270 WTPZ45 KNHC 280258 TCDEP5 Hurricane Rosa Discussion Number 12 NWS National Hurricane Center Miami FL EP202018 800 PM PDT Thu Sep 27 2018 Rosa has continued to rapidly intensify during the past several hours, with a distinct and warm eye noted on satellite images along with deep eyewall convection. A blend of the latest Dvorak estimates gives an initial wind speed estimate of 125 kt, making Rosa the seventh category 4 hurricane of the very busy 2018 eastern Pacific hurricane season. It is worth noting that this value ties 2015 for the highest observed seasonal total in the basin during the satellite era. The hurricane still has a chance to intensify further given that it is still over warm waters within light shear. By the weekend, however, Rosa will encounter more marginal SSTs, and the shear will likely increase. These conditions should cause a significant weakening of the hurricane by early next week, and for Rosa to fall back to a tropical storm by Tuesday. The intensity forecast isn't particularly confident at long range because of the possibility of a trough interaction somewhat offsetting the effects of cool eastern Pacific waters and dry stable air. So far the guidance is fairly consistent, and the forecast continues to show steady weakening as Rosa approaches Baja California. Rosa continues moving at 265 deg, now at 8 kt. A mid-level ridge over the southwestern United States is forecast to weaken and move eastward over the next couple of days as a mean mid-tropospheric trough forms near the west coast of the US. This synoptic pattern should cause the tropical cyclone to gradually turn northward over that time, and eventually move to the northeast due to Rosa getting caught up into southwestern flow ahead of the trough. While there are still some notable speed differences in the model guidance, the overall trend is for a faster solution, which is consistent with a more vertically deep system feeling the stronger mid-level flow. The model consensus continues the faster trend, and the new forecast follows suit. FORECAST POSITIONS AND MAX WINDS INIT 28/0300Z 16.9N 116.7W 125 KT 145 MPH 12H 28/1200Z 17.1N 117.7W 130 KT 150 MPH 24H 29/0000Z 17.8N 118.4W 125 KT 145 MPH 36H 29/1200Z 19.0N 118.8W 115 KT 130 MPH 48H 30/0000Z 20.9N 118.8W 100 KT 115 MPH 72H 01/0000Z 25.0N 118.0W 75 KT 85 MPH 96H 02/0000Z 29.0N 115.5W 45 KT 50 MPH 120H 03/0000Z 36.0N 110.5W 25 KT 30 MPH...POST-TROP/INLAND $$ Forecaster Blake