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Hurricane Flossie Winds: 75 kt
Pressure: 986 mbar
Advisory 12 / 8:00 AM PDT Wednesday, July 31, 2019

Flossie remains a bulbous storm this morning with an expansive and particularly cold central dense overcast that has not really changed in satellite presentation over the last six hours aside from slow growths in size. A collection of high-resolution microwave imagery from 10-12z tell the tale of a rain-free low-level center displaced about a half-degree northwest of the deepest convection, with the convection itself quite powerful but generally without organization. The mid-level eye discussed in the previous advisory was washed out by these convective updrafts. SSD analyzed T4.5/77kt as the current intensity. UW-CIMSS ADT assessed T4.3/72kt. AMSU extrapolated winds approximately ten hours ago were 70 kt but the pressures themselves suggested 80 kt winds. Based on these estimates and the fact that Flossie has not really changed at all, the initial intensity has been maintained at 75 kt, ending the streak of 5kt/6hr intensification.

The microwave data discussed earlier suggests that Flossie is in no hurry to intensify with the center exposed and characterized by highly ill-defined low-level banding. The primary culprit is an upper-level trough, set into motion by Hurricane Erick's outflow, whose axis is currently passing north of Flossie, resulting in an unfavorable 20 kt northerly flow and 15-25 kt deep-layer wind shear values. Sea surface temperatures are expected to gradually decline with marginal values below 27C setting in in about two days. Wind shear slackens some on days 2-3 before increasing again late in the forecast due to 300mb westerly flow from a tropical upper-tropospheric trough. It's hard to see Flossie doing much this afternoon, especially with its internal structure as disorganized as it is, and in fact some weakening may occur today. Some strengthening may occur as wind shear slackens, but a combination of unfavorables will work to limit intensification during this period. Weakening is shown at the end of the forecast due to increasing upper-level flow.

Not a whole lot to discuss in the track forecast as ridging remains in place, resulting in a general path towards the west-northwest. At days 4-5, ridging is expected to strengthen northeast of Hawaii, as well as troughing directly north of Hawaii. The interaction between these two features will dictate whether Flossie is able to cross into the Hawaiian Islands before curving northwards, or if this curve happens before the islands.

FORECAST MAX WINDS

INIT 31/1500Z 75 KT 85 MPH

12H 01/0000Z 75 KT 85 MPH

24H 01/1200Z 80 KT 90 MPH

36H 02/0000Z 85 KT 100 MPH

48H 02/1200Z 75 KT 85 MPH

72H 03/1200Z 70 KT 80 MPH

96H 04/1200Z 65 KT 75 MPH

120H 05/1200Z 50 KT 60 MPH

Forecaster Kalassak
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