Tropical Storm Flossie Winds: 60 kt
Pressure: 992 mbar
Advisory 8 / 8:00 AM PDT Tuesday, July 30, 2019

Flossie's areal extent has been increasing this morning, with the central dense overcast discussed last advisory persisting, albeit not particularly with well-defined symmetry. A high-resolution AMSR2 microwave pass at 0940z revealed that the low-level center of circulation was displaced slightly north of the deepest convection, with only narrow low-level banding within the northern semicircle. SAB estimated T4.0/65kt while TAFB estimated T3.5/55kt. Automated estimates from UW-CIMSS ADT indicated T3.6/57kt. An average of these estimates indicates a slight uptick in the intensity to 60 kt, and given that all of these were good fixes, the initial intensity is set to 60 kt in concurrence.

Motion to the west-northwest is generally expected throughout the next five days, with the same west-northwest to west curvature due to rebuilding ridging late in the forecast that has been repeated ad nauseum in this basin.

What's more complex is the intensity forecast, and the 12z model suite has no semblance of consensus. What we do know is that, at least in the short term, conditions are favorable for intensification, with all the traditional parameters generally favorable (shear is sitting at a manageable 10 kt), and there's an upper trough up ahead providing a zone of diffluence. The more challenging uncertainty arises in how Flossie interacts with the trough, especially upstream where there's going to be northerly flow and resultant wind shear. This interaction is going to predicate on how well Flossie organizes beforehand. If you take a robust system like the HWRF able to blast away at impinging upper-level flow, Flossie will largely maintain its intensity. Otherwise, you might see something like SHIPS which depicts a decline (perhaps too precipitously so). I can envision the likelihood of a rapid intensification event tonight, well-timed with a southward dip in the track that these types of storms love, and I think it's decently likely we'll be looking at a Category 2 hurricane tomorrow morning. After this the jury is still up regarding the trough's effects. I have largely continued to slow weakening we've been depicting in prior advisories, but this is definitely not to suggest we have high confidence in this depiction. The primary changes here are in the short-term, where I've slightly elevated some of the day 1 figures.


INIT 30/1500Z 60 KT 70 MPH

12H 31/0000Z 70 KT 80 MPH

24H 31/1200Z 85 KT 100 MPH

36H 01/0000Z 95 KT 110 MPH

48H 01/1200Z 90 KT 105 MPH

72H 02/1200Z 90 KT 105 MPH

96H 03/1200Z 80 KT 90 MPH

120H 04/1200Z 70 KT 80 MPH

Forecaster TheAustinMan
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