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2021 Atlantic Hurricane Season Tracking Thread


WxWatcher007
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Alright, after about a month, it's time to talk tropics seriously again. 

First--let's take a look at the basin. In the last month, we've seen quite a bit of warming, which is typical, and with El Nino highly unlikely, the peak of the season has strong signals to see continued reduced shear that favors an active peak, which I personally classify between August 20 and October 20 (note--that's what I base my annual peak season forecast off of).

WOx7rGJ.png

July and early August are times for the basin to simmer, and simmer it did. It's not as warm as last season, which is why I am likely to base the peak as shy of hyperactive, but for another year, conditions thermally look to be most robust near the US coast and in the homebrew region. 

lYsbWYl.png

2021219at.jpg

 

Below are a few images from the latest CSU hurricane season forecast, which I think are helpful in providing an additional picture of where the basin is with regard to signals for the coming peak. Above average, but short of hyperactive. Note the extreme drop in shear that led to the historic 2020 peak we saw in September and October. 

5zCwf2q.png

9OVGY4V.png

As we approach the 2021 peak, the basin is waking up. We're moving into a favorable MJO phase, and enhancement we're seeing that has moved the EPAC into an active period is making its way toward the Atlantic. 

After a few misfires (Invests 91L, 92L, and I suspect 93L), the Atlantic Basin has produced an area of interest that I believe has a better than even chance of some development. Designated as 94L less than 24 hours ago, I've been watching this little wave at the western edge of a monsoonal trough as guidance had an oscillating signal on whether development could come from it over the last half week or so. 

giphy.gif?cid=790b7611bfe7d668ecd7e35cd5

An objective assessment would reveal that this invest isn't particularly special. Vorticity is just decent, the convection is disorganized, and the system is small, which makes it prone to disruptions that could kill it before it ever tries to get off the ground. Although the shear looks minimal for the immediate path ahead, big challenges remain. 

First, you have dry air that is lurking. The image below is a mid level water vapor snapshot which shows all of the invests within the monsoon trough have effectively been starved of convection, which, of course, aids greatly in lowering pressures and creating an organizational feedback loop (for lack of a better term) within a center of low pressure. 

jp0MiTh.jpg

 

If that wasn't enough, then you have the Greater Antilles, which the latest GFS envisions a collision course with Haiti/DR and Cuba. 

2D5Fpk2.png 

So why am I even posting about this little critter then? Well, because TC genesis is neither linear nor static. Like Elsa, a poor environment in one part of the Atlantic doesn't necessarily prevent genesis or development in another. Sometimes you just have to survive.

That's just what we've seen in some of the recent guidance. Although there are serious questions about how sheared anything would be as it approaches the US due to PV streamer (upper level low), the guidance while bouncing around seems to be giving 94L a greater chance of some minor development. 

There's actually not a lot to discuss seriously because there is so much that can change depending on track and potential development location, but for illustrative purposes only let's look at the 18z GFS, which has been fairly consistent with the general evolution of 94L. 

giphy.gif?cid=790b76116ba64fa84ec334ae52

What do we see? Well, early on you see 94L trying to tighten up, and it looks like it does so in time just to hit PR or one of the other major islands. That causes obvious weakening, and there isn't a lot of development as the system is driven WNW by a strong ridge until a trough creates a weakness that pulls it up the coast. Still a lot to sort out there.

It isn't until it is along the SE coast more significant development looks to take place.

What does it all mean?

At this point my takeaways are the following:

1) 94L looks to be the wave that has the best chance of coming out of the monsoon trough and developing into a weak system because it is in the best shear/moisture/SST environment. Development is not a guarantee, though. 

2) Interaction with the Greater Antilles and a possible PV streamer will have a significant impact on the overall evolution of the system.

3) The presence of a strong ridge likely means this is driven WNW, and the timing and strength of an incoming trough will have an impact on whether 94L (should it develop) is able to (re)develop in the Gulf or off the East Coast. 

 

The ceiling for this one seems low, but we're tracking again. A lot to watch for as we get an appetizer before the main course arrives. 

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Definitely making a run at TC genesis. It's in a low shear environment overall but look at those cloud tops getting blown away to the north. Shear isn't too far away. 

