2020 Indicators: SST's / SAL / MSLP / Steering / Shear / Instability / Sat Images

[WeatherEmperor]

I have a question that I hope somebody can help with. The last few days the NAO has been persistently negative yet we have seen stronger east coast ridging causing record high temperatures in south florida and reduced rain precipitation chances. If the NAO is mostly negative, shouldnt we be seeing more troughing? It looks like there is quite a bit more to the ridge/trough setups than just a positive or negative NAO. What other factors could be in play?




Sent from my iPhone using Tapatalk

[Siker]

I have a question that I hope somebody can help with. The last few days the NAO has been persistently negative yet we have seen stronger east coast ridging causing record high temperatures in south florida and reduced rain precipitation chances. If the NAO is mostly negative, shouldnt we be seeing more troughing? It looks like there is quite a bit more to the ridge/trough setups than just a positive or negative NAO. What other factors could be in play?

While Florida has been under a ridge centered over Florida / the Gulf of Mexico the past few days, the Northeast US has been under a trough during that same time period. I don't know the exact formula of the NAO index, but there's been a good bit of ridging over Canada and Greenland during that same time, which corresponds with my memory of a -NAO.

[Shell Mound]

There is some debate over the connection between IOD and ENSO, but essentially the +/- mode of the IOD can hinder or propel atmospheric changes during ENSO transitions. For instance, a + IOD increases Pacific trade winds, promotes La Nina, and strengthens the Walker circulation. A - IOD creates weaker trade winds, promotes El Nino, and weakens the Walker circulation. So basically the chain is:

positive IOD --> cooling ENSO (La Nina) --> enhanced Walker circulation --> more active Atlantic
negative IOD --> warming ENSO (El Nino) --> weakened Walker circulation --> less active Atlantic

I thought it was the other way around, doesn't a -IOD favor upward motion over the Maritime Continent, which is more La Niña like, while a +IOD favors sinking over this region?

Eventually it does, but there's essentially a cycle it must complete:
https://i.imgur.com/ASGnNYD.png

Compare circulations here as well:
https://i.imgur.com/d6iJJlF.png

https://i.imgur.com/5QIkooh.png
https://i.imgur.com/iHJSneL.png

Again want to iterate the beginning of my post, there is some debate over the connection between IOD and ENSO. Research on the IOD is still in its infancy so to speak (discovered about ~25 years ago). Its true connection is still unknown, but this research article (https://commons.lib.niu.edu/bitstream/1 ... _12302.pdf) does a good job of describing the different teleconnections.

According to this preliminary thesis, there definitely appears to be a strong link between the IOD and the persistence of the TUTT (anticyclonic wave break / PV streamer) over portions of the Atlantic basin. An +IOD tends to be correlated with a persistent TUTT and thus enhanced vertical wind shear over portions of the MDR and/or Caribbean, which often tends to offset the otherwise favourable impact of the rising branch (-VP) being centred over Africa and the western IO. The stronger TUTT also promotes more subsidence over the basin. According to the paper, ASO of 2019 featured a strongly +IOD, especially in October, which served to inhibit overall activity in the deep tropics, despite cool neutral SSTs in NINO 3 (per NCEP/NCAR reanalysis) and the enhanced WAM/AEJ being similar to current estimates and projections in 2020. A robust warm pool over the subtropical Northwestern Atlantic might reinforce the TUTT as well. Some excerpts from the publication:

The (positive — ed.) IOD produced an El Niño-like teleconnection pattern observed through 200-hPa velocity potential anomalies. In the subtropical Atlantic, above-average sea surface temperatures persisted for much of the season, which may have contributed to increased activity at higher latitudes. ... Given that the record positive IOD occurred ... with ENSO-neutral conditions, it likely helped to concentrate upward motion over Africa and the western Indian Ocean (as is projected for 2020 — ed.) while simultaneously suppressing upward motion over the tropical Atlantic.

 https://twitter.com/TARCweather/status/1278079030072414211



 https://twitter.com/antmasiello/status/1276241624553619456



 https://twitter.com/AndyHazelton/status/1277960215061651456



 https://twitter.com/MJVentrice/status/1277973778933243905



 https://twitter.com/webberweather/status/1278082384102031361



 https://twitter.com/webberweather/status/1278364399095480320

[AutoPenalti]

El niño conditions could be possible if that were to verify, the Atlantic would pretty much be suppressed for the duration of the season, but so far that seems to be the opposite of what’s happening right now.

