Hurricane Flossie Winds: 70 kt
Pressure: 989 mbar
Advisory 10 / 8:00 PM PDT Tuesday, July 30, 2019

Flossie has strengthened this evening, although not in the prettiest fashion. Satellite animations show a large and amorphous central dense overcast, with little spiral banding and generally constricted upper-level outflow. Satellite intensity estimates are hovering around 65kt from SAB and UW-CIMSS ADT, while TAFB is higher at T4.5/77kt. As a compromise, the initial intensity is raised to 70kt.

Flossie's intensity forecast is, as it has been, a headache for us forecasters. The storm has developed an inner core according to recent microwave imagery, but it is not particularly well-defined. This is likely due to the impact of moderate wind shear, assessed around 10-15kt according to SHIPS. Compared to last night, the forecast for upper-level winds is starkly more hostile, with values over 25kt depicted tomorrow and no numbers under 10kt through the forecast period. This has resulted in a downward trend in most models, with statistical guidance showing little change in strength. The HWRF, which earlier predicted a Category 4 hurricane, continues to output a potent tropical cyclone, but even it has been on a general downward trend. Like I discussed before, this shear appears to be originating from a southward-diving PV streamer courtesy of Erick's outflow. I stated last night that the exact interaction between these two features would dictate Flossie's intensity forecast. Unfortunately for my verification, it appears that we are trending toward an unfavorable interaction that will limit Flossie's chances of becoming as powerful as once thought. Therefore, the updated intensity forecast is decreased from the previous one, although not as quickly as it probably should be to avoid large swings between advisories.

Flossie is moving west and should turn west-northwest soon as it explores the southern periphery of a broad mid-level ridge to its north. That west-northwest course will continue for the remainder of the forecast period, potentially sending Flossie toward the Hawaiian Islands after day 5.


INIT 31/0300Z 70 KT 80 MPH

12H 31/1200Z 75 KT 85 MPH

24H 01/0000Z 85 KT 100 MPH

36H 01/1200Z 95 KT 110 MPH

48H 02/0000Z 90 KT 105 MPH

72H 03/0000Z 80 KT 90 MPH

96H 04/0000Z 70 KT 80 MPH

120H 05/0000Z 60 KT 70 MPH

Forecaster TAWX14
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