200.webp

There's still a good bit of uncertainty over what this looks like when it gets to the western Atlantic. 

giphy.gif

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I just saw the EPS. I think it should also be noted that there's potential on the other side of this system too. This really is just the leadoff of what should be an active period. With the steering pattern as it is, we are likely to see East Coast threats further in August if systems develop in the western MDR. 

giphy.gif?cid=790b76115fe2376d74d112a540

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Interesting thread. I agree that it's possible for this to slide further west into the Gulf, but I don't think it's likely. The operational guidance (for those that are lurking, I mean the GFS, Euro, etc.) in general has been consistent and more important--has stayed within the range of track possibilities outlined by both the ensembles (GEFS, EPS).

The huge caveat here though is we're tracking a Potential Tropical Cyclone. TC genesis has not officially occurred yet, though recon is en route right now to confirm. Once we have more data and a well-defined center, we can have greater confidence in eventual track. We've seen situations before where you get a center a little further north or south and it can make a difference in intensity which can make a difference in track. 

I think one thing for this region to watch, is the sharpness of the curve. I think there's a pretty high chance this ridge pushes this into the Gulf, but there's a split in what happens after that. Does this end up being a sharper recurve that brings remnants to the region or does the GFS have the right idea and the ridge actually pushes this almost due north and washes it out quickly. I think that's entirely up in the air at this point. 

GEFS

giphy.gif?cid=790b761151f7bf7dec44982169

 

EPS

giphy.gif?cid=790b7611800519c1cfe91fe79d

 

While we're at it, once again I want to note the signal on both ensembles for a follow up wave right after this one...

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Just putting out ideas and if a trend to the gulf starts showing up then we can say it was for the reasons outlined in that tweet. 
 

money thing about a gulf hit over a east Fl scraper is that recurve OTS goes away and improves chances for the MA to get leftovers. If it stays more East then we usually miss that. 

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27 minutes ago, H2O said:

Just putting out ideas and if a trend to the gulf starts showing up then we can say it was for the reasons outlined in that tweet. 
 

money thing about a gulf hit over a east Fl scraper is that recurve OTS goes away and improves chances for the MA to get leftovers. If it stays more East then we usually miss that. 

Oh yeah, I appreciate the tweet thread. Always good to throw out ideas. 

Totally agree on the Gulf hit. I know some of you got fringed in Elsa, but that was impactful up here in my neck of the woods. That's part of the reason why I am discounting the GFS solution for inland impacts for now. 

Tallahassee to Detroit Express doesn't really fit climo :lol: 

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4 minutes ago, WxWatcher007 said:

Oh yeah, I appreciate the tweet thread. Always good to throw out ideas. 

Totally agree on the Gulf hit. I know some of you got fringed in Elsa, but that was impactful up here in my neck of the woods. That's part of the reason why I am discounting the GFS solution for inland impacts for now. 

Tallahassee to Detroit Express doesn't really fit climo :lol: 

You're basically the only person I go to for my tropical info. You kill it. 

94L is looking like it's trying out there. Come on, baby. Bring some interesting weather. 

 

 

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Reposting this here because it's a great find. 

37 minutes ago, LoboLeader1 said:

 

 

4 minutes ago, dailylurker said:

You're basically the only person I go to for my tropical info. You kill it. 

94L is looking like it's trying out there. Come on, baby. Bring some interesting weather. 

 

 

Thank you! It's good to know my lack of sleep is actually creating something of value for people. 

Also, for folks reading, here's the 06z EPS. Remember it only goes out 6 days, but note that now we're starting to see stronger ensemble members show up. Far from a lock, but that's definitely something to watch. 

U0a1E1h.png

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Posted this in the tropical weather thread but this more or less is the main thread after the uh interesting adventures of Ampedvort and friends. 

514202826_IRLoop-PotentialTropicalCycloneSIX-GoogleChrome8_10_20219_33_35AM_LI.thumb.jpg.b3e4e75c21ae156eb6fdaf75725647ac.jpg

Might be overanalyzing but seeing some new towers in the forward and almost underside of the storm. Maybe this might is hinting at the storm getting its act together?

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