End of July Tropical Update
It's time to turn the page to August, and that means a deep dive into where we are and where we may be going as we approach the start of the climatological peak of the the 2022 Atlantic season.
It has been nearly a month since the last named storm in the Atlantic (Colin) and it is immediately apparent why.
While the EPAC is HOT, the Atlantic is about as dead as you can get.
It has been a banner month in the EPAC, where virtually everything that tried to develop in the basin has developed. The EPAC has seen 5 named storms in the month of July, and 4 have become hurricanes with 2 of those majors. That puts the basin about a month ahead of both hurricane and major climo overall.
The background environment has allowed for rising motion that strongly favored convection in the Pacific. Think MJO. It has been steadfast in supporting EPAC activity. The rule of thumb is when one basin is hot, the other is quiet in our part of the world, and that has certainly been the case in the Atlantic where sinking motion, lack of stalled fronts off the SE and Gulf, and monsoon trough along the African coast allowing for SAL in the MDR have suppressed not just activity, but convection itself--the seeds of a TC.
It's hard to state just how bad this pattern is for the Atlantic currently.
Even though this tends to be the downward peak of dry air in the Atlantic, it is extraordinarily dry. You can see it in the satellite image above, but you really see it with the SAL Analysis.
It's nearly impossible to get anything anywhere outside of the Gulf with this environment. The MDR, Caribbean, and even western Atlantic/SE coast are dry. To be clear, it's more complicated than just dry air. Combined with other factors like stability in the region, it's a toxic combo for any wave trying to form. To make matters worse, there is a nasty ribbon of shear that would rip anything apart in the Caribbean (normal this time of year) and anything that tried to develop and move westward in the eastern MDR.
It's easy to look at these plots and feel the urge to cancel the rest of the season. How could the Atlantic recover with that kind of dry air and stability in the MDR? How could we see long track hurricanes with shear this high?
I strongly urge caution in cutting back forecasts for an above average season.
1. Generally Speaking, a Quiet Atlantic This Time of Year is Climo
There's no way to sugarcoat it: the current Atlantic pattern is truly awful for TC genesis. That said, this time of year the pattern usually leaves a lot to be desired. In recent years, very active years by the way, we saw fairly dramatic pauses in Atlantic activity during this time. Although the season starts on June 1, by the time we get to August 1, we still have approximately 90% of tropical activity that is yet to occur.
July tropical activity is almost exclusively confined to the homebrew regions of the SE coast, Gulf, and Western Caribbean for a reason--the broader basin is not ready for major activity via African waves in the Atlantic and Caribbean portions of the MDR. That means it's folly to make a prediction on what August and September will look like with regard to ACE and absolute TC numbers based on July activity.
Image courtesy of Michael Lowry.
2. Signs are That the Basin Will Gradually Become More Favorable
Now, this one is easy. We're headed toward the peak of the season, which broadly runs from August 20-October 20. Usually the switch flips and we go from quiet to very active.
The PAC will not continue on this heater, and while we had a false start signal from the models about two weeks ago that highlighted the end of July/early August as the period the switch would flip, it's important to look at the puzzle pieces they try to throw out.
First, it's looking like rising motion will become more favorable by mid-month in the Atlantic and favor more vigorous waves off Africa, right in time for the start of CV season in the Eastern Atlantic (image courtesy of Andy Hazelton). This is critical, because we will need moisture to get injected into the basin.
second, it looks like shear will begin to decline. This is consistent with -ENSO climo, so it wouldn't be a surprise that things begin to change as we get closer to the peak.
Things are rough according to an EPS mean at the start of August, but as we get closer to the peak, the signal is for a less hostile basin.
3. Despite Mixed Environmental Factors, ENSO and SST/OHC Still Rule the Day
Finally, ENSO still matters. We are going to see a La Nina/-ENSO state during the peak of the season. This is clear and unambiguous. Normally, -ENSO produces a broadly favorable environment. I will note that @GaWxhas done some excellent work that challenges the premise that a third-year Nina must necessarily be active, but I do think that an active WAM, reduced shear typical of a Nina, and importantly, near normal MDR/cool subtropics and warm western Atlantic will allow for an above average (but not hyperactive) season.
I started the season with a 21 named storm/10 hurricane/5 major hurricane forecast, and I don't see much reason to change that right now. I do think we get some activity before the climb toward peak begins on August 20. Overall, I think stability in the MDR will take the longest to overcome, but the other factors I listed above should be able to overcome that. As I've said the last few years as well, I think a relative lack of activity in the Eastern Atlantic can be countered by increased activity in the western Atlantic, where SSTs and OHC are higher than usual.
I should note that my usual TCHP charts are inaccessible, but based on what I saw earlier in the month, the depth of ocean warmth is on par with our other recent active seasons, especially in the western Atlantic.