Category Five Hurricane Lee

[wthrmn654]

1 hour ago, bluewave said:

It’s funny how the OP Euro and machine learning models were both showing landfalls in SE New England in earlier runs before correcting further east toward the consensus. As to why this was the case, we can leave to the modelers writing the code. It may come down to the OP Euro being over amped at times for some reason. But this bias at times can work like in Sandy when the pattern was super amped up. So I guess some storms play to certain model biases depending on the situation. If they could train the AI to learn how and which biases to correct on a situational basis, then they will really have something.

https://www.ecmwf.int/en/about/media-centre/news/2023/how-ai-models-are-transforming-weather-forecasting-showcase-data

In a recent ECMWF blog and a Newsletter article, we’ve been highlighting the rapid rise of data-driven forecasts. These are produced by machine-learning-based forecasting models, created by innovators such as NVIDIA, Huawei and Google DeepMind.

The ERA5 reanalysis, produced by the EU-funded Copernicus Climate Change Service (C3S) implemented by ECMWF, is the dataset used to train these models. They can make accurate 10-day forecasts when provided with good initial conditions.

This summer, we focused on analysing Huawei’s Pangu-Weather to understand its strengths and weaknesses, with results collated in a submitted manuscript. At this early stage in the technology, some results are already displaying comparable skill to ECMWF’s Integrated Forecasting System (IFS), which is an exciting achievement.

Gfs in the super long range also had been showing a direct hit in the north east while the euro at its longest range was more east orginally. 

[GaWx]

11 hours ago, bluewave said:

The GFS did the best with the track of Lee.  Maybe this was just the GFS right of track bias at work. Like the old broken clock is right twice a day metaphor.

 

 

 Despite the noted tendency for the GFS to be too far right with recurving TCs, it was interestingly enough way too far LEFT with both of the 2022 Ian SE US landfalls and also too far left with last month's Idalia FL landfall. Thus I'm wondering if the GFS really still has a too far right bias for recurves and instead now has a net neutral or possibly even a left bias:

1. FL Ian landfall 1-4 days out:

- GFS was still way up at Apalachee Bay just 68 hours from landfall (0Z 9/26 run) vs the actual Port Charlotte (PC) landfall point. That's a 200 mile error to the left at just 68 hours out!

- At that point, UKMET was dead-on at PC and ICON was at Venice, only 25 miles from PC.

- GFS wasn't close to PC until the 12Z 9/27 run, just 32 hours out. Until then it was too far left on all runs out going back at least several days:

2. SC Ian landfall 1-4 days out:

- GFS was still way down at Hilton Head just 54 hours from landfall (12Z 9/28 run). That's 100 miles to the left of the actual track.

- GFS wasn't close to the actual landfall location of Georgetown until the 12Z 9/29 run, just 30 hours out. Until then it was too far left on all runs out going back at least several days:

3. FL Idalia landfall:

- GFS was on the left side of the model consensus for several days of runs before landfall and about as far left as any

- Just 30 hours out with the 8/29 6Z run, the GFS was still 50 miles too far left of the actual landfall

- The Euro and ICON were almost always to the right of the GFS (as well as much closer to the actual track), and the UKMET was usually to the right of the GFS.

[NorthHillsWx]

Recon matches what we all saw on satellite: Lee is losing tropical characteristics quickly. More or less the temp profile of a front and the highest winds are well away from the center. That NW band actually has the first hurricane-force SFMR values seen in the last couple flights 

[mob1]

There must be some sting jet on the southern end of the transitioning Lee as recon just reported multiple unflagged SFMR readings of 82 knots. 

[NorthHillsWx]

4 minutes ago, mob1 said:

There must be some sting jet on the southern end of the transitioning Lee as recon just reported multiple unflagged SFMR readings of 82 knots. 

Exactly. Models nailed this. 80+ kts and no rain. That’s definitely the non tropical sting jet

[bluewave]

4 hours ago, GaWx said:

 Despite the noted tendency for the GFS to be too far right with recurving TCs, it was interestingly enough way too far LEFT with both of the 2022 Ian SE US landfalls and also too far left with last month's Idalia FL landfall. Thus I'm wondering if the GFS really still has a too far right bias for recurves and instead now has a net neutral or possibly even a left bias:

1. FL Ian landfall 1-4 days out:

- GFS was still way up at Apalachee Bay just 68 hours from landfall (0Z 9/26 run) vs the actual Port Charlotte (PC) landfall point. That's a 200 mile error to the left at just 68 hours out!

- At that point, UKMET was dead-on at PC and ICON was at Venice, only 25 miles from PC.

- GFS wasn't close to PC until the 12Z 9/27 run, just 32 hours out. Until then it was too far left on all runs out going back at least several days:

2. SC Ian landfall 1-4 days out:

- GFS was still way down at Hilton Head just 54 hours from landfall (12Z 9/28 run). That's 100 miles to the left of the actual track.

- GFS wasn't close to the actual landfall location of Georgetown until the 12Z 9/29 run, just 30 hours out. Until then it was too far left on all runs out going back at least several days:

3. FL Idalia landfall:

- GFS was on the left side of the model consensus for several days of runs before landfall and about as far left as any

- Just 18 hours out with the 8/29 6Z run, the GFS was still 50 miles too far left of the actual landfall

- The Euro and ICON were almost always to the right of the GFS (as well as much closer to the actual track), and the UKMET was usually to the right of the GFS.