[SFLcane]

I have a question that I hope somebody can help with. The last few days the NAO has been persistently negative yet we have seen stronger east coast ridging causing record high temperatures in south florida and reduced rain precipitation chances. If the NAO is mostly negative, shouldnt we be seeing more troughing? It looks like there is quite a bit more to the ridge/trough setups than just a positive or negative NAO. What other factors could be in play?

https://uploads.tapatalk-cdn.com/20200701/2102f5279d08f2ef73f349c3a5ff44ec.gif


Sent from my iPhone using Tapatalk

NAO is part of it but AO can play a role too. Trof coming

[NDG]

I have a question that I hope somebody can help with. The last few days the NAO has been persistently negative yet we have seen stronger east coast ridging causing record high temperatures in south florida and reduced rain precipitation chances. If the NAO is mostly negative, shouldnt we be seeing more troughing? It looks like there is quite a bit more to the ridge/trough setups than just a positive or negative NAO. What other factors could be in play?

While Florida has been under a ridge centered over Florida / the Gulf of Mexico the past few days, the Northeast US has been under a trough during that same time period. I don't know the exact formula of the NAO index, but there's been a good bit of ridging over Canada and Greenland during that same time, which corresponds with my memory of a -NAO.

Definitely not the typical -NAO during the past 10 days or so since it turned negative with ridging remaining in SE Canada.

[TheStormExpert]

I have a question that I hope somebody can help with. The last few days the NAO has been persistently negative yet we have seen stronger east coast ridging causing record high temperatures in south florida and reduced rain precipitation chances. If the NAO is mostly negative, shouldnt we be seeing more troughing? It looks like there is quite a bit more to the ridge/trough setups than just a positive or negative NAO. What other factors could be in play?

While Florida has been under a ridge centered over Florida / the Gulf of Mexico the past few days, the Northeast US has been under a trough during that same time period. I don't know the exact formula of the NAO index, but there's been a good bit of ridging over Canada and Greenland during that same time, which corresponds with my memory of a -NAO.

Definitely not the typical -NAO during the past 10 days or so since it turned negative with ridging remaining in SE Canada.

https://i.imgur.com/ifii3Oh.gif

Definitely would shove anything coming out of the Tropical Atlantic towards the Carolinas or NE U.S.

[TheStormExpert]

 https://twitter.com/weathergarrett/status/1278338533900652547

[aspen]

:eek:

https://twitter.com/weathergarrett/status/1278338533900652547

32 C off the Gulf coast of Florida! I don’t think I’ve ever seen SSTs get that high in the Atlantic before.

[TheStormExpert]

:eek:

https://twitter.com/weathergarrett/status/1278338533900652547

32 C off the Gulf coast of Florida! I don’t think I’ve ever seen SSTs get that high in the Atlantic before.

Yeah that's nearly off the chart! HOPEFULLY nothing pops up to take advantage of these SST's cause Florida could be in BIG TROUBLE if so.

[Shell Mound]

I thought it was the other way around, doesn't a -IOD favor upward motion over the Maritime Continent, which is more La Niña like, while a +IOD favors sinking over this region?

Eventually it does, but there's essentially a cycle it must complete:
https://i.imgur.com/ASGnNYD.png

Compare circulations here as well:
https://i.imgur.com/d6iJJlF.png

https://i.imgur.com/5QIkooh.png
https://i.imgur.com/iHJSneL.png

Again want to iterate the beginning of my post, there is some debate over the connection between IOD and ENSO. Research on the IOD is still in its infancy so to speak (discovered about ~25 years ago). Its true connection is still unknown, but this research article (https://commons.lib.niu.edu/bitstream/1 ... _12302.pdf) does a good job of describing the different teleconnections.

According to this preliminary thesis, there definitely appears to be a strong link between the IOD and the persistence of the TUTT (anticyclonic wave break / PV streamer) over portions of the Atlantic basin. An +IOD tends to be correlated with a persistent TUTT and thus enhanced vertical wind shear over portions of the MDR and/or Caribbean, which often tends to offset the otherwise favourable impact of the rising branch (-VP) being centred over Africa and the western IO. The stronger TUTT also promotes more subsidence over the basin. According to the paper, ASO of 2019 featured a strongly +IOD, especially in October, which served to inhibit overall activity in the deep tropics, despite cool neutral SSTs in NINO 3 (per NCEP/NCAR reanalysis) and the enhanced WAM/AEJ being similar to current estimates and projections in 2020. A robust warm pool over the subtropical Northwestern Atlantic might reinforce the TUTT as well. Some excerpts from the publication:

The (positive — ed.) IOD produced an El Niño-like teleconnection pattern observed through 200-hPa velocity potential anomalies. In the subtropical Atlantic, above-average sea surface temperatures persisted for much of the season, which may have contributed to increased activity at higher latitudes. ... Given that the record positive IOD occurred ... with ENSO-neutral conditions, it likely helped to concentrate upward motion over Africa and the western Indian Ocean (as is projected for 2020 — ed.) while simultaneously suppressing upward motion over the tropical Atlantic.

https://twitter.com/TARCweather/status/1278079030072414211
https://twitter.com/antmasiello/status/1276241624553619456
https://twitter.com/AndyHazelton/status/1277960215061651456
https://twitter.com/MJVentrice/status/1277973778933243905
https://twitter.com/webberweather/status/1278082384102031361
https://twitter.com/webberweather/status/1278364399095480320

USTropics, CyclonicFury, and Kingarabian, what are your thoughts on this?

