000 WTPZ43 KNHC 070845 TCDEP3 Tropical Storm Cosme Discussion Number 4 NWS National Hurricane Center Miami FL EP032019 200 AM PDT Sun Jul 07 2019 Dry air appears to be taking its toll on Cosme. Deep convection mostly dissipated earlier tonight and water vapor imagery shows very dry air impinging on the northwestern side of the cyclone, and wrapping into the southern semicircle of the circulation. There has been some new convection developing about 100 n mi northeast of the center over the past few hours, which is likely associated with the approaching diurnal convective maximum time period. A recent scatterometer pass that partially captured Cosme's wind field indicated weakening had occurred over the western portion of the cyclone over the past several hours which suggests that an overall weakening trend has begun. Therefore the initial intensity has been lowered to 35 kt and this is in agreement with the latest TAFB and ADT satellite intensity estimates. Cosme will continue to battle dry air while moving over marginally favorable SSTs today. There is a chance for the regenerating convection to expand toward the cyclone's center over the next several hours, thus prolonging the time Cosme will remain a tropical storm. However, later today the cyclone will begin to cross the 26 C isotherm and also will enter an even drier environment. This should cause Cosme to weaken to a tropical depression. Thereafter, the dry air and cooler SSTs will cause Cosme to become devoid of deep convection and the cyclone should degenerate into a remnant low either by tonight, or on Monday. The latest official intensity forecast shows a weakening trend that is a little faster than previously forecast, and is in agreement with the latest intensity guidance as well as model simulated satellite imagery. Cosme continues on a generally west-northwest track, and has slowed slightly to around 9 kt. The cyclone will be steered toward a weakness in the subtropical ridge developing to its northwest over the next couple of days while gradually decreasing in forward speed. The latest track guidance is close to the previous forecast and near the consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 16.9N 118.0W 35 KT 40 MPH 12H 07/1800Z 17.6N 119.1W 30 KT 35 MPH 24H 08/0600Z 18.4N 120.3W 25 KT 30 MPH 36H 08/1800Z 19.1N 121.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 09/0600Z 19.7N 121.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 10/0600Z...POST-TROP/REMNT LOW $$ Forecaster Latto/Pasch