Tropical Storm Narda Forecast Discussion Number 7
Issued at 200 AM MST Tue Sep 23 2025
000 WTPZ44 KNHC 230850 TCDEP4 Tropical Storm Narda Discussion Number 7 NWS National Hurricane Center Miami FL EP142025 200 AM MST Tue Sep 23 2025 Narda continues to strengthen well off the coast of southwestern Mexico this evening, with satellite imagery showing a central dense overcast and very cold cloud tops, colder than -80C, over the low-level center. A 0248 UTC GPM microwave pass and a 0350 UTC Metop-C ASCAT pass were helpful in estimating the center location, determining the motion, and assessing the structure of the cyclone. Subjective Dvorak estimates from TAFB and SAB were 4.0/65 kt and 3.5/55 kt, respectively, while objective estimates from UW-CIMSS ranged from 54 to 60 kt. A blend of these data, along with the improved satellite presentation, supports raising the initial intensity to 60 kt for this advisory. Narda is now estimated to be moving just south of due west, or 265 degrees, at 11 kt. A general westward motion is expected to continue during the next few days as the cyclone is steered by a strengthening subtropical ridge to its north and northwest. A turn toward the northwest and a decrease in forward speed are expected by days 4 and 5 as a mid-level low over southern California erodes the eastern portion of the subtropical ridge. The official forecast track has been adjusted slightly to the left of the previous forecast during the next couple of days to account for the south-of-due-west motion, and then slightly to the right of the prior forecast by days 4 and 5 due to an eastward shift in the guidance. The track forecast follows a blend of the HCCA, TVCE, and FSSE consensus aids, as well as the Google DeepMind/NOAA Eagle AI guidance. Narda will remain embedded within a moist air mass, over very warm waters, and in an environment of light to moderate easterly shear during the next day or so. These factors should support steady strengthening. The latest GFS- and ECMWF-based SHIPS guidance indicates about a 30 to 40 percent probability of a 25-kt increase within 24 hours, and the intensity forecast reflects this, with Narda expected to become a hurricane soon. Little change in strength is forecast between 36 and 60 hours as easterly shear increases to around 20–25 kt, which may disrupt the cyclone enough to prevent further intensification despite otherwise favorable conditions. Beyond 60 hours, shear is expected to decrease, which may allow Narda to approach major hurricane status before moving over cooler waters and into a drier mid-level environment by day 5. The official intensity forecast remains near the upper end of the guidance envelope and is most closely aligned with the HCCA aid. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 15.7N 106.1W 60 KT 70 MPH 12H 23/1800Z 15.5N 107.8W 75 KT 85 MPH 24H 24/0600Z 15.3N 109.8W 85 KT 100 MPH 36H 24/1800Z 15.2N 112.0W 90 KT 105 MPH 48H 25/0600Z 15.3N 114.3W 90 KT 105 MPH 60H 25/1800Z 15.6N 116.6W 90 KT 105 MPH 72H 26/0600Z 16.1N 119.0W 95 KT 110 MPH 96H 27/0600Z 17.5N 122.5W 95 KT 110 MPH 120H 28/0600Z 19.4N 123.5W 70 KT 80 MPH $$ Forecaster Jelsema (CPHC)
