ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM Tropical Storm Aletta Discussion Number 20 NWS National Hurricane Center Miami FL EP022018 800 AM PDT Sun Jun 10 2018 Shortly after 0600Z, a strong burst of deep convection, containing very cold cloud top temperatures of -90C and significant lightning activity, developed northwest of the previously exposed low-level circulation center. The center has since made a jog toward the northwest closer to the strongest convection. The initial intensity has been decreased to 40 kt, based on average of TAFB current intensity (CI) and the current T-number estimates. Although the general trend for the next 24 h or so should be a gradual erosion of the deep convection due to the entrainment of drier and more stable air and the cyclone moving over SSTs less than 26C. However, there will likely be intermittent bursts of convection that will slow the weakening rate and maintain Aletta as a tropical cyclone. By 36 h and beyond, increasing southwesterly vertical wind shear of 15-20 kt, coupled with the aforementioned stabilizing environment, should cause all convection to dissipate, resulting in Aletta becoming a shallow remnant low pressure system. The new NHC intensity forecast is similar to the previous advisory, and closely follows the HCCA and IVCN consensus intensity models. Despite the recent northwestward jog, the average motion over the last 36 h yields a motion of 280/05 kt, similar to the previous advisory motion. Aletta is forecast by most of the model guidance to move westward to west-northwestward, or around 280/05 kt for the next 24 h or so. After that, a weak low- to mid-level ridge to the north of the cyclone is expected to build southward slightly, forcing the weak and shallow cyclone toward the west-southwest. By days 4 and 5, the system could stall as it comes under the increasing influence of strengthening Tropical Storm Bud, currently located about 700 nmi to the east-southeast. The official forecast track is similar to the previous advisory and is in the middle of the track model guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 16.5N 115.1W 40 KT 45 MPH 12H 11/0000Z 16.6N 116.0W 35 KT 40 MPH 24H 11/1200Z 16.7N 117.2W 30 KT 35 MPH 36H 12/0000Z 16.6N 118.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 12/1200Z 16.4N 119.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 13/1200Z 16.2N 120.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 14/1200Z 16.0N 120.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 15/1200Z 15.8N 121.0W 15 KT 15 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart NNNN
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Page last modified: Monday, 31-Dec-2018 12:10:12 UTC