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Tropical Storm Nicholas Forecast Discussion Number 1
2021-09-12 17:03:02| National Hurricane Center (Atlantic)
Issued at 1000 AM CDT Sun Sep 12 2021 000 WTNT44 KNHC 121502 TCDAT4 Tropical Storm Nicholas Discussion Number 1 NWS National Hurricane Center Miami FL AL142021 1000 AM CDT Sun Sep 12 2021 Showers and thunderstorms associated with a broad area of low pressure over the southern Bay of Campeche have increased overnight and very recently become better organized with a loose band of convection around the northeastern portion of the circulation. An Air Force Reserve reconnaissance aircraft that has been investigating the system has found 44-kt flight-level winds and SFMR winds that support a 35-kt initial intensity. Based on the recent increase in organization and the 35-kt initial intensity, advisories are being initiated on Tropical Storm Nicholas, the fourteenth named storm of the Atlantic hurricane season. The storm is located within an environment of moderate south-southwesterly vertical wind shear, over warm waters, and in a moist and unstable atmosphere. These conditions should allow gradual strengthening over the next 24 to 48 hours. The NHC intensity forecast follows suit and calls for gradual strengthening until the system reaches the coast of Texas. The official wind speed forecast is near the higher end of the guidance in best agreement with the SHIPS statistical guidance, the HFIP corrected consensus, and the HWRF. In this case, the intensity forecast is highly dependent on eventual track of the system. A track to the east of the NHC forecast could result in a lower wind shear environment and slightly more time over water for the system to strengthen. Conversely a track to the west of the forecast track would result in the system interacting with land much sooner. Since the system is still in its formative stage the initial motion estimate is a somewhat uncertain 330/11 kt. A north-northwestward motion around the western portion of a mid-level ridge that is sliding east near the coast of the Carolinas, should continue to steer Nicholas in that direction for the next 24 to 48 hours. After that time, steering currents weaken and the cyclone is expected to move slowly north-northeastward between a couple of mid-level ridges located to the east and west of Nicholas. The track guidance generally agrees with this overall scenario but there is some cross-track spread with the UKMET along the left side of the guidance envelope taking the storm into northeastern Mexico, while the GFS, HWRF, and HMON are along the right side. The NHC track is near the various consensus models and both the EC and GFS ensemble means. Key Messages: 1. Tropical storm conditions are expected along portions of the northeastern coast of Mexico and the coast of south Texas beginning on Monday. Nicholas is forecast to approach the middle Texas coast as a strong tropical storm on Tuesday, and tropical storm conditions are possible along portions of the middle and upper Texas coasts late Monday night and Tuesday. 2. There is the possibility of life-threatening storm surge along the coast of Texas from the Mouth of the Rio Grande to High Island. Residents in these areas should follow any advice given by local officials. 3. Periods of heavy rainfall are expected to impact portions of the Texas and Louisiana coasts today through the middle of the week. Significant rainfall amounts are possible, potentially resulting in areas of flash, urban, and isolated river flooding. FORECAST POSITIONS AND MAX WINDS INIT 12/1500Z 20.5N 94.8W 35 KT 40 MPH 12H 13/0000Z 21.9N 95.7W 40 KT 45 MPH 24H 13/1200Z 24.1N 96.6W 45 KT 50 MPH 36H 14/0000Z 26.4N 96.9W 50 KT 60 MPH 48H 14/1200Z 28.2N 96.5W 55 KT 65 MPH 60H 15/0000Z 29.4N 95.9W 40 KT 45 MPH...INLAND 72H 15/1200Z 30.3N 95.2W 30 KT 35 MPH...INLAND 96H 16/1200Z 31.0N 94.8W 25 KT 30 MPH...INLAND 120H 17/1200Z 32.0N 94.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown
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