The most egregious left of track bias with the GFS was with Joaquin while the Euro was consistently OTS and correct. The one truism is that while the GFS tends to have some right of track bias, it’s usually wrong when it’s the furthest west. This works with both snowstorms and hurricanes.

 

https://www.washingtonpost.com/news/capital-weather-gang/wp/2015/10/06/what-the-european-model-win-over-the-american-model-means-for-weather-forecasting/

[Floydbuster]

 

[KPITSnow]

Interestingly it doesn’t look like the right turn into Nova Scotia has started yet and if anything still looks like there is a north west component to it. Maybe it splits NB and NS and turns right into the bay of fundy.

 

regardless I enjoy tracking these storms going into less that usual Locations just like Hilary in CA 

[Downeaster1]

Just breezy here in Auburn, ME.  Spitting rain about 20 mins ago.  A few very small oak branch ends down.  ! three foot long white pine branch, maybe an inch in diameter down.  Trees are fully leafed and haven't started changing color at all.  Barometer bouncing around in the 29.55 range.

[Chinook]

Here are current observations. 43 knots gusting to 53 knots at Lunenberg Nova Scotia, gust to 58 knot at Halifax

 

[Chinook]

gusting to 49 knot at Mitinicus Island Maine (part of the buoy system, CMAN observation)

 

[KPITSnow]

This looks like it may landfall right on the border. Still no real eastward motion 

[Chinook]

976 mb

[Chinook]

974.2 mb at Yarmouth Nova Scotia, so probably bottoming out what that airport will measure.

[marsman]

Been watching Mount Washington's weather, might be the most interesting thing going on. Currently showing winds at 72mph, gusts to 82 and 38F. Clouds are ripping across the summit.

[Chinook]

wind gusts to 61mph (53 kt)

[GaWx]

4 hours ago, KPITSnow said:

This looks like it may landfall right on the border. Still no real eastward motion 

For the record per NHC, the core moved over far W NS and center is now over Bay of Fundy. So, officially no US center landfall in case anyone is wondering:

Post-Tropical Cyclone Lee Discussion Number 46
NWS National Hurricane Center Miami FL AL132023
500 PM AST Sat Sep 16 2023

The core of Lee briefly moved across Long Island in Western Nova 
Scotia within the past hour or so. Satellite images and surface 
observations indicate that the center is now over the Bay of Fundy. 
Rain bands continue to spread across portions of Maine, New 
Brunswick, and Nova Scotia as seen in radar images. A pair of ASCAT 
passes from several ago showed that Lee remains very large, but the 
core winds have decreased below hurricane-force. Considering some 
undersampling of that data, the initial intensity was lowered to 60 
kt on the 1800 UTC intermediate advisory.

The forward motion of Lee is slower than earlier today as it 
moves near the west coast of Nova Scotia. However, the storm is 
expected to turn northeastward and accelerate late tonight and 
Sunday, bringing the system across the Canadian Maritimes. Little 
change was made to the previous NHC track forecast.

FORECAST POSITIONS AND MAX WINDS

INIT 16/2100Z 44.5N 66.1W 60 KT 70 MPH...POST-TROPICAL
12H 17/0600Z 46.5N 64.5W 50 KT 60 MPH...POST-TROP/EXTRATROP

[GaWx]

[Chinook]

It would appear that the low is at the mouth of the Bay of Fundy

[Chinook]

Did you know? January 5, 2018 had a lower pressure at the same spot at TS Lee right now. It was a blizzard with 949mb at the mouth of the Bay of Fundy, January 5, 2018, 03z. Also, February 8, 2020, 00z had 966mb with rain/snow.

how about 968mb with rain/snow in April?

 

 

non-occluded low at 976mb last year, March

 

[Chinook]

lowest pressures in the fall season, Bar Harbor. Sep 15-16 2009 is not correct data, as the pressure was about 1010mb.

 

[Chinook]

Houlton all time pressure records (not sure if any of these are in error)

 

[GaWx]

 The SSTa image below from Sep 13th shows that significant cooling of the upper ocean resulting from slow moving large and major H Lee stirring up the waters started well before center passage. Note that at 11AM EDT on Sep 13th Lee was still down at 26.4N, 67.2W, despite a new blue area that stretches as far NW as 29N, 69W, that was yellow the prior day. So, the SST had already cooled ~1F all the way up at 29N, 69W, vs 24 hours earlier even though the center was still over 200 miles to the SE at the end of that 24 hours. The center didn’t even get near 29N, 69W, for another ~18 hours, during which that area and nearby cooled more. During the analyzed period, Lee was moving under 10 mph and getting larger. I was educatedly guessing that Lee’s slow movement combined with large size was helping to keep its strength in check by causing SST cooling well ahead of the center. I assume that a little cooling well ahead of a center would be normal but this appears to have been more than average cooling due to a combo of slow movement and large size:

[NorthHillsWx]

Lee, Franklin, Idalia, and climo have laid down a protective barrier for the east coast for anything coming from the east the rest of this season.