Tropical Cyclone Discussion
190 WTNT44 KNHC 072049 TCDAT4 Tropical Storm Isaias Discussion Number 5 NWS National Hurricane Center Miami FL AL092026 400 PM CDT Wed Oct 07 2026 Satellite and aircraft data show that Isaias continues to strengthen. GOES-19 imagery indicates that a central dense overcast has formed, and the system has become more symmetric than this morning. The peak NOAA Hurricane Hunter aircraft 700-mb winds were 61 kt, with the pressure dropping to 994 mb. The initial intensity is set to 55 kt as a reflection of this data. Isaias is basically on track, moving east-northeast at 7 kt. There is no change to the synoptic reasoning as a deepening trough along the northwestern Gulf Coast and a strengthening Atlantic subtropical ridge should cause the system to move faster to the northeast tomorrow and northward on Friday. As long as the cyclone remains intact, it makes physical sense that the system will move on the faster and eastward side of the guidance due to the stronger shear Isaias should encounter near landfall. Thus, the new forecast is adjusted slightly to the east, closer to the AI-based and corrected-consensus models. NOAA radar data (P3-TDR) show that the system is experiencing some southwesterly shear, with tilt analyses displaying the mid-level circulation displaced 5-10 n mi to the northeast of the low-level center. This structure seems sufficient for further intensification given a continuation of similar low or moderate shear and very warm SSTs in a very humid environment. Models are fairly consistent about the shear increasing on Friday, but almost all guidance still shows a category 1 or 2 hurricane at landfall. While the regional hurricane models have generally come down on the peak intensity this cycle, it is unknown whether this is the start of a real trend, and we would prefer to see more than one guidance cycle before making any adjustments. The new forecast is close to the previous one, near the high side of the model suite. Key Messages: 1. Isaias is expected to strengthen and be a strong hurricane when it approaches the northern Gulf Coast on Friday. There is an increasing risk of life-threatening storm surge along portions of the northern Gulf Coast, and a Storm Surge Watch is in effect from The Mouth of the Mississippi River to Yankeetown, Florida. Residents in the watch area should follow advice given by local officials and evacuate if told to do so. 2. The risk of damaging hurricane-force winds is increasing over portions of the Florida Panhandle, southern Alabama, and southern Mississippi. A Hurricane Watch has been issued from Bay St. Louis, Mississippi, to Indian Pass, Florida. Residents in these areas should prepare for the possibility of long-duration power outages. 3. Isaias will bring areas of heavy rainfall to the central U.S. Gulf Coast and much of the Southeast Friday into the weekend. Flash and urban flooding, along with isolated river flooding, will be possible. 4. Isaias could bring gusty winds and areas of heavy rain to the western portion of the Yucatan Peninsula through Thursday. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 22.7N 92.9W 55 KT 65 MPH 12H 08/0600Z 23.1N 91.8W 70 KT 80 MPH 24H 08/1800Z 24.1N 90.1W 80 KT 90 MPH 36H 09/0600Z 25.8N 88.7W 90 KT 105 MPH 48H 09/1800Z 28.1N 87.6W 95 KT 110 MPH 60H 10/0600Z 31.0N 87.3W 60 KT 70 MPH...INLAND 72H 10/1800Z 34.0N 87.5W 30 KT 35 MPH...POST-TROP/INLAND 96H 11/1800Z 37.5N 84.5W 15 KT 15 MPH...POST-TROP/INLAND 120H 12/1800Z...DISSIPATED