Category Five Hurricane Lee

[WxWatcher007]

3 minutes ago, Windspeed said:

Oh...

Only the beginning. Recon is in for a heck of a show this evening.

[MANDA]

40 minutes ago, Windspeed said:

Oh...

Lee is on his way to something special!

[friedmators]

How long does it take SSTs to recover after a hurricane pass?


.

[TheDreamTraveler]

Lee is finally popping off

 

 

[WxWatcher007]

Time for another deep dive.

Lee is entering its second period of rapid intensification, and the NHC in an extraordinarily rare move is now explicitly forecasting that Lee becomes a category five hurricane. This would be our eighth cat 5 since 2016--a remarkable period of high end tropical activity in the Atlantic basin. 

Rather than talk about intensity, I want to dedicate time to forecast track. 

If you recall from my post a few days ago, I broke down the different track stages for Lee. 

On 9/5/2023 at 10:03 AM, WxWatcher007 said:

Let's take a look at 95L, which will almost certainly be Tropical Storm Lee by the end of the day. The theme of this post will be managing expectations...

As @Windspeed's post showed, we started to see 95L really take a leap forward last night, and this morning it's basically a TC and the NHC is likely to start issuing advisories at 11am. 

 

That's about as good as you're going to get for a tropical wave in the MDR, a stark contrast from a lot of the slop and slow developing waves we've seen in recent years. 

A wider view shows just how far away this one is, and provides some clues to the landscape ahead. 

The first thing I notice here is concentrated convection around 95L. While there is drier air around, there's a solid pocket of moisture that's developing around the system. 

In addition, and this is important, there's very little shear. An upper level low to the north is too far north to inhibit development, and will probably do the opposite as an outflow channel gets established further west and an upper level anticyclone develops overhead. 

Intensity guidance is high end as a result. 

Some may look at this and say "Oh boy, a 5 is coming!". Not so fast my friend. This is almost certainly our next major hurricane, and I'd go as far as saying this is our next category four hurricane, our third of many thought in early August would be a quiet season. Once you get to these high end thresholds however, you have to watch for structural changes such as ERCs that could cap intensity. 

For intensity, the expectation should be a high end hurricane, but while it is possible, expecting a 5 is asking too much IMO. 

Now to why I'm actually writing this post.

The forecast track

If we're being honest with one another, everyone has their rooting interest. Whether you want a land threat, eye candy that stays out to sea, or just to be right with whatever it is you've already posted, we all see posts with bias. That's not necessarily a bad thing if you know how to sort through it. 

I'd hope that after all these years most of you see me as an objective poster with regard to tropical, but I'm often working to check my bias too.

Taking a step back, I think it's essential for everyone to remember how far out this system still is from having a well defined track evolution in the long range. 

I'm sure there are some reading that line and saying "well, that's what weenies always say". I agree. But I urge everyone to look past prior storms and analyze this current setup. 

 

Step I--WNW Movement Around Atlantic Ridge (High Confidence in 0-5 Days)
The current phase we're in is high confidence on the guidance and it makes sense in analyzing the steering environment. 95L is a relatively low rider currently, but as it moves westward it will intensify rapidly and will begin to gain latitude. This is a saving grace for the Antilles, as it should allow future Lee to travel WNW around an Atlantic ridge. Even accounting for the lack of an established low level center, this one should pass to the north of the Antilles. 

I am posting the op runs from 00z for comparison purposes because they are similar 5 days out. 

Step II--Turn Northward (Moderate Confidence in 6-9 Days)
I think there's high confidence that a turn occurs, but when and how sharp are open questions. On both the GFS and Euro, and by extension their ensembles, it's easy to see why a turn happens and why a turn itself is high confidence.

There's troughing in the E CONUS that provides a pathway for a northward turn. How far west future Lee can get before a turn may be very important to New England and especially Atlantic Canada. 

Once again, looking at the 00z operational GFS and Euro, you see the evolution. This first trough you see very early in the period allows for the turn, followed by a second and critical piece of troughing later in the 6-9 day period.

