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Tropical Storm Norbert Forecast Discussion Number 22
2020-10-14 10:37:08| National Hurricane Center (East Pacific)
Issued at 300 AM MDT Wed Oct 14 2020 000 WTPZ44 KNHC 140837 TCDEP4 Tropical Storm Norbert Discussion Number 22 NWS National Hurricane Center Miami FL EP192020 300 AM MDT Wed Oct 14 2020 Norbert continues to produce a concentrated area of deep convection, but it has been very difficult pinpointing the exact location of the center overnight. Earlier ASCAT data and an 0152 UTC SSMIS microwave overpass suggests that the center could be a little north of the previous estimates, but overnight shortwave infrared imagery and TAFB and SAB fixes still place it closer to the southern portion of the convective mass. The advisory position is a compromise between the various estimates, but leans toward the previous track out of respect for continuity. Dvorak estimates from TAFB and SAB support an intensity of 35 kt, which is used as the initial wind speed for this advisory. The earlier ASCAT overpass revealed some slightly stronger wind vectors, but these appear to have been rain inflated. The initial motion estimate is a somewhat uncertain 325/13 kt. Norbert is moving northwestward between a mid-level ridge over northern Mexico and a mid- to upper-level low to its northwest. This general heading should continue over the next 24 to 36 hours with some reduction in forward speed as Norbert begins to weaken and is steered by the weaker low-level flow. The dynamical models are in general agreement, but there are differences in how fast and far north Norbert will move. The models that maintain a deeper cyclone depict a more poleward motion. The NHC track leans toward the southern solutions by 24 hours since Norbert is likely to weaken and become a more vertically shallow system by that time. Norbert only has a short window of opportunity in which to strengthen this morning. After that time, increasing southwesterly shear and cooler sea surface temperatures should begin to weaken the tropical storm. Norbert is likely to become a remnant low in 24 to 36 hours as it encounters sea surface temperatures below 26C, moderate to strong shear, and a more stable atmosphere. The global models indicate that the low will dissipate within a couple of days, and the NHC forecast follows suit. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 22.1N 113.3W 35 KT 40 MPH 12H 14/1800Z 23.5N 114.3W 35 KT 40 MPH 24H 15/0600Z 24.9N 115.2W 30 KT 35 MPH 36H 15/1800Z 26.0N 115.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 16/0600Z...DISSIPATED $$ Forecaster Brown
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