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Major Hurricane Sam


Jtm12180
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15 hours ago, Windspeed said:
15 hours ago, sojitodd said:
And the debate is getting a bit nasty too. Maybe it is anger that Sam and these two storms to follow will be only for the fishes?

I mean, whatever. I am sure there are plenty that only follow for landfalls. I enjoy tracking them regardless. This has already been a better CV season than last year with Larry (which did landfall) and Sam, the strongest MDR system since Lorenzo. 2020 Paulette was kind of meh. Really, Teddy was the only quality MDR system last year. At any rate, it's far from dead or boring.

I agree especially with what we have had already let's just follow and enjoy the fish storms. Maybe a close call for Bermuda or something for some excitement- and they are built for that kind of thing it seems so they will be fine with a close call. 

We may be following stuff in the Caribbean through December anyways there is plenty of time left as well.

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14 minutes ago, Windspeed said:

Sam is looking downright impressive this morning. Also crossing a region of higher OHC, with SSTs surpassing 29°C. Definitely going to keep pumping out that ACE at least thought tomorrow.
236e0ac41f88fdf342a6591b144e9ceb.gif

What is the record for ACE for a single storm in the Atlantic Basin?

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28 minutes ago, bigtenfan said:

What is the record for ACE for a single storm in the Atlantic Basin?

Wikipedia states it was a little known 1899 long duration Cat 4; Ivan, Irma, and Isabel place too [hmmm, something about 'Is'?].

I think Sam is going to be pretty high on ACE despite it's so far small size. Sam has been a named storm for eight days now and will probably go on another eight to ten days at least [NHC is on TCDAT3/FcstDisc #28 this morning, how many more to go?].:

Quote

The highest ever ACE estimated for a single storm in the Atlantic is 73.6, for the San Ciriaco hurricane in 1899, likely because it was a Category 4 hurricane which lasted for 4 weeks. This single storm had an ACE higher than many whole Atlantic storm seasons. Other Atlantic storms with high ACEs include Hurricane Ivan in 2004, with an ACE of 70.4, Hurricane Irma in 2017, with an ACE of 64.9, the Great Charleston Hurricane in 1893, with an ACE of 63.5, Hurricane Isabel in 2003, with an ACE of 63.3, and the 1932 Cuba hurricane, with an ACE of 59.8.[8]

Individual storms in the Atlantic

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3 hours ago, STxVortex said:

Wikipedia states it was a little known 1899 long duration Cat 4; Ivan, Irma, and Isabel place too [hmmm, something about 'Is'?].

I think Sam is going to be pretty high on ACE despite it's so far small size. Sam has been a named storm for eight days now and will probably go on another eight to ten days at least [NHC is on TCDAT3/FcstDisc #28 this morning, how many more to go?].:

Individual storms in the Atlantic

Thanks so much

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Is that a bit of dry air that got entrained in on this pic. It is the last in the current loop from Tropical tidbits
 
image.thumb.png.d33c0b380a45d97d0e759e332cc0c179.png
That's a dry slot due to subsidence by the stronger outer eyewall. The inner eyewall was still experiencing convective bursts, though continuing to decay. A larger eye is now clearing as the old cloud debris dissipates.

Sam is getting mean. Last recon pass supports a ~125 kt hurricane. Satellite continues to improve with a deep convective band on the SW periphery of the CDO.358ed3d10602945358c8d2d60cdb8b3a.jpg
d82e9c5144b0b83c4ebea8bf3e4e17a0.gif
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16 minutes ago, Windspeed said:

That's a dry slot due to subsidence by the stronger outer eyewall. The inner eyewall was still experiencing convective bursts, though continuing to decay. A larger eye is now clearing as the old cloud debris dissipates.

Sam is getting mean. Last recon pass supports a ~125 kt hurricane. Satellite continues to improve with a deep convective band on the SW periphery of the CDO.358ed3d10602945358c8d2d60cdb8b3a.jpg
d82e9c5144b0b83c4ebea8bf3e4e17a0.gif

This is one of the great examples in recent memory for me at least of being able to merge days of recon data and satellite/microwave data. This’ll be great for researchers. 

