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webberweather.bsky.social @webberweather.bsky.social · 4d

I wonder where the Rossby Wave Train is

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webberweather.bsky.social @webberweather.bsky.social · 8d

Also, if you haven't played around with it much, Climate Engine is a very powerful tool.

www.climateengine.org

ClimateEngine.org

www.climateengine.org

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webberweather.bsky.social @webberweather.bsky.social · 8d

Yeah I think so, esp. when coupled w/ better instability in late Sep as you noted earlier.

Also doesn't help our AEW train has been anemic this yr, a S2S boost likely would have helped.

In fact, much of W Africa has been record dry this summer, more akin to the big drought years of the 1970s & 80s

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webberweather.bsky.social @webberweather.bsky.social · 8d

Likely was some AEW energy dispersion behind #Gabrielle too as the waves that triggered #Humberto & #Imelda were immediately trailing. (Fig is pre-#Gabrielle ~40W)

This is consistent w/ my undergrad advisor's research which showed stg AEWs come in packets of ~3

journals.ametsoc.org/view/journal...

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webberweather.bsky.social @webberweather.bsky.social · 8d

TC activity in the Atlantic normally isn’t dependent on S2S conditions in the moment. There‘s almost always a lag between an MJO/CCKW passage and TCs. In this case, the seedlings for #Imleda & #Humberto developed in the prior CCKW passage before finding favorable “enough” conditions later to develop

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webberweather.bsky.social @webberweather.bsky.social · 9d

This is something I talked about a few months ago.

bsky.app/profile/webb...

webberweather.bsky.social @webberweather.bsky.social · Jul 21

The stars are aligning on a seasonal and subseasonal scale for this year’s Atlantic Hurricane Season to be pretty underwhelming compared to normal thru early-mid Sep ish, while also finishing quite strong late Sep into Oct.

Current SSTa pattern, MJO/S2S variability, & analogs all support this.

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webberweather.bsky.social @webberweather.bsky.social · Aug 22

This dry air has finally caught up to 99L this morning

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webberweather.bsky.social @webberweather.bsky.social · Aug 22

I'll be the first to admit, although some things like the CCKW passage & SSTs are decent, I'm somewhat surprised #99L is doing this given the big SAL/dust outbreak that's been chasing it from the NE.

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webberweather.bsky.social @webberweather.bsky.social · Aug 22

#99L is certainly a tropical cyclone if I've ever seen one.

Prominent curved banding under the hood w/ persistent, continuous, & highly concentrated vortical bursting over the same part of the wave axis are dead giveaways that a strong, closed, & coherent low-level vortex exists

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webberweather.bsky.social @webberweather.bsky.social · Aug 16

This is a very slippery slope because if the our trailing TC misses the upwelling path even a little bit, it actually has the opposite effect on heat content via a deeper ocean heat pump.

journals.ametsoc.org/view/journal...

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webberweather.bsky.social @webberweather.bsky.social · Aug 16

Another favorable indicator:

A potential vorticity streamer breaks off downstream of #Erin's upper level anticyclone & mirrors this wave as it marches towards the Antilles.

This will favor strong upper-level divergence that should fuel greater convective heating over the wave axis.

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webberweather.bsky.social @webberweather.bsky.social · Aug 16

Other things that favor development here:

This wave's moisture envelope is rather large & should help insulate it from dry air intrusions to the north/northwest...

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webberweather.bsky.social @webberweather.bsky.social · Aug 16

Beyond #Erin, this tropical wave leaving the coast of Africa will be the next system to watch in the Atlantic.

The overall environment looks quite favorable for development as this reaches the Central Atlantic later this week, esp. as a Kelvin Wave (blue contours, right) passes overhead

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webberweather.bsky.social @webberweather.bsky.social · Aug 16

#Erin is just a downright incredible hurricane.

I cannot remember the last time I tracked an Atlantic hurricane with a pinhole eye this small & stable/persistent since at least Wilma (2005).

This evening's recon flight into #Erin ought to be very interesting to say the least

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webberweather.bsky.social @webberweather.bsky.social · Aug 13

I suspect the low to mid-lvl portion of the CCKW leaving #Erin behind had something to do w/ today's struggles

Not seeing as much lift, moistening, & /or KW-induced cooling in the dust-driven trade wind inversion ~800mb exacerbated the stability problems imho

misva.aeris-data.fr/products/syn...

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webberweather.bsky.social @webberweather.bsky.social · Aug 11

Equatorward propagating Rossby Wave Trains like this within the subtropical jet over Northern Australia is one of the most common pathways for Kelvin Waves development in the boreal summer.

See:

journals.ametsoc.org/view/journal...

journals.ametsoc.org

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webberweather.bsky.social @webberweather.bsky.social · Aug 11

A Convectively Coupled Kelvin Wave that developed within the Subtropical Jet Stream over Northern Australia will likely pass over the Atlantic ~Aug 20

This will favor more opportunities for tropical development late month as a series of strong African Easterly Waves immediately follow behind #97L

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webberweather.bsky.social @webberweather.bsky.social · Aug 11

There will likely be at least more opportunities for tropical development immediately behind #97L as a Kelvin, Rossby, and MJO wave simultaneously pass over Africa this week.

Also, upstream wave dispersion from #97L will only help further amplify the AEW train over Africa

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webberweather.bsky.social @webberweather.bsky.social · Aug 11

This has been a TD for about 12-15 hours already yep.

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webberweather.bsky.social @webberweather.bsky.social · Aug 11

Flooding from Invest #97L caused 6 deaths in the Cabo Verde Islands.

Probably would have been a good idea to use the “PTC” designation here.

expressodasilhas.cv/pais/2025/08...

Seis mortos e danos generalizados causados pelo mau tempo em São Vicente

Pelo menos seis pessoas morreram, vítimas das fortes chuvas que caíram durante a última noite em São Vicente, acompanhadas de trovoadas e relâmpagos intensos. Quatro das vítimas são crianças. As infor...

expressodasilhas.cv

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webberweather.bsky.social @webberweather.bsky.social · Aug 11

I suspect the low-level/convergent portion of a Kelvin Wave is already hitting invest #97L out over the Cabo Verde Islands, giving it an additional instability boost against marginal SSTs

Last night's ECMWF 700mb fcst for 0z this evening depicts this quite well

misva.aeris-data.fr/products/syn...

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webberweather.bsky.social @webberweather.bsky.social · Aug 10

I know there's been a lot of talk about SSTs the next few days for #97L, but I think a lot of people are overlooking the Kelvin Wave (blue contours, right) that's going to pass overhead tomorrow & Tue.

Also, dry air shouldn't be an issue w/ a very large moisture envelope (left)

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webberweather.bsky.social @webberweather.bsky.social · Aug 10

Invest #97L has likely become a bonafide tropical cyclone this afternoon near the Cabo Verde Islands with a deep, consolidated, & persistent convective bursting pattern just after diurnal minimum.

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webberweather.bsky.social @webberweather.bsky.social · Aug 6

Hopefully, we keep the door shut on tropical cyclones developing/intensifying near the US East Coast as long as possible this hurricane season because this is bad lol.

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webberweather.bsky.social @webberweather.bsky.social · Aug 6

Lol is the Atlantic really about to fumble an MJO, Kelvin, and Equatorial Rossby Wave passage over Africa

misva.aeris-data.fr/products/syn...

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