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Tropical Storm Kristy Discussion Number 2

Wiki-Hurricanes Forecast Center

2:00 AM PDT Tue Aug 7 2018

Tropical Depression Thirteen-E has become better organized since the previous advisory, with the well-defined center of circulation well positioned within deep convection according to a 0506Z SatSCAT pass. There are signs of an eye-like feature on more recent infrared images, though this may be exacerbated by dry air intrustions. Satellite intensity estimates were T2.0/30kt from SAB/TAFB/UW-CIMSS ADT, but given the increase in organization since the previous advisory, plus numerous 35kt barbs on the SatSCAT pass, the initial intensity has been set to 35kt, and Thirteen-E has been upgraded to Tropical Storm Kristy.

Wind shear is currently on the over side of 15kt, but recent projections from SHIPS suggest this may decrease to under 10kt between 36hr and 96hr. Mid-level relative humidity values start off around 65 percent, falling to near 40 percent by the end of the period. Ocean temperatures, meanwhile, are expected to remain over 27C for the next 24 hours and remain near 26C through 72 hours before decreasing further thereafter. The SHIPS and LGEM indicate peak intensities of 56kt and 50kt, respectively, while the GFS and HWRF continue to make Kristy a hurricane. The ECMWF and UKMET are not interested in the system still. The bottom line is that while rapid intensification does not appear to be imminent, steady intensification should bring Kristy to strong tropical storm strength in about 72 hours. Thereafter, cold waters, drier air, and increasing shear should cause the storm to weaken, degenerating to a remnant low around day 5.

Kristy is moving west on the south side of a mid-level ridge that stretches across the subtropical Pacific and into the Southwestern United States. A weakness in this ridge should become apparent in about 2 days as John moves west of Baja California, and assuming Kristy intensifies as forecast, this weakness should be enough to draw the storm northward. The GFS shows Kristy and John rotating around one another by day 5, whereas the ECMWF with its shallow depiction sends Kristy west in the general direction of Hawaii. Given our forecast, the GFS seems to be the more likely winner in this scenario.

FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 35 KT 40 MPH

12H 07/1800Z 40 KT 45 MPH

24H 08/0600Z 45 KT 50 MPH

36H 08/1800Z 50 KT 60 MPH

48H 09/0600Z 55 KT 65 MPH

72H 10/0600Z 60 KT 70 MPH

96H 11/0600Z 50 KT 60 MPH

120H 12/0600Z 35 KT 40 MPH...POST-TROP/REMNT LOW