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Tropical Storm Daniel Forecast Discussion Number 6
2018-06-25 10:39:39| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Mon Jun 25 2018 000 WTPZ45 KNHC 250839 TCDEP5 Tropical Storm Daniel Discussion Number 6 NWS National Hurricane Center Miami FL EP052018 200 AM PDT Mon Jun 25 2018 Cloud tops have been steadily warming since the previous advisory and the overall amount of convection has also been shrinking. However, a small mass of convection has persisted near and over the low-level center, and a 0443Z ASCAT partial pass indicated that the wind field in the western semicircle hadn't changed since the previous overpasses just 12 h prior. Therefore, it is assumed that winds near 40 kt still exists in the unsampled eastern semicircle. The last UW-CIMSS SATCON estimate at 0225Z was 43 kt. Based on the apparent lack of any significant low-level structural change noted in the latest ASCAT data, along with the SATCON estimate, the intensity is being maintained at 40 kt for this advisory. The initial motion estimate is 330/09 kt. Daniel is expected to gradually make a turn toward the northwest within the next 12 h as the small cyclone moves around the eastern periphery of a mid- to upper-level low located about 450 nmi to the west-southwest. As Daniel moves over progressively cooler waters, the weakening cyclone will become vertically more shallow and be steered westward by the low-level easterly tradewind flow on days 2-4. The latest model guidance remains good agreement with this developing track scenario. As a result, the new NHC track forecast is similar to the previous advisory track and is close to the consensus models TVCN and HCCA. The small cyclone is currently located over sea-surface temperatures (SST) of about 25C, with colder water lying ahead of the system. Although the vertical wind shear is forecast to be low, steady weakening and gradual erosion of the central convection is expected throughout the forecast period due to the colder SSTs and a lack of instability, especially after 12-18 hours. Daniel is forecast to weaken to a depression by 24 h, and degenerate into a remnant low pressure system shortly thereafter. However, given the current small and relatively weak circulation, faster weakening could occur than what is currently indicated. The latter scenario is supported by the ECMWF and UKMET models, which show dissipation by 72 hours. FORECAST POSITIONS AND MAX WINDS INIT 25/0900Z 18.8N 116.9W 40 KT 45 MPH 12H 25/1800Z 19.5N 117.8W 35 KT 40 MPH 24H 26/0600Z 20.2N 119.3W 30 KT 35 MPH 36H 26/1800Z 20.4N 121.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 27/0600Z 20.5N 122.8W 25 KT 30 MPH...POST-TROP/EXTRATROP 72H 28/0600Z 20.3N 126.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 29/0600Z...DISSIPATED $$ Forecaster Stewart
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