2023 - tracking the tropics

[Typhoon Tip]

1 hour ago, WinterWolf said:

Yes I do agree at this early stage. Thing isn’t even a depression yet. And days and days away from even approaching the east coast. But things need to keep evolving to have a legit shot. The next few days will be telling for sure.  Very Low confidence currently anything can come of it, but still too early to be ruled out completely. 

The problem I have with 'repeat time' or 'over due' and the like is that they are wholly an artifact of linear statistics - taking linear averages doesn't apply to reality.  

Because, pretend for a moment there have been 30 hurricanes on the EC over 300 years, that means you get to have fun and excitement every 10 years or your due?

wrong. 

All that means is, spanning that particularly sample set, if you divide the total years by the number of occurrences you got the number 10.  It really doesn't mean anything beyond arithmetic result - the only thing stopping the definition of an arbitrary number is that yeah ... hurricanes have happened on the EC over that 300 years. Nothing else. 

If we look back, there are 30 or 60 or 20 year intervals where there may have 5 or more. Then spans with less... It really means vastly more significance if we can identify the eras where the 5 or more (or less..) are favored.  Then, if you're cruising through one of those periods and missing out, then "maybe" the "due" has more meaning relative to that period which was suggested to have performed better.   But that kind of deeper conditional analysis is not happening in here...lol.

[ineedsnow]

AL132023 - Tropical Depression THIRTEEN

[WxWatcher007]

Did a long post in the main thread. Keep expectations in check. I was intrigued this morning to see the subtle shifts on the Euro, even if the end result verbatim is still OTS. 

10 minutes ago, 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. 

 

[STILL N OF PIKE]

Thanks for posting your thoughts . 

[MJO812]

3 hours ago, ineedsnow said:

some of the 6z GEFS showing how the east coast can get it done

And eps

[weatherwiz]

2 minutes ago, MJO812 said:

And eps

I feel like even when the Mets are mathematically eliminated from the playoffs you still try and find a way of how they can get in.

[ineedsnow]

wow for a first advisory 

EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 125 NM
ON DAY 4 AND 175 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY

OUTLOOK VALID 09/1200Z 19.4N  59.1W
MAX WIND 115 KT...GUSTS 140 KT.

OUTLOOK VALID 10/1200Z 21.5N  63.5W
MAX WIND 120 KT...GUSTS 145 KT.

[ineedsnow]

FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z 12.5N  40.2W   30 KT  35 MPH
 12H  06/0000Z 12.8N  42.1W   40 KT  45 MPH
 24H  06/1200Z 13.6N  44.7W   50 KT  60 MPH
 36H  07/0000Z 14.4N  47.2W   60 KT  70 MPH
 48H  07/1200Z 15.3N  49.7W   70 KT  80 MPH
 60H  08/0000Z 16.2N  52.2W   80 KT  90 MPH
 72H  08/1200Z 17.3N  54.7W   95 KT 110 MPH
 96H  09/1200Z 19.4N  59.1W  115 KT 130 MPH
120H  10/1200Z 21.5N  63.5W  120 KT 140 MPH

[WxWatcher007]

120kts and below the guidance consensus  

This is going to be a monster.

[ineedsnow]

Tropical Depression Thirteen Discussion Number   1
NWS National Hurricane Center Miami FL       AL132023
1100 AM AST Tue Sep 05 2023

Satellite images indicate that the tropical wave (Invest AL95) that 
we have been following for several days has become better organized 
this morning, with many curved low-level banding features.  A 
partial scatterometer pass near 1201 UTC indicated a well-defined 
center had formed, with winds speeds of about 30 kt.  Thus, 
advisories have been initiated on Tropical Depression Thirteen, and 
the current intensity is set to 30 kt.

The depression is moving west-northwestward at about 13 kt.  A 
mid-level ridge over the central Atlantic is expected to persist to 
the north of the tropical cyclone, keeping the system moving with 
this general motion through Saturday.  The spread in the model 
guidance is remarkably low for a first advisory, and the official 
forecast is near or west of the model consensus.  However, it 
should be noted that the NOAA corrected-consensus aids and some 
ensemble members are still to the left of the official forecast, so 
it is too early to determine exactly how close this system will get 
to the Leeward Islands given the average track forecast error at 
those time ranges.

The environment around the depression appears to be conducive for 
strengthening.  The only obvious hindering factor is 
light-to-moderate northeasterly shear, which should keep the 
intensification rate in check in the short term.  However, in two to 
three days, this shear is forecast to relax with an upper-level 
ridge building near the cyclone, and the system should be moving 
over record-warm waters of near 30 deg C east of the Lesser Antilles 
(that would look more in place in the Gulf of Mexico).  These 
factors could support rapid intensification by the end of the week, 
although it too early to determine exactly when this might occur 
until a better-defined inner core forms.  The NHC intensity forecast 
is extremely bullish for a first forecast, but remarkably lies 
below the intensity consensus.  All indications are that the 
depression will become a strong hurricane by the end of the forecast 
period.

