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14-09-2020, 22:05   #196
pad199207
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Sally now a Cat 2
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14-09-2020, 22:59   #197
Gaoth Laidir
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That oil platform KVOA actually has an anemometer height of 160 metres above the sea surface, which is why reported a peak 8-minute wind of 87 knots (converting to a 1-minute mean of around 96 knots) and a gust of 102 knots as the northwestern eyewall passed through. At the standard 10 metres height the 96 knots would reduce to around 77 knots.

Buoy 42040, 30 miles to the west, has reported peak 8-minute of 39 knots (44 knots 1-minute).

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14-09-2020, 23:30   #198
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The latest satcon intensity estimate shows what I was saying earlier about the difference frequent aircraft recon data have on official intensity fixes. The classical satellite estimates are all shown in various colours while the official NHC best track estimate is in grey. The NHC have gone way above all of the satcon estimates today as recon data have come in. Without these the official intensity would have been more like somewhere around 60 knots. This has happened on several other occasions too, which calls into question the validity of comparing rapid intensity trends of recent years, when recon aircraft have become like bees around a hive. How many historical storms have had similar real intensities and not had them measured by aircraft?

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15-09-2020, 11:44   #199
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Sally has weakened overnight and aircraft data haven't found any surface winds above 58 knots, nor have there been surface buoy or platform winds that high, yet the NHC continue to give it an intensity of 75 knots. I sometimes struggle to understand their logic.

Quote:
Hurricane Sally Discussion Number 16...Corrected
NWS National Hurricane Center Miami FL AL192020
400 AM CDT Tue Sep 15 2020

Corrected Key Messages 2 and 3

There has been little change overall in Sally's convective
structure in both satellite and Doppler radar data. An eye has tried
to close off several times this morning, but after less than 30
minutes the southern eyewall has eroded. Until just recently, the
central pressure had been steady for the past several hours at 986
mb. However, the most recent Air Force Reserve reconnaissance pass
through Sally's center reported a dropsonde pressure of 984 mb and
13 kt winds, which equals a pressure of 983 mb. Maximum 700-mb
flight-level winds observed have only been 63 kt and peak SFMR
winds have been 58 kt. Also, reports from nearby oil rigs have
dropped off significantly since yesterday are are now in the 40-50
kt range. Based on these data, the initial intensity has been
lowered to 75 kt.

The initial motion estimate to 300/02 kt. After a brief jog due
west, it appears that Sally has resumed a slow drift toward the
west-northwest. Sally is embedded within weak steering flow based
on 0000Z upper-air data indicating 500-mb heights of 5900 meters
and slightly higher surrounding the cyclone from Florida northward
into the Tennessee Valley and then westward into the central and
southern Plains. This weak steering pattern is expected to persist
for the next few days, with a weak mid-level trough forecast to
move into the Missouri and Tennessee Valleys by Wednesday and
Thursday, which will gradually lift Sally northward and then
northeastward. Sally is forecast to merge with a frontal system by
day 4 or 5. The new NHC forecast track is similar to the previous
advisory and lies down the middle of the rather divergent model
guidance envelope.

Sally is now expected to remain in a moderate to high mid-to
upper-level wind shear environment. Ina addition, some modest
upwelling is likely occurring in the inner-core region based a SST
decrease of nearly 2 deg F during the past 24 hours based on data
from buoy 42012. After the Sally makes landfall, rapid weakening is
forecast and Sally should become post-tropical in 3 days or less.

Users are reminded to not focus on the exact forecast track or the
specific timing and location of landfall. Hurricane-force winds,
dangerous storm surge, and flooding rainfall will affect a large
portion of the north-central Gulf Coast during the next few days.

KEY MESSAGES:

1. It is still too early to determine where Sally's center will move
onshore given the uncertainty in the timing and location of Sally's
northward turn near the central Gulf Coast. Users should not focus
on the details of the official forecast track, since NHC's average
forecast error at 36 hours is around 60 miles, and dangerous storm
surge, rainfall, and wind hazards will extend well away from the
center.

2. An extremely dangerous and life-threatening storm surge is
expected for areas outside the southeastern Louisiana Hurricane and
Storm Damage Risk Reduction System from the Mouth of the Mississippi
River to the Okaloosa/Walton County Line in the Florida Panhandle,
where a Storm Surge Warning is in effect. Residents in these areas
should follow any advice given by local officials.

3. Hurricane conditions are expected today within the Hurricane
Warning area along the Mississippi and Alabama coastlines and the
western Florida Panhandle. Tropical storm conditions are already
occurring in some of these areas.

4. Historic flooding is possible with extreme life-threatening flash
flooding likely through Wednesday along and just inland of the
central Gulf Coast from the western Florida Panhandle to far
southeastern Mississippi. Widespread moderate to major flooding on
area rivers is forecast along and just inland of the central Gulf
Coast. Significant flash and urban flooding, as well as widespread
minor to moderate river flooding is likely across inland portions of
Mississippi, Alabama, northern Georgia, and the western Carolinas
through the week.