I'm inclined to trust the ensembles that show a turn between 65-70W, but this is something that is of lower confidence than the turn itself. This is where interests in Bermuda must watch closely. The degrees may matter if the next step gets tricky. 

Part III--The Final Turn (Low Confidence in 10+ Day Period)
This stage is the whole reason why I think it's far too early to lock in any land or OTS solutions. This is where you consider the probabilities rather than deterministic solutions. 

Recall the D6-9 GFS and Euro runs. The first trough is only enough to turn 95L north. It's not enough as currently modeled to sweep 95L out to sea as the models are trying to show a ridge attempting to build over the Maritimes/Atlantic.

That means that a second trough is required for a kick.

The problem is, while a Midwest trough is looking like it will try to dive in quickly after the first, it's unclear whether we see a positively tilted trough where the westerlies effectively kick 95L to the northeast and OTS, or a cutoff low that would effectively capture future Lee and pull it 1) northward into Atlantic Canada, or 2) northwestward into New England. 

Here are the ensembles at D10. This is a trend gif, showing the various solutions over the past two days at 240. Look at the ridging and troughing. The EPS has shown deeper eastern US troughing in recent runs with more ridging over the north Atlantic while the GEFS are kind of all over the place. Verbatim, it still may not be enough for a bona fide land threat outside of Bermuda, but there's enough uncertainty in the long range to pay attention along New England and Canadian Maritimes. 

Again, it's about keeping expectations in check. Long range consensus does not necessarily imply accuracy. We are going to need time to figure out what the steering pattern looks like after that northward turn occurs. A trend toward the coast can easily reverse at this range, and so can the current OTS solutions. 

If I were placing odds at this moment on what would happen it'd be the following: 

• 65% OTS--because it is extremely hard to trust a cutoff low being positioned and timed "perfectly" as 95L turns north to create a land threat.
• 20% Atlantic Canada Threat--because an extended northward track with a slight bend (a la Fiona) is more likely with any kind of cutoff or negatively tilted trough. 
• 15% New England Threat--because the turn north is more likely to happen east of the region and a threat would require the aforementioned positioning and timing to be precise for what'd likely be some type of extended NNW to NW heading.

These numbers will change, but the overall message in this very long analysis is that while we have higher confidence in the 0-5 and perhaps even higher confidence in some aspects of the 6-9 day period, there is a lot that needs to be sorted out given the steering pattern potential beyond ~day 8. 

Substantively, there hasn't been a lot of change in my thinking. Lee is a threat to land, but the signal for a landfall while increasing, remains highly uncertain, especially at this range. 

Stage I--WNW Movement Around Atlantic Ridge
This was high confidence, and it's happening as I type. The current NHC heading for Lee is WNW at 15mph from 16.4°N 50.0°W. This is important to the rest of the forecast. The image is small, but it's critical to pay attention to the western component of Lee in a few days. 

The current forecast, which is high confidence still, takes Lee on a WNW heading north of the Antilles. However, in approximately 5-6 days, we should start seeing a turn northward as the ridge is weakened. 

 

Stage II--Turn Northward
The northward turn is going to happen, but how far west does Lee get before that turn is made? Currently, the guidance has that turn happening between 65-70W. In the last few days, the trend has been more southwest with Lee, and those degrees matter for the turn, because the guidance has had less of a sharp recurve and more of an extended northward heading once Lee turns. 

I think this is where recon will be vital. As recon samples the environment around Lee, it should be able to give the guidance essential information on whether the currently forecasted weakening of the ridge is accurate, or whether the weakening is over/understated. 

This is happening as confidence increases that a trough will develop over the E CONUS and a ridge over the Maritimes/Atlantic attempts to rebuild as Lee turns north. The 00z ensemble runs below look at the steering pattern from 144-240.

You will notice a new wrinkle in these runs--TD 14, which is soon to become Margot. The spacing between Lee and future Margot is important as Margot may prevent the Atlantic ridge from amplifying more than it otherwise would. The greater spacing the greater the chance the ridge truly flexes, pushing Lee on some type of bended heading (NNW most likely) toward land. Every degree of longitude will matter. 

