|
Show Selection: |
| #1249207 (Received by flhurricane at: 11:06 AM 22.Oct.2025) TCDAT3 Tropical Storm Melissa Discussion Number 5 NWS National Hurricane Center Miami FL AL132025 1100 AM EDT Wed Oct 22 2025 While Melissa continues to produce bursting convection on satellite imagery, with very cold cloud tops down to -95C, there is little evidence these convective bands are wrapping around the center. West-northwesterly shear of 20 to 25 kt is currently preventing the low-level and mid-level circulation centers from aligning. This downshear tilt with height has also been observed by the latest Air Force Reconnaissance mission, which reported significant winds at the surface in their most recent 850 mb center drop. The initial intensity for this advisory is held at 45 kt, taking a blend of recon observations which had a peak wind of 52 kt at 850 mb, and satellite intensity estimates from TAFB, ADT, and D-MINT. The wind field of Melissa also remains very asymmetric, as evidence of a recent 1040z RCM-1 Synthetic Aperture Radar pass showing the bulk of tropical-storm-force winds east of the center. The tropical storm has slowed down to a crawl this morning, with the estimated motion at 300/2 kt. The track forecast remains challenging today, and strongly related to the storm`s structure in the short-term. For the next 12-24 hours, Melissa is forecast to move very slowly to the northwest as it attempts to move into a weakness produced by an broad upper-level trough centered over the Bahamas. Whether or not it turns more rightward into this weakness is related to the vertical depth the various model guidance is depicting. The 06z GFS run, which is the model that has been on the right side of the guidance envelope for days, shows a more vertically coherent system over the next 24-48 hours, and causes Melissa to abruptly turn northeastward over the next 48 hours. While this appears to be an outlier solution, the Google DeepMind ensemble mean (GDMI) also shows this northeastward motion, and a significant fraction of its ensemble members show the Melissa making landfall on the Island of Hispaniola. However, the remainder of the track guidance, including the ECMWF and its ensemble mean, suggest that Melissa will remain misaligned and move more slowly north-northwest over the next couple of days. The NHC track solution slightly favors the latter scenarios, lying just east of the ECMWF mean, out of respect of the reliable GDMI aid. After about 60 h, mid-level ridging begins to build back in to the north, and most of the guidance responds by showing a sharp turn westward, albeit still at a snail`s pace. The overall track guidance, GFS and GDMI excluded, has shifted left this cycle beyond 72 h, and the NHC track was shifted in that direction, but not as far south and west as the HAFS-A/B regional models. It goes without saying, this is a very challenging track forecast. The intensity forecast has its own share of challenges. At least in the short-term, vertical wind shear is expected to persist between 20 to 30 kt, and will likely prevent Melissa from becoming fully aligned and taking advantage over the very warm 30-31C sea surface temperatures. After about 48 hours, the GFS and ECMWF-based SHIPS guidance shows the shear decreasing gradually, but the timing on when the system becomes more vertically coherent varies among both the global and hurricane-regional model guidance. Most of the guidance shows significant or even rapid intensification in days 3-5, and the NHC intensity forecast was raised once again during this time frame, but not as high as the HCCA or hurricane-regional models due to continuity constraints to the previous forecast. The day 5 forecast now shows Melissa becoming a major hurricane, and further upward adjustments may be necessary in subsequent cycles. The intensity forecast is also more uncertain than usual, in large part related to the track uncertainty. Key Messages: 1. Melissa is expected to produce heavy rainfall across portions of the Dominican Republic, Haiti, and Jamaica through this weekend, bringing a risk of significant flash flooding and landslides. 2. Hurricane conditions are possible in the southwestern peninsula of Haiti where a Hurricane Watch is in effect. A Tropical Storm Watch is in effect for Jamaica. Preparations to protect life and property should be completed by Thursday. 3. There is significant uncertainty in the track and intensity forecast of Melissa. Interests elsewhere in Hispaniola and Cuba should continue to monitor the latest forecasts. FORECAST POSITIONS AND MAX WINDS INIT 22/1500Z 14.4N 73.6W 45 KT 50 MPH 12H 23/0000Z 14.8N 73.9W 45 KT 50 MPH 24H 23/1200Z 15.2N 74.3W 50 KT 60 MPH 36H 24/0000Z 15.6N 74.4W 55 KT 65 MPH 48H 24/1200Z 16.0N 74.4W 55 KT 65 MPH 60H 25/0000Z 16.3N 74.6W 60 KT 70 MPH 72H 25/1200Z 16.5N 74.9W 70 KT 80 MPH 96H 26/1200Z 16.6N 75.8W 90 KT 105 MPH 120H 27/1200Z 16.4N 77.4W 105 KT 120 MPH $$ Forecaster Papin |
