher end of the intensity guidance envelope. Beyond 48 h, Flossie should gradually encounter a dry and stable airmass and cross over cooling waters which will lead to steady weakening. The initial motion estimate is toward the northwest, or 315/9 kt. A motion between west-northwest and northwest should continue for the next few days as Flossie moves through a break in the subtropical ridge. The NHC track forecast is mostly unchanged from the previous official forecast, and lies in between the simple and corrected consensus aids. The latest NHC forecast has necessitated the issuance of a Tropical Storm Warning for portions of the coast of Mexico, as tropical-storm-force wind speed probabilities are in the 40 to 50 percent range for portions of the area. Residents of Mexico should stay updated on the latest forecast. A shift in track to the right of the official forecast could bring more significant impacts to the coast of southwestern Mexico. KEY MESSAGES: 1. The outer bands of Tropical Storm Flossie may bring locally heavy rainfall to the Mexican states of Oaxaca, Guerrero, Michoacán, Colima, and Jalisco through mid-week. Life-threatening flooding and mudslides are possible, particularly in areas of steep terrain. 2. A tropical storm warning has been issued for a portion of southwestern Mexico, where tropical storm conditions are expected late today through Tuesday. FORECAST POSITIONS AND MAX WINDS INIT 30/0900Z 15.0N 101.8W 40 KT 45 MPH 12H 30/1800Z 15.7N 102.9W 50 KT 60 MPH 24H 01/0600Z 16.8N 104.6W 65 KT 75 MPH 36H 01/1800Z 17.7N 106.3W 80 KT 90 MPH 48H 02/0600Z 18.5N 107.7W 85 KT 100 MPH 60H 02/1800Z 19.4N 108.8W 80 KT 90 MPH 72H 03/0600Z 20.4N 109.8W 65 KT 75 MPH 96H 04/0600Z 22.7N 111.9W 45 KT 50 MPH...POST-TROPICAL 120H 05/0600Z 24.9N 114.1W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Hagen