Stage III--The Final Turn
Here's where the E CONUS trough comes in. It's still unclear what kind of orientation and depth it'll have. Should it become pinched off into a cutoff low, you can expect it to "capture" Lee and bring some type of land impact depending on where that capture occurs. If it is shallow and progressive, it should create just enough of a weakness in the ridge to give Lee a last minute kick. 

In my opinion, this is still highly uncertain, but I lean toward the fact that Lee is likely turning between 65-70W, the presence of future Margot preventing too much Atlantic ridge amplification, and the fact that guidance continues to suggest on balance that the E CONUS trough is more kicker than anything else to keep the OTS solution slightly favored at this time.

This could certainly change, however, and I will note that the European model and ensembles have become more bullish on land impacts given a more favorable ridge/trough alignment for a northward turn that doesn't materialize into a steeper ENE recurve like the GFS. 

While the differences are small among the ensembles in an absolute sense, they lead to very different sensible wx outcomes. 

As a result, I have higher landfall odds than I did a few days ago. While they are much higher than what I think the climatological average would be, they are still fairly low in the whole scheme of things. It's still pretty early IMO to discern with a high degree of confidence what happens in Stage III, other than I still believe most of the East Coast of the US is not facing a legitimate threat from Lee. This is New England or Atlantic Canada IMO.  

55% OTS--because of the high confidence that a turn happens between 65-70W, outside of standard climatology zone for a northeast US landfall, the presence of future Margot impacting the Atlantic ridge, and because it is extremely hard to trust a E CONUS cutoff low being positioned and timed "perfectly".

25% Atlantic Canada Threat--because a turn north between 65-70W still puts Nova Scotia in particular in the direct path of Lee should an extended northward heading materialize. Even a last second turn ENE could allow for muted impacts or a direct hit of Newfoundland.  

20% New England Threat--because while my odds are higher than the ensembles would show currently, I still think there's room for the ridge/trough alignment to become more favorable for a westward shift of guidance, leading to a glancing blow. A direct hit in SNE would be less favored at this time. 

I take no stance right now on intensity should Lee become a land threat, other than it would certainly be far weaker than its peak at that time because of cooler SSTs, lower OHC, and potential extratropical transition. 

[stormwatcherJ]

Great summary above! So you think no chance for NC's OBX? 

[NJsnow89]

4 minutes ago, stormwatcherJ said:

Great summary above! So you think no chance for NC's OBX? 

Zero chance bud. 

[GaWx]

9 hours ago, GaWx said:

The 0Z EPS' 6 (12%) CONUS hits is the highest yet, beating the 5 hits by the 0Z of 24 hours ago and that was for that full 15 day run. Four hit ME and two hit MA. And that's only through 240 as it appears a couple more will likely hit after 240.

 This is more evidence that the NE is not safe even though I still consider it a low chance. 
 
 Nova Scotia and the area near Bermuda appear to get hit the hardest.

 As mentioned, the 0Z EPS had 6 members with US hits (4 ME and 2 MA) just through 240, which was already the largest # of hits of any complete EPS run yet, and with the post 240 portion still not then out. 

 The post 240 portion showed another 4 hits (3 MA and 1 ME meaning a total of 5 ME and 5 MA) for a full 0Z EPS total of 10 (20%), which doubles the previous run highest hit total of 5 (10%) that was from the run 24 hours earlier.

 Summary of EPS (0Z and 12Z) runs' CONUS hits:

0Z 9/7: 10 (20%) (9/15-18) (5 ME, 5 MA)
12Z 9/6: 3 (6%) (ME 9/15 & 9/17, MA 9/18)
0Z 9/6: 5 (10%)
12Z 9/5: 2 (4%)
0Z 9/5: 4 (8%)                                             
12Z 9/4: 1 (2%)            
0Z 9/4: 2 (4%)

[WxWatcher007]

9 minutes ago, stormwatcherJ said:

Great summary above! So you think no chance for NC's OBX? 

