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Tropical Storm John Discussion Number 20

Wiki-Hurricanes Forecast Center

8:00 AM PDT Fri Aug 10 2018

Cooling sea surface temperatures have made quick work of Tropical Storm John, and this morning satellite imagery shows no deep convection exists, with the coldest cloud tops now only a few specks of -30°C showers scattered in the stratiform remains of rainbands to the ciruclation's southwest. All in all, the once gargantuan hurricane has been reduced to a swirl of low-level clouds and decaying cirrus. SAB and TAFB current intensity estimates, which are more appropriate for weakening storms, reported T2.0/30kt and T3.0/45kt at 12z, while UW-CIMSS ADT has sunken to T2.0/30kt The most recent scatterometer pass at 0533z failed to resolve any gale-force winds, but missed a decent portion of the eastern semicircle. The expanse of the 30 kt wind field, however, seems suggestive of stronger winds still present, and as a blended value between SAB, TAFB, and ADT, a 35 kt value seems appropriate for John's intensity this morning.

With no new convection since last night, John is making its transition to a remnant low, and will likely be declared as such with the next advisory this afternoon as sea surface temperatures continue to fall, allowing John to gradually taper off in its post-tropical stages. John is currently drifting towards the west-northwest with the low-level tradewinds, and should do so for the next two days. The lingering fringes of an upper-level low with a weak low-level reflection over northern California should allow for a northward to northeastward turn towards California after 48 hours. However, John should be an inert cyclone by that time. However, moisture from John should spread across the state and perhaps provide much needed relief from the active wildfires currently ongoing.

MAXIMUM WINDS FORECAST

INIT 10/1500Z 35 KT 40 MPH

12H 10/0000Z 30 KT 35 MPH...POST-TROP/REMNT LOW

24H 11/1200Z 25 KT 30 MPH...POST-TROP/REMNT LOW

36H 11/0000Z 20 KT 25 MPH...POST-TROP/REMNT LOW

48H 12/1200Z 20 KT 25 MPH...POST-TROP/REMNT LOW

72H 13/0600Z...DISSIPATED