Category Five Hurricane Lee

[TPAwx]

Fantastic synoptic set-up to keep this monster away from a direct US impact.

Love it!!

[Windspeed]

At any rate, it would be easy to get comfortable on the higher probability of OTS with ensembles screaming it. But as is reiterated, we're still well beyond 5 days. Modeling has improved since 2017, but even ensembles swing and miss on MDR systems outside of that window. Just keep in mind that the evolution of the WAR and an ECONUS trough is still not in stone, even if swing back to a rebuilding ridge or cutoff in the eastern interior is trending unlikely. This ensemble from Irma is a reminder that even a strong hurricane may not go polar as fast as initially modeled. We don't even have a TC yet.

[Floydbuster]

10 minutes ago, Windspeed said:

At any rate, it would be easy to get comfortable on the higher probability of OTS with ensembles screaming it. But as is reiterated, we're still well beyond 5 days. Modeling has improved since 2017, but even ensembles swing and miss on MDR systems outside of that window. Just keep in mind that the evolution of the WAR and an ECONUS trough is still not in stone, even if swing back to a rebuilding ridge or cutoff in the eastern interior is trending unlikely. This ensemble from Irma is a reminder that even a strong hurricane may not go polar as fast as initially modeled. We don't even have a TC yet.

Wow did the ensembles really have Irma that far north? I didn't remember that at all.

[Prismshine Productions]

Wow did the ensembles really have Irma that far north? I didn't remember that at all.

Yep, they did, just like Florence was supposed to have recurved before Bermuda (look what happened)

Sent from my SM-S146VL using Tapatalk

[GaWx]

9 minutes ago, Windspeed said:

At any rate, it would be easy to get comfortable on the higher probability of OTS with ensembles screaming it. But as is reiterated, we're still well beyond 5 days. Modeling has improved since 2017, but even ensembles swing and miss on MDR systems outside of that window. Just keep in mind that the evolution of the WAR and an ECONUS trough is still not in stone, even if swing back to a rebuilding ridge or cutoff in the eastern interior is trending unlikely. This ensemble from Irma is a reminder that even a strong hurricane may not go polar as fast as initially modeled. We don't even have a TC yet.

Good point. I'm currently near 75% for a miss of the CONUS or pretty near the climo based chance for it to not hit. If I were to go strictly by the EPS, I'd be near 95%. But in deference to some of the other models and the extra uncertainty present before a TC has even formed, I'm not nearly that high at least for the time being.

[Windspeed]

Wow did the ensembles really have Irma that far north? I didn't remember that at all.

Yes, at one point they did. Though they did initially and correctly suggest a south of west track through the MDR due to ridge placement, that ridge was initially modeled to break down in the west with an advancing ECONUS trough. But that trough was overmodeled and lifted out while the WAR kept building west. Even after Irma was driven into the Leewards, there were more Carolina solutions in the ensembles than S. Florida. The majority did finally come west when the ECONUS trough was handled better. Irma eventually steamrolled the northern coastline of Cuba, and the rest is history. It's just good to keep in mind that though we're used to surprises with the global OPs swinging back and forth, ensembles do swing as well when out far enough in range.

[LakeNormanStormin]

East Coast keep your heads up.

25% chance it pushes more west 

[Windspeed]

I'm watching this region for some diurnal action tonight. It's been moistening and bubbling with low-level showers. But this is roughly the center of the broader circulation. The deeper convection to the north is increasing banding. Easterly shear appears to be easing up as well.

[WxWatcher007]

2 minutes ago, Windspeed said:

I'm watching this region for some diurnal action tonight. It's been moistening and bubbling with low-level showers. But this is roughly the center of the broader circulation. The deeper convection to the north is increasing banding. Easterly shear appears to be easing up as well.

That shallow convection was the first thing I noticed on IR. It’s definitely exhibiting a strong presentation for a wave. Won’t be long until this is a TC…and absolutely taking off. 

 

[GaWx]

1 hour ago, Windspeed said:

1 hour ago, Floydbuster said:

Wow did the ensembles really have Irma that far north? I didn't remember that at all.

Yes, at one point they did. Though they did initially and correctly suggest a south of west track through the MDR due to ridge placement, that ridge was initially modeled to break down in the west with an advancing ECONUS trough. But that trough was overmodeled and lifted out while the WAR kept building west. Even after Irma was driven into the Leewards, there were more Carolina solutions in the ensembles than S. Florida. The majority did finally come west when the ECONUS trough was handled better. Irma eventually steamrolled the northern coastline of Cuba, and the rest is history. It's just good to keep in mind that though we're used to surprises with the global OPs swinging back and forth, ensembles do swing as well when out far enough in range.

