ATL: SAM - Remnants - Discussion

[ElectricStorm]

Hurricane Sam Intermediate Advisory Number 36A
NWS National Hurricane Center Miami FL AL182021
200 PM AST Fri Oct 01 2021

...AIR FORCE HURRICANE HUNTERS INDICATE THAT SAM IS MAINTAINING
CATEGORY 4 STRENGTH...
...CORE OF THE HURRICANE EXPECTED TO PASS WELL EAST OF BERMUDA
TONIGHT...


SUMMARY OF 200 PM AST...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...29.1N 61.9W
ABOUT 280 MI...450 KM SE OF BERMUDA
MAXIMUM SUSTAINED WINDS...150 MPH...240 KM/H
PRESENT MOVEMENT...N OR 355 DEGREES AT 21 MPH...33 KM/H
MINIMUM CENTRAL PRESSURE...937 MB...27.67 INCHES

[Owasso]

150mph/937mb for the 2PM Intermediate.

[Hypercane_Kyle]

NHC sticking with 130 knots.

It's going to take truly overwhelming evidence for Sam to be considered for an upgrade, especially as question marks exist regarding flight level winds mixing to the surface.

Code: Select all

2:00 PM AST Fri Oct 1
Location: 29.1°N 61.9°W
Moving: N at 21 mph
Min pressure: 937 mb
Max sustained: 150 mph

[NotoSans]

Intermediate advisory keeps it at 130kt.

[Ubuntwo]

152kt FL and 110kt SFMR (115 flagged). Subpar mixing right now but impressive winds aloft.

Really, really doubt that’s the case. Dropsonde in ne eyewall showed efficient mixing to the surface, and sfmr was lower in the NE than the SW. I have a hard time believing a 72% reduction when measurements in the SW quad and NE dropsonde suggest it’s above 90%

Sam is a symmetric storm at surface and has cat 4 winds in almost every quadrant. At flight level Sam is less symmetric and that eastern side is getting a boost from forward speed. Does not look like baroclinic influence but all things considered this is a little below the 135kt storm FL reduction would imply. If convection deepens overnight Sam could get there.

[grapealcoholic]

Never forget.

[HurricaneEnzo]

I think 125kts-130kts was the right call. No compelling evidence it is any stronger. Still a beast of a storm for this part of the world.

[NotoSans]

Noooo recon dropped the dropsonde too early! They didn't drop it around peak winds!

However, the dropsonde does show a conversion rate of 132/142 = 93% of winds mixing down to the surface, which would give 152*93% = 141 kt for the peak winds. I think the dropsonde does an excellent job at confirming that winds are mixing down very well and that there's just something wrong with SFMR right now.

Don’t think it is appropriate to use a single dropsonde profile to determine if surface winds are mixing effectively down to the surface. A mean vertical wind profile, cross checked with SFMR data, may be a better approach.

Surface winds measured by dropsondes are representative of gusts, unlike SFMR which measures at a longer interval. A single dropsonde may hit mesoscale features as it drops and rotates around the eyewall, which inflate the winds measured at the lower levels.

In fact, if we use the lowest 150m winds and apply the standard conversion factor of 0.85, that dropsonde alone only supports an intensity of 115kt.

NHC’s 130kt is a good compromise based on the available data IMO.

[aspen]

I would’ve gone with 135 kt due to the increase in FL winds and the slight deepening between passes. If Sam is being enhanced by the trough, this could keep it as a major even longer before shear and marginal SSTs finally take a toll.

If recon were to check the NE eyewall again, we could get all the data needed to justify or refute an upgrade, but they’ll probably leave now.

[Hypercane_Kyle]

Recon is done. Ascending and heading out.

[aspen]

Once again, Sam is one of the best looking storms that could be a Cat 5 but isn’t officially a Cat 5. I really hope it’s able to maintain itself until the next recon flight arrives, but it’ll be moving into cooler waters soon.

[Teban54]

Finally able to check again after a loooong flight, and Sam certainly lived up to my expectations. This is giving me Lorenzo vibes.

Hope Sam is able to mix down the winds more effectively while we wait for the next recon (or at least SFMR won't have any issues), so that we can get some more convincing evidence of whether this is or isn't a Cat 5.

Edit: Sam now has on-and-off cool convection after I posted this (cool according to Sam standards). Maybe that will do it? Idk.

[floridasun]

soon we wont have recon because getting far for them fly out

[AlphaToOmega]

155100 2842N 06140W 6977 02747 9627 +085 +026 150147 152 109 011 00

152-kt unflagged FL reading
152 kts * 0.9 = 136.8 kts
This supports 135 knots

[Craters]

In case you haven't seen it yet (a search for "Saildrone" in this thread didn't come up with anything), here's a very interesting perspective on the conditions in the eye of Sam:

https://www.noaa.gov/news-release/world-first-ocean-drone-captures-video-from-inside-hurricane

There's a video a little way down from the top.

[Yellow Evan]

155100 2842N 06140W 6977 02747 9627 +085 +026 150147 152 109 011 00

152-kt unflagged FL reading
152 kts * 0.9 = 136.8 kts
This supports 135 knots

SFMR’s are much lower despite their high bias. 130 knots is probably fair.

[tolakram]

 https://twitter.com/BMcNoldy/status/1444012121629413378

[tolakram]

 https://twitter.com/RyanRickert4/status/1443960893801381893

[Hypercane_Kyle]

By all accounts, Sam has been one of the most impressive Cape Verde systems I've ever tracked.

[Fancy1001]

It’s sad that we’ll never likely know whether or not Sam made it to category five during it’s first or second peak