000 WTPZ42 KNHC 071437 TCDEP2 Tropical Storm Aletta Discussion Number 7 NWS National Hurricane Center Miami FL EP022018 900 AM MDT Thu Jun 07 2018 The low-level center of Aletta has been somewhat difficult to locate this morning. Moderate westerly shear still appears to be affecting the tropical storm, and a recent SSMIS pass at 1329 UTC indicates that the low-level center is displaced slightly to the west of the mid-level center. A pronounced dry slot is present in IR and WV imagery, though a recent burst of convection near the center suggests that it may no longer be substantially inhibiting convection. Subjective Dvorak intensity estimates from TAFB and SAB at 1200 UTC were 55 kt, while objective estimates from SATCON and the ADT are around 60 kt. Given the increase of convection near the center since the TAFB and SAB classifications, the initial intensity has been raised to 60 kt. Little change has been made to the intensity forecast, which is slightly above the consensus guidance IVCN and HCCA, but below a mean of the dynamical hurricane models. The westerly shear currently affecting Aletta is expected to decrease over the next 12 to 24 hours, allowing the tropical storm to strengthen. By 48 hours, increasing shear and decreasing SSTs will likely induce a weakening trend that should accelerate through 72 h. Aletta will likely become a remnant low sometime near or just after 120 h. Aletta appears to have taken a slight turn toward the northwest this morning but the longer-term motion estimate is 290 at about 5 kt. Aletta will be steered generally west-northwest to northwestward over the next 5 days, with the largest source of uncertainty being how deep the circulation will be. A stronger, deeper cyclone will likely track farther north in response to an upper-level trough to the northwest, as shown by the GFS. A weaker cyclone will instead be steered more by the mid-level ridge to the north, and move on a heading closer to due west, as shown by the ECMWF. The NHC forecast splits these solutions, and is consistent with the intensity forecast which also is also lower than the GFS but well above the ECMWF. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 14.9N 109.3W 60 KT 70 MPH 12H 08/0000Z 15.1N 110.1W 65 KT 75 MPH 24H 08/1200Z 15.4N 111.0W 70 KT 80 MPH 36H 09/0000Z 15.8N 112.0W 75 KT 85 MPH 48H 09/1200Z 16.4N 112.7W 75 KT 85 MPH 72H 10/1200Z 17.6N 114.2W 60 KT 70 MPH 96H 11/1200Z 18.5N 116.0W 40 KT 45 MPH 120H 12/1200Z 18.5N 117.5W 30 KT 35 MPH $$ Forecaster Zelinsky