FORECAST POSITIONS AND MAX WINDS

INIT 15/0900Z 28.9N 88.1W 75 KT 85 MPH
12H 15/1800Z 29.2N 88.4W 75 KT 85 MPH
24H 16/0600Z 29.9N 88.5W 75 KT 85 MPH
36H 16/1800Z 30.6N 88.3W 60 KT 70 MPH...INLAND
48H 17/0600Z 31.4N 87.5W 35 KT 40 MPH...INLAND
60H 17/1800Z 32.2N 86.2W 25 KT 30 MPH...INLAND
72H 18/0600Z 32.8N 84.6W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 19/0600Z 33.2N 81.3W 20 KT 25 MPH...POST-TROP/EXTRATROP
120H 20/0600Z...DISSIPATED


I like the subtle pun in the discussion on TS Teddy, which is forecast to become a Cat 3 later on.

Quote:
....
Teddy bears watching in the long range for
category 4 strength, but regardless of the details, all of the
guidance show it becoming a classical large and powerful September
hurricane.
...

Last edited by Gaoth Laidir; 15-09-2020 at 11:48.
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15-09-2020, 22:52   #200
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Teddy bears down on Bermuda would make a good headline (earlier on it was supposed to miss by a small margin to the east, the 00z GFS takes it right over top of Bermuda).

Looked earlier like neither Paulette nor Sally would have any time as a major so the count remains 20/7/1 until Teddy boosts it to 20/8/1 or 20/8/2 perhaps tonight or tomorrow. (added later _ Sally moving at a snail's pace towards landfall has intensified more than predicted and is a borderline cat-3 storm now, advisory not out yet but 110 mph winds detected) ... Vicky does not seem to have much of a future either (although she stubbornly clings to 50 mph intensity).

So really if the season were to be at 13/8/1 or 2 it would seem rather anemic, and there have been at least seven weak tropical storms, so ... it continues to underwhelm somewhat.

Just as with 2005, it's female named storms that are the stronger of the two.

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16-09-2020, 10:08   #201
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Check out the Medicane off the coast of Greece.

https://earth.nullschool.net/#curren...c=4.004,33.009

Going to strengthen as well into a powerful tropical like storm and hit Greece.
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17-09-2020, 22:22   #202
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Teddy intensified to 120 knots (Cat 4) this evening due to a combination of low shear and water temperatures of around 28.5 degrees, heat content around 55 kJ/cm². It is the second major hurricane of the season. It could strengthen slightly more overnight before levelling off and then slowly decreasing as mid levels dry out slightly and heat content reduces around the upwelled wake of Paulette. It could come close to Bermuda Sunday/Monday, but at that stage it's looking more like Cat 2/1.



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17-09-2020, 22:42   #203
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A good eyewall has formed around most of the centre. Finally a proper Atlantic hurricane this season.

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17-09-2020, 23:15   #204
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Quote:
Originally Posted by Gaoth Laidir View Post
A good eyewall has formed around most of the centre. Finally a proper Atlantic hurricane this season.
Laura wasn't a proper Hurricane when it destroyed a decent chunk of Louisiana?
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18-09-2020, 06:57   #205
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Quote:
Originally Posted by sdanseo View Post
Laura wasn't a proper Hurricane when it destroyed a decent chunk of Louisiana?
I mean it's a proper major hurricane from the MDR that's slowly developed in the traditional way and will last for a decent amount of time. Laura was of course major too but it was a bit more messy on satellite most of the time.
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18-09-2020, 16:21   #206
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Tropical Storm Wilfred has developed in the MDR and is by 3 weeks the earliest 21st-named Atlantic storm on record. Like many others, though, it will not amount to much, reaching only 40 knots over the next couple of days before dissipating in mid-Atlantic within 5 days.

Tropical Depression 22 formed in the SW Gulf of Mexico overnight and may or may not get up to near hurricane strength near the Mexico or Texas coast in 3 days or so. Note this from the latest discussion on it.

Quote:
It should be noted that the Air Force Reserve Hurricane Hunter aircraft that was scheduled to investigate the depression had to turn back after getting hit by lightning.
Meanwhile, Teddy is going strong at 115 knots and should hold that for a little while longer before a gradual weakening phase occurs before hitting Nova Scotia as an extra-tropical storm.

12Z SHIPS



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18-09-2020, 17:44   #207
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Now they have slapped the name Alpha on the low approaching Portugal. That seems a bit over the top, it's a low.

Anyway, this means no Hurricane Alpha again in 2020 and probably Hurricane Beta again (the GOM thing about to get a name).

I just think they are pulling out all the stops to get to Mu and Nu which should excite comedians as much as climatologists.
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18-09-2020, 18:02   #208
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That seems a bit ridiculous alright. The very first advisory is for it to dissipate within a day or so.
I get that it technically meets the criteria, but you'd have to think they regularly ignore lows like this so far NE.
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18-09-2020, 20:37   #209
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It all helps beef up the stats, the same way they sometimes give intensities higher than any of the available data suggest. Alpha was just a normal extratropical low that's been moving southwards during the week and happened to develop convection, hence it's classified a sub-tropical low. No tropical origins whatsoever. Still, Ryan Maue will be on Twitter with more exaggerated statements on it. It's already made landfall in mid-Portugal.

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18-09-2020, 21:10   #210
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UKMO FAX analysis at 18Z.

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