ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM Tropical Depression Aletta Discussion Number 24 NWS National Hurricane Center Miami FL EP022018 800 AM PDT Mon Jun 11 2018 Aletta has been devoid of any significant convection for about 8 hours due to the cyclone ingesting dry mid- and upper-level air along with an abundance of stable, low-level cold-air stratocumulus clouds. The combination of these unfavorable thermodynamic conditions and SSTs less than 26C beneath the cyclone should result in Aletta degenerating into a remnant low pressure system later today, possibly as early as the next advisory cycle. The initial intensity of 30 kt is based on an average of Dvorak T- and CI- numbers from TAFB, and an assumed spin down from the 35-kt winds noted in 0532 UTC ASCAT data. Microwave satellite fixes indicate that Aletta has been moving westward at about 10 kt since the previous advisory. However, this is likely just a temporary motion due to the decoupling of the low- and upper-level circulations owing to the loss of convection. As a result, the advisory motion is estimated to be a slower 270/06 kt. Aletta is expected to move westward today, followed by a turn toward the west-southwest by Tuesday due to the shallow cyclone being steered by the low-level easterly to northeasterly tradewind flow. By days 3 and 4, the steering flow is forecast to weaken significantly, causing Aletta to possibly stall, due to the remnant low coming under the influence of major Hurricane Bud's expanding circulation. The NHC track guidance is in good agreement on this developing track scenario, and the new forecast track is similar to the previous advisory and the consensus models HCCA and TVCN. FORECAST POSITIONS AND MAX WINDS INIT 11/1500Z 16.8N 117.8W 30 KT 35 MPH 12H 12/0000Z 16.7N 118.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 12/1200Z 16.5N 119.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 13/0000Z 16.3N 120.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 13/1200Z 16.1N 120.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 14/1200Z 16.0N 120.2W 15 KT 15 MPH...POST-TROP/REMNT LOW 96H 15/1200Z 16.0N 120.0W 15 KT 15 MPH...POST-TROP/REMNT LOW 120H 16/1200Z...DISSIPATED $$ Forecaster Stewart NNNN
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