2023 Indicators (SST, SAL, MSLP, Wind shear, Steering, Instability) and Day 16+ Models

[ScottNAtlanta]

Ah yes, Tropical Storm Franklinose.

https://i.imgur.com/Y7bZ0px.png

Due to the sheer stupidity of the name, the name "Franklinose" was retired from the 2023 Atlantic hurricane season and will never be used again for another Atlantic hurricane.

Along with Josert

[Category5Kaiju]

https://www.ospo.noaa.gov/data/sst/contour/contour.small.gif

Don't just look at anomalies. I hear a lot of talk about how crazy warm the water is of equatorial S America. Five degree anomalies are only 22 C/23 C. If you look at the current SST map above, you see there is a ton more warmth in the Atlantic so it would be hard to maintain upward motion in the EPAC for very long at this point in the season

I think Derek Ortt pointed out something similar recently on Twitter. The warmest places in the Atlantic are simply much warmer than the EPAC, looking at raw sea surface temperatures.

[CyclonicFury]

Caribbean shear was actually BELOW average in August, despite the El Nino.


When you average out June-August as a whole, it comes out near to slightly below average.


So far, the model forecasts showing unusually low shear for an El Nino are verifying, which definitely is a factor for why this season has been so active despite El Nino conditions. Both the CFS and CanSIPS are predicting below average shear in the Caribbean/MDR for October and November, so it really makes me question if we'll see a standard Nino early shutdown this year. We've already seen 3 TCs form in or enter the Caribbean Sea this year, when some El Ninos have practically no Caribbean activity at all.

[weeniepatrol]

Surface pressures:



500mb RH:



Columnar precipitable water:

[weeniepatrol]

Monthly Tropical Weather Summary
NWS National Hurricane Center Miami FL
800 AM EDT Fri Sep 1 2023

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

Tropical cyclone activity in the Atlantic basin in August was above
normal overall in terms of the number of named storms, hurricanes,
and major hurricanes. In total, six named tropical cyclones formed
in the basin in August, with two of those becoming major hurricanes.
Based on a 30-year climatology (1991-2020), between 3-4 named storms
typically develop in August, with 1-2 of them becoming hurricanes. A
major hurricane typically forms in August every 1 to 2 years.

Franklin initially made landfall in the Dominican Republic as a
tropical storm, and later affected Bermuda with tropical storm
conditions as it passed by to the north as a hurricane. Harold made
landfall in south Texas as a tropical storm, and Idalia made
landfall in the Florida Big Bend region as a major hurricane.

In terms of Accumulated Cyclone Energy (ACE), which measures the
strength and duration of tropical storms and hurricanes, activity in
the basin so far in 2023 has been about 35 percent above average
compared to the long-term (1991-2020) mean.

[weeniepatrol]

It's stunning how every parameter you look at is so anomalously favorable, disregarding the El Nino. Factoring in? This may be unprecedented. IMHO, if the MJO does not constructively interfere with the El Nino standing wave in the second half of September and slow/shut things down, we are looking at another hyperactive season lol

[Steve]

It's stunning how every parameter you look at is so anomalously favorable, disregarding the El Nino. Factoring in? This may be unprecedented. IMHO, if the MJO does not constructively interfere with the El Nino standing wave in the second half of September and slow/shut things down, we are looking at another hyperactive season lol

https://www.cpc.ncep.noaa.gov/products/ ... jman.shtml

?

[weeniepatrol]

It's stunning how every parameter you look at is so anomalously favorable, disregarding the El Nino. Factoring in? This may be unprecedented. IMHO, if the MJO does not constructively interfere with the El Nino standing wave in the second half of September and slow/shut things down, we are looking at another hyperactive season lol

https://www.cpc.ncep.noaa.gov/products/ ... jman.shtml

?

Referring to this, particularly #4

[ScottNAtlanta]

Here is the link to dynamical MJO forecasts

https://www.cpc.ncep.noaa.gov/products/ ... r_wh.shtml

[WalterWhite]

GEFS and ECENS ensembles and the operational GFS generally show:

- Invest 94L developing into Tropical Storm Katia around September 3

- Another tropical wave coming from West Africa developing into Tropical Storm Lee around September 6, which could become a hurricane

- A subsequent tropical wave coming from West Africa developing into Tropical Storm Margot around September 9

I was a day early with Tropical Storm Katia.

[WalterWhite]

Interestingly, there has been no indication of a West African standing wave this August, nor has there been rising air over the Indian Ocean or the Maritime Continent. It is rather intriguing how this August was able to produce 6 storms despite the very unfavorable velocity potential patterns.

[Ntxw]

Interestingly, there has been no indication of a West African standing wave this August, nor has there been rising air over the Indian Ocean or the Maritime Continent. It is rather intriguing how this August was able to produce 6 storms despite the very unfavorable velocity potential patterns.

https://i.postimg.cc/GmDhvVvm/compday-ut-Jab-9-Dq-W.gif

Rising air occurred over the Africa-IO-MC window in the last quarter of August, at the same time activity picked up in the Atlantic as seen in the -VP anomalies. This is a favorable region for Atlantic activity as a whole. It will shift over to the IDL Pacific window the second half of September.

