[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 081453
TCDAT2

Hurricane Larry Discussion Number  32
NWS National Hurricane Center Miami FL       AL122021
1100 AM AST Wed Sep 08 2021

Larry's eye has been only faintly apparent on recent satellite
imagery, but the hurricane is still maintaining a fair amount of
deep convection near/around the center.  An Air Force Reserve Unit
Hurricane Hunter aircraft investigated Larry a little while ago and
observations found that the central pressure has risen only slightly
since yesterday, with peak flight level winds of 118 kt in the
northeastern quadrant.  However, the highest SFMR-observed surface
winds were only 75 kt, indicating that the strong winds aloft are
not very effectively being transported to the surface.  Given this,
along with the slightly-degraded appearance of the system, the
current intensity is reduced to 95 kt, which is just a bit above the
latest subjective and objective Dvorak estimates.

The hurricane is moving northwestward at a slightly faster clip, or
320/11 kt.  Over the next 36 to 48 hours, Larry is expected to move
around the western periphery of a subtropical high pressure area
and pass to the east of Bermuda.  Thereafter, the cyclone should
accelerate northeastward ahead of a deep-layer trough moving through
the northeastern United States and become embedded within the
mid-latitude southwesterly flow.  This will take Larry near or over
southeastern Newfoundland in 60-66 hours and then over the far
North Atlantic.  The official forecast track has not changed
significantly from those in the previous few advisories, and
remains close to the dynamical model consensus, TVCA.

Larry should remain in an environment of low vertical shear and
warm surface waters for the next 36-48 hours.  However, the oceanic
heat content beneath the hurricane should be gradually decreasing
during the next few days.  Only slow weakening is forecast, similar
to the latest NOAA corrected consensus, HCCA, prediction.  In about
72 hours, the global models indicate that Larry will become
embedded within a frontal zone, so the NHC forecast shows it as an
extratropical cyclone by that time.  In 5 days or less, the system
is expected to merge with another large cyclone at high latitudes.

Key Messages:

1. Large swells generated by Larry will continue to affect the
Leeward Islands, portions of the Greater Antilles, the Bahamas and
Bermuda.  Significant swells will begin to reach the east coast of
the United States and Atlantic Canada later today and continue
affecting these shores through the end of the week.  These swells
will likely cause life-threatening surf and rip current conditions,
and beachgoers and other interests along these coasts are urged to
follow the guidance of lifeguards and local officials this week.

2. The center of Larry is forecast to pass east of Bermuda on
Thursday, but given Larry's large size, tropical storm conditions
are expected there there Thursday, along with a risk of coastal
flooding.  A Tropical Storm Warning is in effect for Bermuda, and
interests there should closely monitor the latest forecast updates.

3. Larry is forecast to move near or over portions of southeastern
Newfoundland late Friday and Friday night as it undergoes transition
to a hurricane-force post-tropical cyclone. There is an increasing
risk of impacts from high winds, rainfall, and storm surge in
portions of Newfoundland, and interests there should monitor updates
to the forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 27.7N  58.3W   95 KT 110 MPH
 12H  09/0000Z 29.1N  59.6W   95 KT 110 MPH
 24H  09/1200Z 31.6N  61.3W   95 KT 110 MPH
 36H  10/0000Z 34.7N  61.9W   90 KT 105 MPH
 48H  10/1200Z 39.1N  60.4W   85 KT 100 MPH
 60H  11/0000Z 44.4N  55.6W   80 KT  90 MPH
 72H  11/1200Z 50.5N  49.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  12/1200Z 61.0N  37.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
120H  13/1200Z...MERGED

$$
Forecaster Pasch

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