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Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 30th day of the month at 4:27Z
Agency: United States Air Force 
Aircraft: Lockheed WC-130J Hercules with reg. number AF96-5302 
Storm Name: Sam
Storm Number & Year: 18 in 2021 (flight in the North Atlantic basin)
Mission Number: 13
Observation Number: 03 ( See all messages of this type for this mission. )

A. Time of Center Fix: 30th day of the month at 4:02:10Z
B. Center Fix Coordinates: 20.71N 58.58W
B. Center Fix Location: 513 statute miles (826 km) to the ENE (72°) from San Juan, Puerto Rico (U.S.).
C. Minimum Height at Standard Level: 2,594m (8,510ft) at 700mb
D. Minimum Sea Level Pressure: 943mb (27.85 inHg)
E. Dropsonde Surface Wind at Center: From 360° at 10kts (From the N at 12mph)
F. Eye Character: Closed
G. Eye Shape: Elliptical (oval shaped)
G. Orientation of Major Axis in Elliptical Eye: 200° to 20° (SSW to NNE)
G. Length of Major Axis in Elliptical Eye: 30 nautical miles (35 statute miles)
G. Length of Minor Axis in Elliptical Eye: 26 nautical miles (30 statute miles)
H. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 111kts (127.7mph)
I. Location & Time of the Estimated Maximum Surface Wind Inbound: 7 nautical miles to the WSW (252°) of center fix at 4:00:00Z
J. Maximum Flight Level Wind Inbound: From 353° at 120kts (From the N at 138.1mph)
K. Location & Time of the Maximum Flight Level Wind Inbound: 10 nautical miles (12 statute miles) to the WSW (251°) of center fix at 3:59:00Z
L. Estimated (by SFMR or visually) Maximum Surface Wind Outbound: 99kts (113.9mph)
M. Location & Time of the Estimated Maximum Surface Wind Outbound: 23 nautical miles (26 statute miles) to the NE (49°) of center fix at 4:09:00Z
N. Maximum Flight Level Wind Outbound: From 140° at 139kts (From the SE at 160.0mph)
O. Location & Time of the Maximum Flight Level Wind Outbound: 17 nautical miles (20 statute miles) to the NE (50°) of center fix at 4:07:00Z
P. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 9°C (48°F) at a pressure alt. of 3,050m (10,007ft)
Q. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 18°C (64°F) at a pressure alt. of 3,030m (9,941ft)
R. Dewpoint Temp (collected at same location as temp inside eye): 14°C (57°F)
R. Sea Surface Temp (collected at same location as temp inside eye): Not Available
S. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
S. Fix Level: 700mb
T. Navigational Fix Accuracy: 0.02 nautical miles
T. Meteorological Accuracy: 1 nautical mile

Remarks Section:
 

Maximum Flight Level Wind: 139kts (~ 160.0mph) which was observed 17 nautical miles (20 statute miles) to the NE (50°) from the flight level center at 4:07:00Z
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BULLETIN
Hurricane Sam Advisory Number  31
NWS National Hurricane Center Miami FL       AL182021
500 AM AST Thu Sep 30 2021

...POWERFUL HURRICANE SAM CONTINUES NORTHWESTWARD...
...TROPICAL STORM WATCH ISSUED FOR BERMUDA...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...21.5N 59.1W
ABOUT 345 MI...555 KM NE OF THE NORTHERN LEEWARD ISLANDS
ABOUT 825 MI...1325 KM SSE OF BERMUDA
MAXIMUM SUSTAINED WINDS...145 MPH...230 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...937 MB...27.67 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The Bermuda Weather Service has issued a Tropical Storm Watch for
Bermuda.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Watch is in effect for...
* Bermuda

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 500 AM AST (0900 UTC), the eye of Hurricane Sam was located
near latitude 21.5 North, longitude 59.1 West. Sam is moving toward
the northwest near 12 mph (19 km/h), and this general motion with 
an increase in forward speed is expected through tonight.  A turn 
toward the north is anticipated by late Friday, and a northeastward 
motion is forecast to begin on Saturday.  On the forecast track, 
the core of Sam will continue to pass well to the northeast of the 
northern Leeward Islands this morning, and pass to the east of 
Bermuda early Saturday.

Data from an Air Force Reserve Hurricane Hunter aircraft indicate 
that the maximum sustained winds are near 145 mph (230 km/h) with 
higher gusts.  Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale.  Some fluctuations in intensity are expected
during the next couple of days, but Sam is forecast to remain a
major hurricane through Saturday, with more significant weakening 
anticipated later in the weekend. 

Hurricane-force winds extend outward up to 60 miles (95 km) from the
center and tropical-storm-force winds extend outward up to 150 miles
(240 km).  NOAA buoy 41044 has recently measured a peak one-minute 
sustained wind of 78 mph (126 km/h) and a gust to 98 mph (158 
km/h). 

The latest minimum central pressure estimated from Air Force Reserve 
reconnaissance data is 937 mb (27.67 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC, 
and on the web at hurricanes.gov/graphics_at3.shtml?key_messages.

WIND:  Tropical storm conditions are possible on Bermuda beginning
Friday night or early Saturday.

SURF:  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.
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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

$$
Forecaster Brown
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