 Below is the Euro suite for 8/31/17 at 12Z, which was when Irma was close to the current longitude of 95L and when it was 10 days from S FL. Note that this was already very threatening to the US with ~3/4 of the members along with the op either threatening the FL/SE coast or going into the GOM. The mean is at 77W at 240 and still moving NW/NNW. In contrast, the furthest W today's 12Z EPS mean got was ~67W and already moving due N with only one member hitting the US:

 Also, below is a Tweet showing the 0Z 8/31/17 EPS, which was similarly highly threatening to the SE US with many members even into the GOM:

My point is that although model consensus means shifted too far north the next day as you showed, the two EPS runs were very bullish for a US hit at the 10 day point compared to the very bearish EPS runs today for 95L. Now granted, Irma was already a TS/H on 8/31/17 vs 95L being only an Invest.

[cardinalland]

Euro/CMC OP have a very different evolution than GFS OP approaching hour 240. Euro/CMC OP have a stronger 2nd tropical disturbance off to the east and not much of a high south of Newfoundland, while the GFS has a strong high south of Newfoundland and no 2nd tropical disturbance.

An out-to-sea solution seems more supported to me but I'm still keeping an eye on this one for east coast from NC to Newfoundland

 

Edit: Also wanted to add that as usual things might become more clear once the storm has actually fully formed

[MJO812]

3 hours ago, TPAwx said:

Fantastic synoptic set-up to keep this monster away from a direct US impact.

Love it!!

Don't know that yet 

[Windspeed]

Recent ASCAT. Definitely a broad center, but looks closed. Needs continued bubbling convection to tighten low-level vorticity. We'll have a TC on Tuesday.

[Castaway]

59 minutes ago, Windspeed said:

Recent ASCAT. Definitely a broad center, but looks closed. Needs continued bubbling convection to tighten low-level vorticity. We'll have a TC on Tuesday.

Nice! The general area of circulation has become more evident from watching it on and off past hours. It’s getting it’s act together.

 

 

[GaWx]

6 hours ago, Windspeed said:

6 hours ago, Floydbuster said:

Wow did the ensembles really have Irma that far north? I didn't remember that at all.

Yes, at one point they did. Though they did initially and correctly suggest a south of west track through the MDR due to ridge placement, that ridge was initially modeled to break down in the west with an advancing ECONUS trough. But that trough was overmodeled and lifted out while the WAR kept building west. Even after Irma was driven into the Leewards, there were more Carolina solutions in the ensembles than S. Florida. The majority did finally come west when the ECONUS trough was handled better. Irma eventually steamrolled the northern coastline of Cuba, and the rest is history. It's just good to keep in mind that though we're used to surprises with the global OPs swinging back and forth, ensembles do swing as well when out far enough in range.

To confirm what I think you already know:

 After aiming Irma for the SE US on the 8/31/17 EPS runs, the EPS mean moved NE for the next two days of runs to where about half recurved offshore the E coast (though the mean being near 76W wasn't nearly as far offshore as today's runs have 95L, which is near 67W and with only one member hitting):

 

 Then the next day, 9/3/17 (seven days out), the EPS started trending back to the SW and was back to being centered on FL (just as the 8/31/17 0Z run was) by the 9/5/17 0Z run!

[Windspeed]

To confirm what I think you already know:
 After aiming Irma for the SE US on the 8/31/17 EPS runs, the EPS mean moved NE for the next two days of runs to where about half recurved offshore the E coast (though the mean being near 76W wasn't nearly as far offshore as today's runs have 95L, which is near 67W and with only one member hitting):
 
 Then the next day, 9/3/17 (seven days out)  the EPS started trending back to the SW and were back to being centered on FL (just as the 8/31/17 0Z run was) by the 9/5/17 0Z run!

Yes. Obviously, we're in the grey area of mid-range modeling still. We have a signal and pattern for recurve in place. But this is still far enough out that a major steering feature might not yet be correctly simulated. Hence, why, though there is some confidence, it's not chiseled out yet. We've got a pretty strong ECONUS high right now that might stick around longer than forecast and make the trough not be as strong. A mid-level trough could also cut off. Mid-level heights in the western Atlantic could model differently in a few days versus present, even if that chance will decrease if we don't see a swing by then.

[Normandy]

I would argue we have a pattern for a north oriented recurve.  There is a blocking high to the storms NE, it just does not have a strong trough to tug it in to the coast.  Still so much to be determined there.   
 

More interesting to me than long term track are short term trends.  The storm is still very broad and moving quite quickly west.  ASCAT just hit the system and shows it near 11N.

[GaWx]

1. The 0Z GFS has 95L as a MH on 9/13 100 miles W of Bermuda followed by a big hit on Nova Scotia 9/14-5.

2. The 12Z UKMET was the westernmost major 12Z model run by 300-350 miles. Despite that, the 0Z is ~200 miles WSW of the 12Z. It is also weaker. 

