ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM Tropical Storm Barbara Discussion Number 3 NWS National Hurricane Center Miami FL EP022019 900 PM MDT Sun Jun 30 2019 Barbara has continued to strengthen despite modest northwesterly mid-level vertical wind shear that has been undercutting a rapidly improving upper-level outflow pattern. Passive microwave satellite images over the past few hours indicate that the low-level center is displaced to the west of the coldest overshooting tops due to the aforementioned shear conditions. The initial intensity has been increased to 45 kt based on a consensus Dvorak intensity of T3.0/45 from TAFB and SAB, which is consistent with a late-arriving 1647Z ASCAT-C overpass that contained wind vectors of 41-42 kt. The initial motion is an unusually brisk 275/19 kt. A deep-layer ridge to the north of Barbara is expected to steer the tropical cyclone westward to west-northwestward for the next 48-72 hours, accompanied by a gradual decrease in forward speed. By 96 hours, a shortwave trough is forecast to weaken the ridge, allowing Barbara to turn more toward the northwest and gain some latitude. By day 5, however, the ridge is forecast to build back in behind the exiting trough, which should force the cyclone back on a west-northwesterly to westerly track. The latest track guidance continues to be tightly clustered with the HWRF remaining on the north side of the envelope and the ECMWF on the south side. The new NHC track forecast is similar to but a little south of the previous advisory track, and lies close to a blend of the TVCE, HCCA, and FSSE consensus models. The global models continue to forecast the deep-layer and mid-level vertical wind shear to steadily decrease from the current 15 kt to near 5 kt by 48-72 hours. The low shear conditions, along with SSTs of 28-29 deg C, should allow for at least steady strengthening for the next 48 h or so, followed by more significant strengthening in the 48-72 h time period. After that time, cooler water temperatures beneath the cyclone coupled with the strong inner-core wind field are expected to result in significant cold upwelling, which should induce steady weakening on days 4-5. Rapid intensification in the 24-72 h time frame is a distinct possibility, which would result in Barbara becoming a stronger major hurricane than currently forecast. The new official intensity forecast is a little more robust than the previous advisory, and follows a blend of the HCCA, ICON, and FSSE intensity consensus models. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 11.0N 114.2W 45 KT 50 MPH 12H 01/1200Z 11.5N 116.3W 55 KT 65 MPH 24H 02/0000Z 11.9N 119.0W 65 KT 75 MPH 36H 02/1200Z 12.3N 121.4W 75 KT 85 MPH 48H 03/0000Z 12.8N 123.5W 90 KT 105 MPH 72H 04/0000Z 14.0N 127.0W 105 KT 120 MPH 96H 05/0000Z 15.7N 130.7W 90 KT 105 MPH 120H 06/0000Z 16.8N 135.0W 75 KT 85 MPH $$ Forecaster Stewart NNNN