Right. Obviously plenty of wave activity and possible beach erosion, but this turns north well east of the east coast. The only reason why this thread is active is because there's enough of a signal for a ridge to block a quick escape OTS as a trough pulls it north.  

[jconsor]

Combination of stronger ridge nosing down to NW of Lee and upper low to its NE trending stronger and a little closer to Lee is likely the reason we are seeing more ensemble members trend toward a bend to nearly due west between 60-70W longitude.

 

[WxWatcher007]

2 minutes ago, jconsor said:

Combination of stronger ridge nosing down to NW of Lee and upper low to its NE trending stronger and a little closer to Lee is likely the reason we are seeing more ensemble members trend toward a bend to nearly due west between 60-70W longitude.

 

That's where I think recon would be very helpful. Just in general I'm always wary of models underplaying the strength of ridging, and that has been an issue this summer.

Here, it matters because as you know the further west this goest the more threatening this becomes to someone if that trough continues to trend towards more amplified. 

[SchaumburgStormer]

Going straight Hulk mode today.

 

[nycsnow]

 

[NorthHillsWx]

4 hours ago, NorthHillsWx said:

Yep. This storm is going to be an absolute beaut with a pretty eye too. By tomorrow morning (maybe earlier) I expect cat 4

Lee may reach cat 4 by 5 pm. This thing is absolutely going off at the moment 

[MANDA]

4 minutes ago, SchaumburgStormer said:

Going straight Hulk mode today.

 

Just amazing!  Wish recon could of been in there from earlier this morning.  Would have loved to see actual pressure and wind data.  I think though that it is just coming into travel range....about 50W is when they usually begin recon.

[NJwx85]

14 minutes ago, nycsnow said:

 

Nearly 200mph max winds if it verified. 

[thunderbolt]

13 minutes ago, NorthHillsWx said:

Lee may reach cat 4 by 5 pm. This thing is absolutely going off at the moment 

Check out the lightning wrapping around it you know it’s balls to the wall now baby

[NeffsvilleWx]

Going to be a bumpy ride for recon. Hopefully they don’t end up in a Hugo situation — which occurred during a period of RI.

[JonClaw]

3 minutes ago, NJwx85 said:

Nearly 200mph max winds if it verified. 

Note that the all-time Atlantic record is currently held by Hurricane Allen (1980) at 190 MPH

[marsman]

4 minutes ago, NeffsvilleWx said:

Going to be a bumpy ride for recon. Hopefully they don’t end up in a Hugo situation — which occurred during a period of RI.

Recon is airborne.

[WxWatcher007]

10 minutes ago, marsman said:

Recon is airborne.

I think that one is to sample the environment?

[GaWx]

12Z Euro 144 a whopping 41 mb weaker (960) than 0Z 156 (919) and barely ESE of the 0Z

[NeffsvilleWx]

Recon is back on the ground per ADSB data. Wonder what happened.

[MANDA]

5 minutes ago, NeffsvilleWx said:

Recon is back on the ground per ADSB data. Wonder what happened.

They looked at the latest satellite and said "hell no" 

[MJO812]

14 minutes ago, GaWx said:

12Z Euro 144 a whopping 41 mb weaker (960) than 0Z 156 (919) and barely ESE of the 0Z

Maine hit

[NJwx85]

12z HAFS-A. If true, Lee will probably peak in intensity on Saturday or Sunday.

Check out how much the wind field increases from now until the end of the run.

[GaWx]

7 minutes ago, MJO812 said:

Maine hit

Indeed, E ME 966 mb on 9/16 at 18Z

[MANDA]

Nice dual outflow channels with northern one evacuating into an atmospheric sink.

[Amped]

Seems Idiala had a much harder time clearing out the eye. 

[MANDA]

1 minute ago, NJwx85 said:

12z HAFS-A. If true, Lee will probably peak in intensity on Saturday or Sunday.

Check out how much the wind field increases from now until the end of the run.

It has to weaken, you are not going to keep this pristine environment that long.  Will be a huge wave and swell producer for east coast and Atlantic Canada but this is not going to hang onto cat 4 / 5 status once north of the Islands.  The environment and overall pattern does degrade.