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Hurricane Barbara Discussion Number 9

Wiki-Hurricanes Forecast Center

8:00 PM PDT Mon Jul 1 2019

After an abrupt increase in strength this morning, Barbara has developed at a slower rate over the past few hours. The general composure of convection remains the same, with a large and deep central dense overcast juxtaposed with a prominent spiral band that persists south and west of the center. A ragged eye became evident on visible imagery around the time of the previous advisory, and this feature is now also apparent in infrared images. Satellite intensity estimates as of this writing are mixed: TAFB decreased from T4.5/77kt to T4.0/65kt, SAB increased from T4.0/65kt to T4.5/77kt, and UW-CIMSS ADT has risen to T4.6/80kt. I am unsure of what scene type TAFB used to arrive at a lower value. However, given the emergence of an eye on infrared imagery, I have decided to bump the initial intensity up to 80kt.

There is not a single noteworthy change with Barbara's track forecast. The hurricane is moving west-northwest and will continue on this path for the next 48 hours or so. After that, a weakening of the ridge will force the storm on a more northwest trajectory. By day 5, a re-intensification of the ridge combined with Barbara's weakening (thus allowing the low-level easterly trade wind belt across the East Pacific to become a prominent steering mechanism) will turn it west or even west-southwest.

There are a lot of questions surrounding Barbara's intensification forecast tonight. At face value, the environment remains favorable for rapid intensification, with wind shear at or below 10kt, ocean temperatures around or above 27C, and storm-centered mid-level relative humidity values at or above 80 percent for the next 72 hours or so. The culmination of these factors should set the stage for Barbara to become a major hurricane, and a significant one at that. The fly in the ointment continues to be the storm's large radius of maximum winds. Satellite animations this afternoon already show intermittent intrusions of dry air, and this is accentuated by a pretty ragged appearance on microwave imagery too. That being said, models remain nearly unanimous in Barbara reaching Category 4 strength, and the updated intensity forecast is barely changed from the previous one leading up to the cyclone's peak...for now. By days 4 and 5, hostile wind shear and a stable environment brought about by cold ocean temperatures are likely to cause rapid weakening, and the forecast intensities on those days have again been sharply reduced.

FORECAST MAX WINDS

INIT 02/0300Z 80 KT 90 MPH

12H 02/1200Z 100 KT 115 MPH

24H 03/0000Z 105 KT 120 MPH

36H 03/1200Z 115 KT 130 MPH

48H 04/0000Z 110 KT 125 MPH

72H 05/0000Z 90 KT 105 MPH

96H 06/0000Z 60 KT 70 MPH

120H 07/0000Z 35 KT 40 MPH

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