Windspeed

Already at the "F" named storm and we didn't even make a thread. We have not seen anything crazy at this point, but it's not exactly been quiet either. Felicia is intensifying and expected to become a hurricane by tomorrow. No threat to land. I am sure someone will want to post "bye" when it dissipates over cooler surface waters next week.

There's a good discussion ongoing about 2021 following suite with 2020, '18, '16, that late September through October will experience peak activity versus a traditional climo-favored late August to mid September peak. This would not surprise me in the least. Especially if there is robust MDR warming in September versus typical late July-August and heft poleward motion of the ITCZ. A slightly below average MDR SST anomaly is currently in place. That may be the only other negative factor against early CV August activity beyond PVs and SAL. Though we are still weeks away and slightly below mean SST data sets can reverse pretty quickly given a few weeks of decreased low level easterlies.

With a -ENSO in place, an active August may hinge upon whether the EPAC enters a suppressed regime while a strong WAM continues in the EATL. If PV anomalies are somewhat in check across the Atlantic Basin, then CV season likely kicks off early. Current Bermuda High placement is already a potential harbinger of Caribbean Cruisers. Any subtropical development could threaten Florida, but any deep MDR development likely would maintain Caribbean potential. I expect more Caribbean hurricanes this season. Weak PV anomalies and a suppressed EPAC would obviously increase their ACE potential by mitigating VWS. To further add upon this, note these graphics by Ben Noll: Keep in mind that sinking air is only prohibitive of TC development in the genesis stage. With modeled subsidence in August across the EPAC, this may squash TCG occurring there and subsequently qualm outflow induced VWS across the Caribbean and Antilles into the Subtropical Atlantic. Likewise, with atmospheric instability / lift in the EATL coinciding a +WAM, TCGs will be supported from frequent healthy tropical disturbances rolling off the African Continent. Granted, limiting factors such as strong PVs and SAL can still work against potential TCs crossing the MDR, but if those factors are limited, a TC will have no issues intensifying into the WATL. Timing of occasional favorable CCKWs enhance these regardless of overall airmass regime. At least at this point, an active August looks possible, and certainly a hyperactive September is in the cards as well.

[emoji102]

You joke but... In all seriousness, a cool upper level low can allow for some pretty intense lapse rates and thunderstorms this time of year over the hot coffee thermos that is Florida.

Convective organization consolidated into an eyewall is usually seen and needed to sustain the vortex of the tropical cyclone at ≥74. But that isn't always the case. We have seen eyewalls form in core convention in moderate tropical storms that were only producing 50-55mph winds. Likewise we have examples of hurricanes with broken cells around the vortex that were not producing a solid or even semicircle eyewall. Again, it is not merely the appearance and structure that classifies a hurricane; in situ wind data (or satellite derived estimates, if that is only available) and a closed warm core surface vortex are the requirements for TC classifications.

^This too.

Elsa had stronger surface-based convergence and trade winds on the northern semicircle of its closed circulation than Andrew had in its initial intensification phase. Background in situ tropospheric conditions are just as important as the surface vortex barometric forcing in a tropical cyclone for surface winds. Not all TCs evolve the same. Environment matters as do wind obs.

The classification has never changed. ≥74MPH sustained surface winds in a tropical cyclone is classified as a hurricane/typhoon depending on basin.

Rare that it survived the Caribbean as a classified tropical storm this time of year. Rare it reached hurricane intensity more than once while surviving land interaction this time of year. It's also worth reiterating how damn crazy Hurricane Dennis was in 2005, which reached Cat 4 intensity in the Caribbean and made landfall as a Category 3 in the Florida Panhandle sixteen years ago today.

Look out, Jacksonville...

Yikes...

Charley was already well-organized and made landfall as a hurricane in Cuba. Elsa, though convectively active, is still yet to put itself in a position to intensify rapidly. Now could that occur? Sure. But it needs to be developed to really take advantage of diffluence. Otherwise, it's high end TS to minimal hurricane at best. I don't think this will be a Charley. Too much against it.

Center/LLC relocations are allowing Elsa to thread the needle, but at the same time, such reorganization can take time to respond with pressure falls and intensification. Despite the present more symmetrical convective envelope, banding and a healthy MCS, Elsa needs to chill with the break down and reformation of low-level vorticity maximums before it's going to experience a prolonged period of reintensification.

Yeah I think they just missed earlier due to fast rate of motion and small low-level vortmax.

Convection is trying to wrap upshear around the LLC. The mid-to-upper easterly flow might be starting to amplify now. We'll see if that can counter the high speed low level flow somewhat for less of a deep layer tilt to the vortex. May still remain somewhat weak regardless.

28 mph is just screaming in the tropical latitudes. I cannot imagine Ela wrapping convection upshear quickly as the system continues at that forward speed but who knows? The mid-to-upper easterly flow may also ramp up tomorrow and allow more alignment / stacking. Either way this probably remains status quo the next 24-36 hrs. Here is a good thread by Papin on Elsa: Here is new video up by Cowan as well:

No.

Beven has a high degree of uncertainty on intensity mainly due to the strong easterly flow that will be kicking hard as this system traverses the Caribbean. A potential motion of 22-25 kts is screaming. That being said, if PTC 5 develops faster in the short term and increases intensity potential for the Lesser Antilles, it could maintain itself within that fast embedded flow. Anything from a weak TS to a Cat 2 by the time this is south of Haiti. So yes, a very problematic intensity forecast for now.

^ Of course, the Euro may be about to miss on an early TCG here. It's not perfect and does strike out occasionally. There is clearly good low level convergence now occurring within the southern envelope of the wave axis and monsoonal trough. The northern envelope of the wave appears to be folding and breaking away from the ITCZ, which is dragging behind 95L to the WNW of 97L. In short, we have a decent cyclonic spin to this system already; whether it presently has a closed low level vortex, that may not be far off with convective bursting near a hypothetical center tonight.

Ridge placement is such that if 97L develops, it's going to be a Caribbean runner. Typically with a pronounced surface and 590s DM ridge, you get strong low level easterlies in the Caribbean. Climatologically speaking, we still have westerlies screaming over top creating strong shear for anything that might develop, aka the Caribbean graveyard this time of year. But with a potential CCKW in place, increased instability and potential upper level easterlies may coincide through the Caribbean as well. Upper ridge placement could pull off a surprise here. Not to get too far ahead (TCG is still not climatologically favored), but similar rare occurrences and synoptic favoribility have happened. The last anomalous July was 2005. We got Dennis and Emily that year.