[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 270247
TCDAT3

Hurricane Franklin Discussion Number  26
NWS National Hurricane Center Miami FL       AL082023
1100 PM AST Sat Aug 26 2023

The eye of Franklin has been obscured in conventional satellite
imagery by deep convective bursts within its southern eyewall during
the past several hours. At times, there has been some disruption of
the inner core convection by drier air wrapping around the eastern
and northern portions of the circulation. Both the Air Force and
NOAA Hurricane Hunters investigated Franklin tonight and provided
useful data to analyze the storm. Tail Doppler radar data from the
NOAA aircraft reveal better vertical alignment of Franklin's vortex,
although there is still a bit of tilt with height. Peak SFMR wind
retrievals from both aircraft support an initial intensity of 75 kt,
and the latest dropsonde data indicate the surface pressure has
fallen to 975 mb.

Conditions appear favorable for some significant strengthening of
Franklin during the next couple of days. The deep-layer shear is
forecast to continue decreasing over the cyclone while it traverses
very warm SSTs greater than 29 deg C. The hurricane could be prone
to more rapid fluctuations in intensity given its small inner core,
and some of the rapid intensification (RI) guidance, particularly
DTOPS, suggests there are well above average chances that Franklin
could undergo RI during the next 48 h. Thus, the updated intensity
forecast is raised in the near term, bringing Franklin to major
hurricane strength in 24 h with a peak intensity of 115 kt on
Monday. This lies near HCCA and IVCN, but below some of the regional
hurricane models (HAFS and COAMPS-TC). Weakening is forecast at
days 4 and 5 as Franklin encounters increased shear over cooler
SSTs, but its wind field is expected to grow as it moves deeper into
the mid-latitudes.

The aircraft fixes indicate Franklin has continued to deviate left
of the forecast track, and its initial motion is northwestward at 7
kt. The near-term track forecast has been adjusted west of the
previous one based on Franklin's continued northwestward motion. A
broad high pressure ridge to the east of Franklin should steer the
hurricane more north-northwestward and northward during the next
couple of days. Later in the period, a deep-layer trough is expected
to move off the U.S. east coast, and most global models (except the
ECMWF) show Franklin becoming captured within the southwesterly flow
ahead of the trough and accelerating northeastward. The NHC forecast
track still shows the core of Franklin passing west and north of
Bermuda, but interests there should continue to monitor the latest
NHC forecast updates. By day 5, interaction with the upper trough
could bring about the start of extratropical transition.


FORECAST POSITIONS AND MAX WINDS

INIT  27/0300Z 23.9N  68.2W   75 KT  85 MPH
 12H  27/1200Z 24.9N  68.9W   85 KT 100 MPH
 24H  28/0000Z 26.2N  69.8W  100 KT 115 MPH
 36H  28/1200Z 27.6N  70.4W  110 KT 125 MPH
 48H  29/0000Z 29.2N  70.4W  115 KT 130 MPH
 60H  29/1200Z 30.8N  69.9W  115 KT 130 MPH
 72H  30/0000Z 32.5N  68.9W  105 KT 120 MPH
 96H  31/0000Z 35.8N  63.7W   90 KT 105 MPH
120H  01/0000Z 41.0N  52.5W   75 KT  85 MPH

$$
Forecaster Reinhart
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