ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM Tropical Storm Mario Discussion Number 4 NWS National Hurricane Center Miami FL EP142019 300 AM MDT Wed Sep 18 2019 Mario has done well in fighting off northeasterly shear that continues to impact it, with deep convection extending across the center for much of the night. A recent scatterometer pass indicated that tropical storm force winds now extend up to 80 n mi in the southeast quadrant, and 60 n mi in the northeast quadrant. This pass also indicated that the maximum winds have increased to 40 kt, and this will be the initial advisory intensity. Mario has turned a little to the left, and the initial motion is now 310/09 kt. A mid-level ridge to the northeast of the cyclone should continue to steer it in this general direction through Thursday morning. By late Thursday, a trough digging into the western United States is expected to erode the ridge, and the steering currents will collapse. This will result in a decrease in forward speed and eventually Mario is expected to become nearly stationary through Friday night. By Saturday, the ridge is forecast to rebuild over Mexico, which would result in Mario beginning a north-northwest motion. The official forecast track is high confidence through 72 hours and in the middle of tightly clustered consensus guidance. After 72 hours when the cyclone is expected to begin moving again, the guidance diverges and has shifted a little to the east. The official forecast was also shifted a little to the east, but remains west of the consensus aids during that time frame. The shear affecting Mario is expected to continue for the duration of the forecast period, while tropical cyclone Lorena remains to the northeast. Warm waters and a favorable atmospheric environment aside from the shear should allow for gradual strengthening for the next couple of days, and Mario is forecast to become a hurricane by Friday. By Saturday, Mario will begin to move into a drier and more stable environment, while the shear remains. This should cause a weakening trend to begin and continue through the end of the forecast period. The official forecast is similar to the previous one, and is on the higher end of the consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 18/0900Z 13.7N 110.1W 40 KT 45 MPH 12H 18/1800Z 14.7N 111.0W 45 KT 50 MPH 24H 19/0600Z 15.7N 112.2W 50 KT 60 MPH 36H 19/1800Z 16.4N 112.8W 60 KT 70 MPH 48H 20/0600Z 16.7N 113.0W 65 KT 75 MPH 72H 21/0600Z 17.5N 112.9W 65 KT 75 MPH 96H 22/0600Z 19.0N 113.6W 60 KT 70 MPH 120H 23/0600Z 21.0N 114.5W 55 KT 65 MPH $$ Forecaster Latto NNNN