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Hurricane Nora Forecast Discussion Number 12
2021-08-28 16:50:44| National Hurricane Center (East Pacific)
Issued at 1000 AM CDT Sat Aug 28 2021 000 WTPZ44 KNHC 281450 TCDEP4 Hurricane Nora Discussion Number 12 NWS National Hurricane Center Miami FL EP142021 1000 AM CDT Sat Aug 28 2021 Nora continues to show signs of strengthening with the center embedded beneath a Central Dense Overcast, where clouds tops are now as cold as -85 degrees Celsius. Dvorak fixes from TAFB and SAB are T4.0/65 kt and T4.5/77 kt, and the most recent objective numbers are near 75 kt. Nora's initial intensity is conservatively estimated to be 70 kt, but an Air Force Reserve Hurricane Hunter aircraft should help us verify the maximum winds later this afternoon. The latest fixes indicate that Nora is moving west of due north, or 350/10 kt. A shortwave trough over the northern Rockies has created a weakness in the subtropical ridge over the southwestern U.S., which should allow Nora to continue moving northward or north-northwestward through tonight. This motion will take Nora's center and hurricane-force winds very close to or over portions of Jalisco, Mexico, later today and this evening. On Sunday, the track guidance suggests that Nora will make a turn back toward the northwest, bringing the center over the Gulf of California by Monday at a much slower forward speed. The track guidance is in good agreement on this scenario, but the narrow width of the Gulf of California means that hazards away from the center could affect both the coast of mainland Mexico and the east coast of Baja California Sur. Due to this uncertainty, new watches and warnings have been extended northward along both coasts. The track guidance--and the NHC official forecast--suggest that Nora's center could move inland over Sonora, Mexico, in 4 to 5 days. Assuming Nora's center remains over water, low shear and warm waters should allow for additional strengthening during the next 24-36 hours. After that time, possible land interaction, influences of nearby topography, and potential ingestion of dry air from the Mexican plateau could all conspire to cause at least gradual weakening while Nora begins to move into the Gulf of California. That said, there is still a lot of uncertainty in the intensity prediction, and Nora is forecast to remain as a hurricane through early Tuesday, a scenario supported by the ECMWF model. One thing the models do agree on is that Nora's wind field should contract after it passes Cabo Corrientes and heads into the Gulf of California, and this is reflected in the NHC forecast. Key Messages: 1. Nora is forecast strengthen through tonight as it moves near the coasts of the Mexican states of Colima, Jalisco, Nayarit, and southern Sinaloa, and hurricane warnings are in effect for portions of that coastline. Interests in these areas and points farther north should closely monitor the progress of Nora and subsequent updates to the forecast. 2. Heavy rain associated with Nora is expected across the west coast of Mexico from the Mexican states of Guerrero, northward to southern Sonora, including Baja California Sur. This rain will likely result in life-threatening flash flooding and mudslides across these regions. Rainfall from Nora may spread into the southwestern U.S. and central Rockies during the middle to latter portion of next week. 3. Nora is forecast to move over the Gulf of California as a hurricane by Monday, bringing a risk of wind impacts to portions of the Mexican states of Baja California Sur, Sinaloa, and Sonora. Given the above-average uncertainty in the forecast intensity, confidence is not high enough to determine the magnitude and location of these potential impacts. FORECAST POSITIONS AND MAX WINDS INIT 28/1500Z 18.4N 105.4W 70 KT 80 MPH 12H 29/0000Z 20.1N 105.8W 75 KT 85 MPH 24H 29/1200Z 22.0N 106.5W 80 KT 90 MPH 36H 30/0000Z 23.1N 107.3W 80 KT 90 MPH 48H 30/1200Z 23.8N 108.0W 75 KT 85 MPH 60H 31/0000Z 24.5N 108.9W 70 KT 80 MPH 72H 31/1200Z 25.2N 109.6W 65 KT 75 MPH 96H 01/1200Z 26.9N 110.5W 60 KT 70 MPH 120H 02/1200Z 29.3N 111.0W 40 KT 45 MPH...INLAND $$ Forecaster Berg
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