Hurricane Sam

Tropical Storm Victor Forms, Watch In Effect As Hurricane Sam Nears Bermuda

Florida hurricane News weather
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FLORIDA: Both Systems Staying Away.

BY: WEATHER TEAM | BocaNewsNow.com

BOCA RATON, FL (BocaNewsNow.com) (Copyright © 2021 MetroDesk Media, LLC) — The National Hurricane Center early this morning issued a tropical storm watch for Bermuda as strong hurricane Sam nears the area. Sam is still in the midst of a turn and no threat to Florida. The system is packing winds of 145 MPH.

Hurricane Sam as of early Thursday morning, September 30, 2021.

Meantime, Tropical Storm Victor is also growing in strength. The system, which formed Wednesday, is also expected to maintain a path away from the United States mainland. Victor’s winds are 45 MPH and expected to increase to 75 MPH over the next day.

A third tropical system — expected just yesterday to form into a storm — is now unlikely to become much of anything. The system, marked by the yellow X above, has just a ten percent chance of development.

Tropical outlook for early Thursday, September 30, 2021.

The following is the early morning update for Sam, followed by the update for Victor.

Hurricane Sam Discussion Number  31
NWS National Hurricane Center Miami FL       AL182021
500 AM AST Thu Sep 30 2021

Sam is a very impressive hurricane in infrared satellite imagery
this morning. The 25-nm-wide eye remains very distinct and is
surrounded by a ring of convection with cloud tops around -65C.
The outflow is also well established in all quadrants. An Air Force
Reserve Hurricane Hunter aircraft that performed three eyewall
penetrations overnight has reported peak 700-mb flight-level winds
of 139 kt in the northeastern, southeastern, and eastern eyewall, 
and peak SFMR surface winds of 119 kt.  These data still support an
initial wind speed of 125 kt.  Sam's minimum pressure has fallen a 
few millibars since the NOAA aircraft mission last evening.  The 
latest estimated pressure from dropsonde data gathered by the Air 
Force is 937 mb. NOAA buoy 41044 has recently reported a peak 
one-minute wind of 68 kt with a gust to 86 kt in the northeastern 
eyewall of Sam.  The buoy has also reported peak seas of 40 ft. 

Sam could still strengthen a little today as it continues to move
over a warm ocean eddy and remains in low vertical wind shear
conditions.  After that time, difficult-to-predict eyewall cycles 
however, could cause some fluctuations in intensity. After 48 
hours, gradually decreasing SSTs and ocean heat content are likely 
to cause a more definitive weakening trend, with a faster rate of 
weakening likely after day 3. Sam is forecast to complete its 
extratropical transition by day 5, and it is predicted by the 
global model guidance to become a large and powerful extratropical 
low over the north Atlantic. 

Sam is moving northwestward or 320/10 kt. The track forecast 
reasoning is again unchanged from the previous advisory. Sam will 
move northwestward, and then northward around the western portion 
of a subtropical ridge during the next 48 hours.  After that time, 
Sam is predicted to turn northeastward between the ridge and a 
large mid-latitude trough over the northeastern United States. As 
that trough lifts northeastward by day 3, Sam is forecast to 
continue on a northeastward heading, but it is not likely to 
accelerate as much as a typical recurving tropical cyclone over 
the north-central Atlantic.  The dynamical model guidance remains 
in excellent agreement through 72 hours, but there is increasing 
spread after that time.  The latest runs of the GFS and ECMWF 
models have come into somewhat better agreement at days 3 through 
5, and the NHC track forecast is near the consensus of those 
typically reliable models. 

Although the core of Sam is forecast to pass east of Bermuda early 
Saturday, the tropical-storm-force wind field is forecast to expand 
and could pass very close to the island beginning late Friday night 
or early Saturday. Therefore, the Bermuda Weather Service has issued 
a Tropical Storm Watch for Bermuda. 


Key Messages:

1. Swells generated by Sam will impact the Northern Leeward Islands 
and the Greater Antilles, including Puerto Rico, during the next 
few days.  Swells are expected to reach Bermuda and the Bahamas by 
Friday, and then spread to the United States east coast by this 
weekend.  These swells could cause life-threatening surf and rip 
current conditions.  Please consult products from your local 
weather office.

