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Hurricane Larry Discussion Number  26
NWS National Hurricane Center Miami FL       AL122021
1100 PM AST Mon Sep 06 2021
 
Larry has changed little in geostationary satellite imagery since 
the NOAA P-3 aircraft left the storm after 2130 UTC. Data from the 
mission showed that the hurricane possessed a very large wind field, 
and there were occasional hints in the flight-level wind data of an 
outer wind maxima trying to develop. The most recent passive 
microwave imagery from a 2148 UTC SSMIS pass showed some evidence of 
secondary bands forming away from the primary eyewall, though the 
inner eye remains large and distinct. Whether or not this will be 
the start of another eyewall replacement cycle (ERC) remains to be 
seen. For now, both the subjective Dvorak estimates from SAB and 
TAFB remain unchanged from earlier today, so Larry's intensity has 
been maintained at 110 kt for this advisory.

The hurricane continues to move to the northwest at 325/9 kt, guided 
along the southwestern periphery of a prominent subtropical ridge. 
Larry will reach the westward extent of this ridge in 60-72 hours as 
a large deep-layer trough approaches from the northeastern United 
States. The latest guidance now shows this trough capturing Larry 
towards the end of the forecast period, resulting in an abrupt 
acceleration to the northeast as the hurricane is steered by the 
strong westerly flow ahead of the mid-latitude trough. The track 
guidance continues to be in great agreement with Larry's forecast 
track, and only a few minor adjustments were needed to the most 
recent forecast, staying near the middle of the track guidance 
envelope. This latest forecast continues to show Larry passing to 
the east of Bermuda on Thursday. However, given Larry's large size, 
some impacts could still be felt even if the center passes well 
east, and a tropical storm watch could be needed for the island as 
soon as tomorrow morning.
 
The intensity forecast for Larry over the next few days is likely to 
be controlled by changes to its inner-core structure. If another ERC 
begins soon, this could result in a short-term drop off in maximum 
sustained winds as the hurricane's wind field expands. As mentioned 
last night, the broadening wind field, in combination with Larry's 
slow motion currently at 9 kt, could also result in more ocean 
upwelling closer to Larry's inner core. While the latest SHIPS 
guidance depicts warm sea-surface temperatures along the track of 
Larry over the next 2-3 days, the oceanic heat content in this part 
of the Atlantic basin is not very high. This might explain why the 
atmosphere-ocean coupled models (COAMPS-TC, HWRF, HAFS-B) show more 
significant weakening with a gradually decaying inner-core over 
cooler upwelled waters. The latest NHC intensity forecast is lower 
than the previous one, giving a bit more weight to the dynamically 
coupled hurricane models versus the statistical-dynamical guidance. 
However, even this latest forecast is higher than the reliable HFIP 
Corrected Consensus Approach (HCCA). Regardless of these intensity 
details, Larry is expected to remain a large and powerful 
hurricane over the next few days. 
 
Key Messages:
 
1. Large swells generated by Larry are affecting the Lesser Antilles 
and will spread to portions of the Greater Antilles, the Bahamas, 
and Bermuda tonight and tomorrow.  Significant swells should reach 
the east coast of the United States and Atlantic Canada by midweek 
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. Larry is forecast to approach Bermuda during the next few days as 
a large and powerful hurricane, bringing a risk of strong winds, 
heavy rainfall, and coastal flooding to the island by the middle of 
this week.  Interests in Bermuda should closely monitor the latest 
forecast updates during the next few days, and tropical storm 
watches could be needed for the island as soon as tomorrow.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/0300Z 23.1N  54.4W  110 KT 125 MPH
 12H  07/1200Z 24.1N  55.5W  105 KT 120 MPH
 24H  08/0000Z 25.6N  56.8W  100 KT 115 MPH
 36H  08/1200Z 27.3N  58.2W   95 KT 110 MPH
 48H  09/0000Z 29.2N  59.9W   95 KT 110 MPH
 60H  09/1200Z 31.6N  61.3W   90 KT 105 MPH
 72H  10/0000Z 34.6N  61.8W   90 KT 105 MPH
 96H  11/0000Z 44.0N  55.7W   80 KT  90 MPH
120H  12/0000Z 55.5N  43.4W   65 KT  75 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Papin
 
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