My current impression is that
most of the negatives that people have identified (regardless of how influential they are) should go away with time -- it's just a question of how soon they do.
- Northward displaced ITCZ, which sends waves into cooler, dryer parts of the Atlantic? Climo says it always moves back south as the season progresses (and the eastern ITCZ over Africa has already done so).
- Overly strong African Easterly Jet? It also gets weaker over time as per climo, and models are hinting at that.
- Warm tropopause? They will cool down more quickly than the ocean does.
- El Nino-like mid-latitude atmosphere (if we agree with a single tweet from Andy Hazelton about it)? SOI is positive now, in line with a classic La Nina, so the atmosphere should respond soon. (I'd also say wind shear patterns so far already resembles much more of a La Nina than an El Nino.)
The only thing that seems less certain is upper-level patterns in the extratropics, being it a persistent +NAO or a Scandinavian block. However, not only is that
not universally agreed upon, but
current NAO forecasts show a return to neutral or slightly negative, so there are hints that whatever pattern that may have dumped dry air southward into the Atlantic could also be changing soon.
It's important to remember that many solidly positive factors for seasonal activity are still in place. The MDR is still anomalously warm with record OHC; shear is still generally low across the tropical Atlantic; and we still have healthy waves emerging from Africa. Currently, I don't see any reason why they wouldn't continue to cooperate once the other inhibiting factors -- whatever they are -- start fading away. (Plus, if people are making the argument that "waters are always warm enough for a hurricane", then waters that are warmer than a typical late season should also support a hurricane later than a typical season does.)
Putting all this together...
Yes, I still expect the second half of the peak, and the late season, to be more active than usual and help the basin catch up.Whether such changes start on September 5, September 10, September 20, October 1 or October 15, who knows. But historically, there's been no shortage of strong hurricanes (even strong CV hurricanes) during late seasons, even
(and perhaps especially) in recent years. Maria formed on 9/16, Sam 9/22, Lorenzo 9/23, and Matthew 9/28 (though not so much in the MDR). Late-season Caribbean activity is always another beast, especially with a more established -ENSO/La Nina than now. And just last year, even with the western basin shut down by Nino shear, Hurricane Tammy formed on October 18 in the MDR.
It remains a question whether we can hit enough ACE to be above-average (only need 71 more), hyperactive (104.5 more), 200 ACE (144.9 more) or CSU's forecast numbers (174.9 more). The later in the season, the more likely storms will either recurve early or form further west, both resulting in less time over water and thus less ACE per storm. There's also a question of whether the season can produce enough hurricanes (9 more) and majors (5 more) to hit CSU's forecasts; I do think the 23 NS forecast is probably toast.
But the bottom line is...
There remain plenty of ways for the season to be active and/or memorable. I would absolutely not be surprised if late September behaves like a typical early September, which would actually be in line with both the anomalous SSTs
and the anomalous ITCZ positions.
Or something like that.