2. Tropical storm conditions are possible on Bermuda beginning 
Friday night or early Saturday, and a Tropical Storm Watch has 
been issued for that island.


FORECAST POSITIONS AND MAX WINDS

INIT  30/0900Z 21.5N  59.1W  125 KT 145 MPH
 12H  30/1800Z 23.0N  60.2W  130 KT 150 MPH
 24H  01/0600Z 25.6N  61.4W  125 KT 145 MPH
 36H  01/1800Z 28.4N  61.8W  120 KT 140 MPH
 48H  02/0600Z 31.1N  61.3W  115 KT 130 MPH
 60H  02/1800Z 33.5N  59.9W  105 KT 120 MPH
 72H  03/0600Z 35.5N  58.0W   95 KT 110 MPH
 96H  04/0600Z 38.7N  52.6W   80 KT  90 MPH
120H  05/0600Z 44.3N  45.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
Tropical Storm Victor as of early Thursday morning, September 30, 2021.
Tropical Storm Victor Discussion Number   4
NWS National Hurricane Center Miami FL       AL202021
800 AM CVT Thu Sep 30 2021

Victor is gradually getting better organized.  AMSR2 microwave 
data from 0300 UTC showed that the low-level circulation has become 
more defined, with most convective banding features located west and
southwest of the center.  Victor's intensity is now estimated to be 
40 kt based on Dvorak estimates of T3.0 and T2.5 from TAFB and SAB, 
respectively, and objective numbers from UW-CIMSS around 40 kt.

Victor's vector is toward the west-northwest (290 degrees) at 11 
kt, and this heading should continue for the next 36 hours while 
the storm is located to the south a deep-layer ridge located over 
the subtropical eastern and central Atlantic.  In about 2 days, a 
mid- to upper-level low is forecast to develop over the central 
Atlantic, causing Victor to curve around the western periphery of 
the ridge, which gets shunted eastward between the Azores and the 
Canary Islands.  The track models are in generally good agreement 
on this scenario, and most of them are clustered tightly among each 
other.  Two notable exceptions, which are discounted at this time, 
are the HWRF and ECMWF models.  The HWRF, which is stronger than 
the other models, is way off to the east, while the ECMWF lies 
off to the south and west, a tendency that we've observed recently 
with other storms in the deep tropics.  The NHC track forecast is 
not changed much from the previous iteration and lies close to the 
GFS, HCCA, Florida State Superensemble, and TVCA solutions.

If the low-level circulation is in fact becoming better defined as 
shown by microwave imagery, Victor should be able to continue 
strengthening for the next couple of days in an environment of low 
vertical shear and over warm waters of roughly 28 degrees Celsius.  
The NHC intensity forecast is near the upper end of the guidance 
during this period and continues to show Victor reaching hurricane 
strength in about 36 hours.  Once the aforementioned mid- to 
upper-level low forms, strong southerly to southwesterly deep-layer 
shear is expected to develop over Victor and induce a weakening 
trend in about 3 days.  The intensity forecast has been lowered a 
bit during the latter part of the forecast period given the trends 
in the intensity models, but it is not as low as the HCCA and IVCN 
aids.  Interestingly, many of the global models suggest that the 
shear could be so strong that Victor might weaken to a depression 
or even degenerate into a remnant low by day 5.


FORECAST POSITIONS AND MAX WINDS

INIT  30/0900Z  8.7N  27.3W   40 KT  45 MPH
 12H  30/1800Z  9.4N  28.8W   50 KT  60 MPH
 24H  01/0600Z 10.2N  30.6W   60 KT  70 MPH
 36H  01/1800Z 11.2N  32.3W   65 KT  75 MPH
 48H  02/0600Z 12.6N  33.8W   65 KT  75 MPH
 60H  02/1800Z 14.4N  35.3W   60 KT  70 MPH
 72H  03/0600Z 16.6N  37.0W   55 KT  65 MPH
 96H  04/0600Z 22.0N  40.2W   40 KT  45 MPH
120H  05/0600Z 27.3N  41.9W   35 KT  40 MPH

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