 So, at 168, the 0Z UKMET is a whopping 500 miles WSW of the 0Z GFS and 450 miles W of the 0Z ICON in the SE Bahamas moving slowly WNW:

NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER  24 HOURS
              FORECAST POSITION AT T+ 24 : 13.3N  41.7W

                        LEAD                 CENTRAL     MAXIMUM WIND
      VERIFYING TIME    TIME   POSITION   PRESSURE (MB)  SPEED (KNOTS)
      --------------    ----   --------   -------------  -------------
    0000UTC 06.09.2023   24  13.3N  41.7W     1010            23
    1200UTC 06.09.2023   36  13.9N  44.5W     1007            31
    0000UTC 07.09.2023   48  15.0N  46.5W     1007            35
    1200UTC 07.09.2023   60  16.1N  48.9W     1006            34
    0000UTC 08.09.2023   72  17.0N  52.0W     1006            32
    1200UTC 08.09.2023   84  17.9N  55.3W     1006            35
    0000UTC 09.09.2023   96  18.9N  58.6W     1006            32
    1200UTC 09.09.2023  108  19.3N  62.1W     1006            38
    0000UTC 10.09.2023  120  20.3N  65.1W     1005            40
    1200UTC 10.09.2023  132  21.2N  67.9W     1004            41
    0000UTC 11.09.2023  144  21.7N  69.4W     1005            38
    1200UTC 11.09.2023  156  22.1N  71.5W     1004            36
    0000UTC 12.09.2023  168  22.7N  72.9W     1004            34

[Floydbuster]

 

Continued west motion and a center formation in the near-term could have huge impacts for the U.S. Virgin Islands on determining how close this system may get.

[Windspeed]

^ The UKMET tracks would be more favorable for long-term TC intensity, as it traverses much higher OHC versus the upwelled wake of Franklin and Idalia. I don't know if that will be any kind of precursor to a swing west in the other globals on Tuesday, however.

[WxWatcher007]

It’s subtle and verbatim probably leads to the same outcome, but the 00z Euro opens the door to more Atlantic ridging and a somewhat different E US troughing setup, allowing for a more northward rather than NE turn through 240. Again, this is all so far out it’s hard to get a strong read on anything.

[TheDreamTraveler]

1 hour ago, WxWatcher007 said:

It’s subtle and verbatim probably leads to the same outcome, but the 00z Euro opens the door to more Atlantic ridging and a somewhat different E US troughing setup, allowing for a more northward rather than NE turn through 240. Again, this is all so far out it’s hard to get a strong read on anything.

Not only is the 0z Euro more north than NE now but it's more west than the 12z by a decent margin. All it takes is a few more shifts like that to make it a threat on the euro so should be interesting to see how things develop since we're so far out. It's been a while since we've had a long tracker like this that has a slight threat to the US

[Prismshine Productions]

6z GEFS

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[WxWatcher007]

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. 

[ineedsnow]

great post!

[GaWx]

 The 0Z UKMET initialized at 12.5N, 37.4W. The Best Track had 95L  at 11.2N, 36.2W at 0Z; 11.5N, 37.5W at 6Z; and at 12.2N, 39.6W at 12Z. So, the 0Z UK initialized 1.3 further N and 1.2 further W or 120 miles NW of the Best Track position. However, 95L has moved about 3:1 W by N from 0Z to 12Z rather than moving the 1:1 of straight NW. Thus, the 12Z Best Track position is 150 miles W of the 0Z UK initialization. 

 Translation: the 12Z UKMET track may very well initialize nearly due W vs its 0Z initialization. We'll see whether or not that translates to the 12Z UK track being even further W to SW of the already far W to SW 0Z run vs the other models, but that's quite possible.

*Edited 2nd paragraph

[GaWx]

.NEW TROPICAL DEPRESSION FORMS IN THE CENTRAL TROPICAL ATLANTIC... ...FORECAST TO BECOME A POWERFUL HURRICANE BY THE END OF THE WEEK...

11:00 AM AST Tue Sep 5 Location: 12.5°N 40.2°W Moving: WNW at 15 mph Min pressure: 1008 mb Max sustained: 35 mph

0Z UKMET initialized 190 miles due east of this

[shaggy]

7 minutes ago, GaWx said:

.NEW TROPICAL DEPRESSION FORMS IN THE CENTRAL TROPICAL ATLANTIC... ...FORECAST TO BECOME A POWERFUL HURRICANE BY THE END OF THE WEEK...

11:00 AM AST Tue Sep 5 Location: 12.5°N 40.2°W Moving: WNW at 15 mph Min pressure: 1008 mb Max sustained: 35 mph

0Z UKMET initialized 190 miles due east of this

Correct me if I'm wrong but the ukmet tends to have a W bias with tropical systems correct? I remember when the ukmet was the only model showing Irma reaching the north coast of Cuba. 

Winder where the other 12z suites will initialize their centers.

[Joe4alb]

[GaWx]

20 minutes ago, shaggy said:

Correct me if I'm wrong but the ukmet tends to have a W bias with tropical systems correct? I remember when the ukmet was the only model showing Irma reaching the north coast of Cuba. 

Winder where the other 12z suites will initialize their centers.

 I remember it and the Euro both being W of the other models and thus those two doing the best for Irma in FL overall once within 5 or so days of landfall. Actually for Ian last year for both the FL and SC landfalls, the UKMET was further right rather than further left of the model consensus and it did the best. Also, for Idalia, the UK was right of the GFS/CMC and did better. So, I don't know whether or not it still has a too far W bias. Maybe it still does in the longer range out in the MDR though.