000 WTPZ42 KNHC 062032 TCDEP2 Tropical Storm Aletta Discussion Number 4 NWS National Hurricane Center Miami FL EP022018 300 PM MDT Wed Jun 06 2018 Aletta's cloud pattern has not become noticeably better organized during the day, and the banding features are not very well defined in enhanced infrared imagery. There is a dry intrusion over the northwest quadrant of the circulation with some restriction of the upper-level outflow over that quadrant as well. Dvorak classifications from both TAFB and SAB give a current intensity of 35 kt but a recent scatterometer pass indicated that the maximum winds are close to 40 kt, and that value will be used for the advisory intensity. Although the storm has not strengthened since early this morning, it is anticipated that the cyclone will be moving through fairly low vertical shear and over SSTs of 28 or 29 deg C during the next few days. This favorable environment should cause intensification. The official forecast, which is close to the simple or corrected model consensus guidance, continues to call for Aletta to become a hurricane by late Thursday or early Friday. High temporal and spatial resolution GOES-16 imagery suggested multiple low-level swirls near the estimated center position. Based on geostationary and microwave imagery along with the scatterometer data, the initial motion continues to be slowly westward or 270/7 kt. The flow on the south side of a mid-level ridge extending from Mexico into the eastern North Pacific should continue to steer Aletta westward to west-northwestward over the next few days. In 3-4 days, most of the track guidance shows the cyclone bending a little more to the right in response to a weakness in the ridge. As was the case in the previous cycle, the GFS shows the northernmost track and the ECMWF the southernmost. The official forecast lies between these extremes and is close to the model consensus. This is a tad slower than the previous NHC forecast. FORECAST POSITIONS AND MAX WINDS INIT 06/2100Z 14.2N 107.9W 40 KT 45 MPH 12H 07/0600Z 14.4N 109.0W 50 KT 60 MPH 24H 07/1800Z 14.5N 110.0W 55 KT 65 MPH 36H 08/0600Z 14.7N 111.0W 65 KT 75 MPH 48H 08/1800Z 15.0N 112.0W 70 KT 80 MPH 72H 09/1800Z 16.0N 113.6W 80 KT 90 MPH 96H 10/1800Z 17.3N 115.6W 70 KT 80 MPH 120H 11/1800Z 18.0N 117.0W 45 KT 50 MPH $$ Forecaster Pasch