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Tropical Storm Flossie Discussion Number  15
NWS National Hurricane Center Miami FL       EP072019
500 PM HST Wed Jul 31 2019

Flossie is struggling this evening, with almost all of its deep
convection in the southeastern quadrant of the circulation. While
some thunderstorms have recently formed closer to the low-level
center, the bursts have not been able to maintain themselves due to
northwesterly shear.  Satellite intensity estimates are a consensus
55 kt, so that will be the initial wind speed.

The intensity forecast, as usual, is challenging this evening. Shear
is predicted to remain moderate/strong overnight, so some weakening
is shown then.  Afterward, while the upper-level wind pattern looks
like it will become more conducive for strengthening through
Saturday, the mid-level flow could keep the storm in a higher shear
environment than would be expected from only a simple 850-200 mb
shear calculation. Intensity models are also lower than the last
cycle; however, a few of the models make Flossie a hurricane again.
This isn't a particularly confident scenario, so it is usually
wise to be conservative when changing the forecast. Thus, the wind
speed forecast is only about 5 kt lower than the previous one
through 72 hours. The new NHC forecast is still higher than the
model consensus, especially at long range, and further downward
reductions are possible overnight if trends continue.

The storm continues to move westward at 14 kt, steered by a
deep-layer ridge that stretches across much of the eastern Pacific.
This ridge should steer Flossie westward to west-northwestward
during the next several days.  Model guidance shows less of a
reduction in forward speed during the next 5 days than the last
cycle, perhaps due to the now-weaker cyclone being more steered by
the lower-level flow. Thus the new forecast is faster than the
previous one, but lies basically along the previous NHC track. There
is considerable uncertainty in the 5-day position and intensity,
with average errors near 200 miles and 20 mph, respectively, so it's
best not to focus on specifics at that range.

FORECAST POSITIONS AND MAX WINDS

INIT  01/0300Z 14.3N 128.8W   55 KT  65 MPH
 12H  01/1200Z 14.7N 131.0W   50 KT  60 MPH
 24H  02/0000Z 15.4N 133.9W   55 KT  65 MPH
 36H  02/1200Z 16.0N 136.8W   55 KT  65 MPH
 48H  03/0000Z 16.6N 139.7W   60 KT  70 MPH
 72H  04/0000Z 17.7N 145.1W   65 KT  75 MPH
 96H  05/0000Z 18.5N 150.1W   60 KT  70 MPH
120H  06/0000Z 20.0N 154.5W   45 KT  50 MPH

$$
Forecaster Blake

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