[Kingarabian]

Interestingly, there has been no indication of a West African standing wave this August, nor has there been rising air over the Indian Ocean or the Maritime Continent. It is rather intriguing how this August was able to produce 6 storms despite the very unfavorable velocity potential patterns.

https://i.postimg.cc/GmDhvVvm/compday-ut-Jab-9-Dq-W.gif

Rising motion usually always favors the region with the warmest SSTs. That's what's allowing Atlantic activity + a decoupled El Nino atmosphere.

[zzzh]

I'll just leave it here.

[WalterWhite]

Interestingly, there has been no indication of a West African standing wave this August, nor has there been rising air over the Indian Ocean or the Maritime Continent. It is rather intriguing how this August was able to produce 6 storms despite the very unfavorable velocity potential patterns.

https://i.postimg.cc/GmDhvVvm/compday-ut-Jab-9-Dq-W.gif

Rising air occurred over the Africa-IO-MC window in the last quarter of August, at the same time activity picked up in the Atlantic as seen in the -VP anomalies. This is a favorable region for Atlantic activity as a whole. It will shift over to the IDL Pacific window the second half of September.

https://i.imgur.com/wjfsJzN.png

What happened to the West African standing wave, though?

[Ntxw]

Interestingly, there has been no indication of a West African standing wave this August, nor has there been rising air over the Indian Ocean or the Maritime Continent. It is rather intriguing how this August was able to produce 6 storms despite the very unfavorable velocity potential patterns.

https://i.postimg.cc/GmDhvVvm/compday-ut-Jab-9-Dq-W.gif

Rising air occurred over the Africa-IO-MC window in the last quarter of August, at the same time activity picked up in the Atlantic as seen in the -VP anomalies. This is a favorable region for Atlantic activity as a whole. It will shift over to the IDL Pacific window the second half of September.

https://i.imgur.com/wjfsJzN.png

What happened to the West African standing wave, though?

It was neutral-ish until about mid month then became very favorable. Assuming things continue progress, sinking air will return.

[WalterWhite]

Rising air occurred over the Africa-IO-MC window in the last quarter of August, at the same time activity picked up in the Atlantic as seen in the -VP anomalies. This is a favorable region for Atlantic activity as a whole. It will shift over to the IDL Pacific window the second half of September.

https://i.imgur.com/wjfsJzN.png

What happened to the West African standing wave, though?

It was neutral-ish until about mid month then became very favorable. Assuming things continue progress, sinking air will return.

So why is rising air over West Africa not present this year, unlike 2018, 2019, 2020, 2021, and 2022? 2018 and 2019 were +ENSO years, yet they both had a West African standing wave.

[Ntxw]

What happened to the West African standing wave, though?

It was neutral-ish until about mid month then became very favorable. Assuming things continue progress, sinking air will return.

So why is rising air over West Africa not present this year, unlike 2018, 2019, 2020, 2021, and 2022? 2018 and 2019 were +ENSO years, yet they both had a West African standing wave.

There has not been an El Nino strong enough to pull the background forcing out of Africa-MC since 2015, in those years you noted. The La Nina and psuedo-weak Nino's allowed the very warm MC waters to dominate. There's a whole wide discussion about SSTs warming and influence but that gets too deep. Tropical forcing is all about Africa-IO-MC and WPAC-CPAC. The two couplets are influenced by ENSO and IOD quite a bit.

[WalterWhite]

It was neutral-ish until about mid month then became very favorable. Assuming things continue progress, sinking air will return.

So why is rising air over West Africa not present this year, unlike 2018, 2019, 2020, 2021, and 2022? 2018 and 2019 were +ENSO years, yet they both had a West African standing wave.

There has not been an El Nino strong enough to pull the background forcing out of Africa-MC since 2015, in those years you noted. The La Nina and psuedo-weak Nino's allowed the very warm MC waters to dominate. There's a whole wide discussion about SSTs warming and influence but that gets too deep. Tropical forcing is all about Africa-IO-MC and WPAC-CPAC. The two couplets are influenced by ENSO and IOD quite a bit.

https://i.imgur.com/0sazf7i.png

And even without this standing wave in West Africa, it is really puzzling that 2023 is (so far) following the same formula for tropical cyclone activity as seen in those years mentioned: ramping up activity in late August and September by spamming as many storms as possible in the hopes that some become hurricanes or major hurricanes. I always assumed this was a byproduct of the standing wave in West Africa, but is it not?

[Ntxw]

So why is rising air over West Africa not present this year, unlike 2018, 2019, 2020, 2021, and 2022? 2018 and 2019 were +ENSO years, yet they both had a West African standing wave.

There has not been an El Nino strong enough to pull the background forcing out of Africa-MC since 2015, in those years you noted. The La Nina and psuedo-weak Nino's allowed the very warm MC waters to dominate. There's a whole wide discussion about SSTs warming and influence but that gets too deep. Tropical forcing is all about Africa-IO-MC and WPAC-CPAC. The two couplets are influenced by ENSO and IOD quite a bit.

https://i.imgur.com/0sazf7i.png

And even without this standing wave in West Africa, it is really puzzling that 2023 is (so far) following the same formula for tropical cyclone activity as seen in those years mentioned: ramping up activity in late August and September by spamming as many storms as possible in the hopes that some become hurricanes or major hurricanes. I always assumed this was a byproduct of the standing wave in West Africa, but is it not?

It's not always an entire season type thing, there are periods of movement especially shorter time scales. I'm not versed enough for the longer time scales, but when there is passage even for short periods you can see an uptick. I would guess favorable seasons you would see it flare up and linger over longer.