KEY MESSAGES:

1. The depression is forecast to become a major hurricane by 
this weekend and could bring impacts to the Leeward Islands by that 
time. While it is too soon to determine the location and magnitude 
of these possible impacts, interests in this area should monitor 
the progress of the depression and updates to the forecast.

[MJO812]

12 minutes ago, weatherwiz said:

I feel like even when the Mets are mathematically eliminated from the playoffs you still try and find a way of how they can get in.

This storm is still at 200 hours out. Whoever  throws in the towel this early is foolish.

[weathafella]

4 minutes ago, MJO812 said:

This storm is still at 200 hours out. Whoever  throws in the towel this early is foolish.

There are piles of clean towels at the cabana..

[dryslot]

Is it coming?

[weatherwiz]

2 minutes ago, dryslot said:

Is it coming?

does cirrus from the outflow count?

[dryslot]

1 minute ago, weatherwiz said:

does cirrus from the outflow count?

There's so many negative factors why a major hurricane never gets into New England, Odds are so minuscule.

[weatherwiz]

1 minute ago, dryslot said:

There's so many negative factors why a major hurricane never gets into New England, Odds are so minuscule.

There is a lot that has to go right. It's also not only about having the right pieces in place but the evolution of those pieces have to be just about perfect. It's one thing to get the pieces but it's a whole another ballgame to get everything to evolve perfectly. 

[dryslot]

3 minutes ago, weatherwiz said:

There is a lot that has to go right. It's also not only about having the right pieces in place but the evolution of those pieces have to be just about perfect. It's one thing to get the pieces but it's a whole another ballgame to get everything to evolve perfectly. 

Its way worse then trying to thread the needle on snowstorms, To many factors need to go right.

[weatherwiz]

Just now, dryslot said:

Its way worse then trying to thread the needle on snowstorms, To many factors need to go right.

Yup...winter we can definitely do it, tropical...not so much. 

[Typhoon Tip]

2 minutes ago, dryslot said:

Its way worse then trying to thread the needle on snowstorms, To many factors need to go right.

It's funny you said this for me, because I was just musing the other day ... pretty much exactly this sentiment.  The odds for this sort of thing/tropics working out has gotta be longer than even threading an open wave cyclone in the winter

[Cyclone-68]

What would be more likely here? A midwestern/plains severe weather  event or a cat 2 in a given year?

[WxWatcher007]

3 minutes ago, Cyclone-68 said:

What would be more likely here? A midwestern/plains severe weather  event or a cat 2 in a given year?

Severe weather.

[FXWX]

45 minutes ago, dryslot said:

Its way worse then trying to thread the needle on snowstorms, To many factors need to go right.

Agree 1,000%...

[FXWX]

51 minutes ago, weatherwiz said:

There is a lot that has to go right. It's also not only about having the right pieces in place but the evolution of those pieces have to be just about perfect. It's one thing to get the pieces but it's a whole another ballgame to get everything to evolve perfectly. 

Yup...

[FXWX]

57 minutes ago, weatherwiz said:

There is a lot that has to go right. It's also not only about having the right pieces in place but the evolution of those pieces have to be just about perfect. It's one thing to get the pieces but it's a whole another ballgame to get everything to evolve perfectly. 

I used to always tell my students "Does the door open at the right time / is there something in a position to go through the door".  Almost every summer and early fall we see the door wide open but there is nothing in position.  We actually do see the tropical door swing open on a regular basis, but the vast majority of the time there is not a system ready to enter.  This past July the door to the tropics was wide open for an extended period of time, but as one might expect in July, the tropics were not ready to deliver.  

[weatherwiz]

2 minutes ago, FXWX said:

I used to always tell my students "Does the door open at the right time / is there something in a position to go through the door".  Almost every summer and early fall we see the door wide open but there is nothing in position.  We actually do see the tropical door swing open on a regular basis, but the vast majority of the time there is not a system ready to enter.  This past July the door to the tropics was wide open for an extended period of time, but as one might expect in July, the tropics were not ready to deliver.  

Great analogy! That provides a visual which is quite simple to understand. 

[Typhoon Tip]

I can't count any longer how many times I've gaped in awe at a Bahama Blue pattern ...and thought- if only..

[CoastalWx]

Too bad the trough we hoped and wanted lifts out on the GFS op. 

[CoastalWx]

Looks like ridge builds to the east and helps it brush ern areas.

[WxWatcher007]

Even if the trough were perfectly oriented and perfectly timed I wouldn’t believe it at this range. 

[MJO812]

Just now, WxWatcher007 said:

Even if the trough were perfectly oriented and perfectly timed I wouldn’t believe it at this range. 

We track