Tropical Cyclone Discussion
517 WTPZ43 KNHC 022042 TCDEP3 Tropical Storm Marie Discussion Number 7 NWS National Hurricane Center Miami FL EP132026 200 PM MST Wed Sep 02 2026 Since the previous advisory, Marie has experienced bit of a hiccup in its convective structure, with warming clouds tops near the center aside from a recent burst wrapping around west of the center. The most recent microwave pass from this morning showed a banding type eye attempting to form, though it was struggling to close off on its northwest side. In addition, there was an RCM-3 SAR pass earlier today with an interesting structure, showing a small core, but with stronger winds occuring along the outer bands of Marie's circulation. This structure hints that it might take some time for the inner-core to fully consolidate. For now, the 18 UTC TAFB Dvorak satellite estimate was T3.5/55 kt, while the objective intensity estimates range from 53 to 67 kt. Thus, the initial intensity will remain 60 kt this advisory, keeping Marie just shy of hurricane intensity. Marie appears to be a little right of the prior forecast track, but is still moving off to the northwest, with the estimated motion at 310/10 kt. Over the next several days, a narrow mid-level ridge located to the north and northeast is expected to steer the tropical cyclone generally off to the west-northwest, gradually slowing its forward motion in the process as the ridge slowly weakens. Beyond 60 h, there continues to be significant cross-track spread that develops among the model guidance, related to how much an amplified mid-latitude trough, off the western United States coast, erodes this ridge. For this cycle, some of the more reliable track aids, ECMWF, Google DeepMind (GDMI), HCCA, actually show Marie turning back westward in the day 4-5 time frame, as the ridge holds to the north of the cyclone while the mid-latitude trough moves inland over the western United States. However, there remain a minority of solutions that show a more rightward track if the trough fully erodes the ridge steering Marie. The NHC track forecast this cycle is slightly right of the prior one for the first 48-60 h, following the latest trends in the GDMI and HCCA aids, but now bends a little more westward in days 4-5, also following trends in these aids. Intensity-wise, the earlier SAR imagery in addition to a partial ASCAT-C pass show Marie has a broad wind field with a larger-than-normal radius of maximum wind. This could prevent more rapid development over the next couple of days despite the favorable environmental conditions. Thereafter, while sea-surface temperatures (SSTs), diagnosed by SHIPS guidance between 27-28 C, appear favorable, some of these waters were recently churned up by the last tropical cyclone along this track (Iselle last week), and the HAFS-A/B hurricane-regional models suggest the large wind field of Marie could upwell some cooler waters underneath. Thus the latest NHC intensity forecast shows a somewhat lower intensity than earlier, peaking at 80 kt in the day 2-3 time frame. This intensity forecast favors the hurricane-regional models over the latest SHIPS guidance given the potential for ocean upwelling. Marie should be crossing the 26 C SST isotherm after 72 h, and weakening is expected to begin in earnest beyond this time period. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 18.0N 112.5W 60 KT 70 MPH 12H 03/0600Z 18.7N 113.5W 70 KT 80 MPH 24H 03/1800Z 19.5N 115.0W 75 KT 85 MPH 36H 04/0600Z 20.2N 116.5W 80 KT 90 MPH 48H 04/1800Z 20.8N 117.8W 80 KT 90 MPH 60H 05/0600Z 21.5N 119.1W 80 KT 90 MPH 72H 05/1800Z 22.1N 120.3W 75 KT 85 MPH 96H 06/1800Z 23.5N 122.5W 60 KT 70 MPH 120H 07/1800Z 23.7N 125.5W 50 KT 60 MPH