Hurricane Paulette Discussion Number  26
NWS National Hurricane Center Miami FL       AL172020
500 AM AST Sun Sep 13 2020

Over the past 6 hours, conventional and passive microwave satellite 
data indicate that very little change to Paulette's overall 
convective cloud pattern and inner-core structure has occurred. 
A recent GMI pass indciated that the inner-core convection remains 
somewhat disheveled due to a narrow but pronounced band of dry air 
having penetrated the mid-levels of the cyclone. However, the 
low-level eye feature remains intact with a diameter of at least 30 
nmi. Given the little change in structure since the previous 
reconnaissance mission, the intensity is being maintained at 65 
kt. Another Air Force Reserve Hurricane Hunter aircraft will be 
investigating Paulette later this morning to provide a better 
estimate of the hurricane's intensity.

The initial motion estimate remains west-northwestward or 300/12 kt. 
Overall, there is no significant change to the previous track 
forecast or reasoning. The global and regional models are in 
excellent agreement on Paulette passing over or near Bermuda during 
the 24-36 hour period as the cyclone rounds a sharp east-to-west 
oriented subtropical ridge located near and due east of Bermuda. 
After passing Bermuda and moving north of the ridge in about 36 
hours, Paulette is forecast to accelerate northeastward ahead of an 
approaching deep-layer trough and associated surface cold front. 
There is one important feature to mention -- the official forecast 
track is west of the latest 0600 UTC interpolated models due to the 
interpolated model tracks taking the center of Paulette at least 30 
nmi east of Bermuda. In contrast, the GFS, UKMET, and ECMWF are less 
than 6 nmi apart at 12-48 hours, and that consensus brings the 
hurricane across or just west of Bermuda in about 30 hours. 
Therefore, the new NHC official track forecast is essentially just 
an update and extension of the previous advisory track, and lies 
just west of the tightly packed NHC guidance envelope.

Environmental conditions appear favorable to Paulette to strengthen 
during the next 72 hours or so, with only occasional intrusions of 
dry mid-level air briefly interrupting the intensification process. 
The ragged inner core structure will likely delay intensification 
this morning, but by the this afternoon and continuing into Monday, 
the vertical shear is forecast by the global models to decrease to 
near zero, which should allow for significant strengthening to 
occur. In fact, it highly probable that Paulette will continue to 
intensify as the hurricane passes over Bermuda. By 48 hours when the 
hurricane is expected to be north of Bermuda, baroclinic 
interaction with the aforementioned deep-layer trough is forecast 
to aid in the intensification process with Paulette possibly 
becoming a major hurricane around 72 hours. Thereafter, increasing 
vertical wind shear in excess of 25 kt should gradually weaken the 
cyclone. It is possible that by 96 hours or so, Paulette could merge 
with a frontal system and become a powerful extratropical low. For 
now, however, Paulette is forecast to remain just ahead of the 
front within the warm sector of a flat frontal wave. The official 
intensity forecast is similar to the previous advisory, and is near 
the upper end of intensity guidance throughout the 120-h forecast 
period.


Key Messages:

1. Paulette is expected to approach Bermuda as a hurricane on Sunday
and will be near the island Sunday night and Monday.  A prolonged
period of strong winds, storm surge, and heavy rainfall is expected
on Bermuda beginning Sunday evening, and a hurricane warning is in
effect for the island.  Preparations to protect life and property
should be rushed to completion.

2. Swells produced by Paulette are affecting portions of the
Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, and
the east coast of the United States. These swells could cause
life-threatening surf and rip current conditions.


FORECAST POSITIONS AND MAX WINDS

INIT  13/0900Z 29.4N  60.8W   65 KT  75 MPH
12H  13/1800Z 30.2N  62.5W   70 KT  80 MPH
24H  14/0600Z 31.8N  64.4W   80 KT  90 MPH
36H  14/1800Z 34.0N  65.0W   90 KT 105 MPH
48H  15/0600Z 35.9N  62.4W   95 KT 110 MPH
60H  15/1800Z 37.8N  57.9W   95 KT 110 MPH
72H  16/0600Z 39.3N  54.0W   90 KT 105 MPH
96H  17/0600Z 42.0N  46.0W   80 KT  90 MPH
120H  18/0600Z 43.8N  40.0W   65 KT  75 MPH

$$
Forecaster Stewart