[toad strangler]

 http://twitter.com/TylerJStanfield/status/1278417098746867719

[CyclonicFury]

Eventually it does, but there's essentially a cycle it must complete:
https://i.imgur.com/ASGnNYD.png

Compare circulations here as well:
https://i.imgur.com/d6iJJlF.png

https://i.imgur.com/5QIkooh.png
https://i.imgur.com/iHJSneL.png

Again want to iterate the beginning of my post, there is some debate over the connection between IOD and ENSO. Research on the IOD is still in its infancy so to speak (discovered about ~25 years ago). Its true connection is still unknown, but this research article (https://commons.lib.niu.edu/bitstream/1 ... _12302.pdf) does a good job of describing the different teleconnections.

According to this preliminary thesis, there definitely appears to be a strong link between the IOD and the persistence of the TUTT (anticyclonic wave break / PV streamer) over portions of the Atlantic basin. An +IOD tends to be correlated with a persistent TUTT and thus enhanced vertical wind shear over portions of the MDR and/or Caribbean, which often tends to offset the otherwise favourable impact of the rising branch (-VP) being centred over Africa and the western IO. The stronger TUTT also promotes more subsidence over the basin. According to the paper, ASO of 2019 featured a strongly +IOD, especially in October, which served to inhibit overall activity in the deep tropics, despite cool neutral SSTs in NINO 3 (per NCEP/NCAR reanalysis) and the enhanced WAM/AEJ being similar to current estimates and projections in 2020. A robust warm pool over the subtropical Northwestern Atlantic might reinforce the TUTT as well. Some excerpts from the publication:

The (positive — ed.) IOD produced an El Niño-like teleconnection pattern observed through 200-hPa velocity potential anomalies. In the subtropical Atlantic, above-average sea surface temperatures persisted for much of the season, which may have contributed to increased activity at higher latitudes. ... Given that the record positive IOD occurred ... with ENSO-neutral conditions, it likely helped to concentrate upward motion over Africa and the western Indian Ocean (as is projected for 2020 — ed.) while simultaneously suppressing upward motion over the tropical Atlantic.

https://twitter.com/TARCweather/status/1278079030072414211
https://twitter.com/antmasiello/status/1276241624553619456
https://twitter.com/AndyHazelton/status/1277960215061651456
https://twitter.com/MJVentrice/status/1277973778933243905
https://twitter.com/webberweather/status/1278082384102031361
https://twitter.com/webberweather/status/1278364399095480320

USTropics, CyclonicFury, and Kingarabian, what are your thoughts on this?

Realistically I expect the IOD to remain neutral during peak of the season. We likely won't see a legitimate -IOD, but I don't see a strong +IOD like 2019. The TUTT strength is difficult to forecast in the long range (and the CanSIPS has very low shear in the deep tropics for ASO).

[toad strangler]

 http://twitter.com/hurricanetrack/status/1278415257162207239

[Shell Mound]

According to this preliminary thesis, there definitely appears to be a strong link between the IOD and the persistence of the TUTT (anticyclonic wave break / PV streamer) over portions of the Atlantic basin. An +IOD tends to be correlated with a persistent TUTT and thus enhanced vertical wind shear over portions of the MDR and/or Caribbean, which often tends to offset the otherwise favourable impact of the rising branch (-VP) being centred over Africa and the western IO. The stronger TUTT also promotes more subsidence over the basin. According to the paper, ASO of 2019 featured a strongly +IOD, especially in October, which served to inhibit overall activity in the deep tropics, despite cool neutral SSTs in NINO 3 (per NCEP/NCAR reanalysis) and the enhanced WAM/AEJ being similar to current estimates and projections in 2020. A robust warm pool over the subtropical Northwestern Atlantic might reinforce the TUTT as well. Some excerpts from the publication:


https://twitter.com/TARCweather/status/1278079030072414211
https://twitter.com/antmasiello/status/1276241624553619456
https://twitter.com/AndyHazelton/status/1277960215061651456
https://twitter.com/MJVentrice/status/1277973778933243905
https://twitter.com/webberweather/status/1278082384102031361
https://twitter.com/webberweather/status/1278364399095480320

USTropics, CyclonicFury, and Kingarabian, what are your thoughts on this?

Realistically I expect the IOD to remain neutral during peak of the season. We likely won't see a legitimate -IOD, but I don't see a strong +IOD like 2019. The TUTT strength is difficult to forecast in the long range (and the CanSIPS has very low shear in the deep tropics for ASO).

Isn’t the CanSIPS less reliable than the UKMET, ECMWF, and CFSv2 at this range?

[toad strangler]

For reference ... JULY



 http://twitter.com/philklotzbach/status/1278395948675280896

[TheStormExpert]

USTropics, CyclonicFury, and Kingarabian, what are your thoughts on this?

Realistically I expect the IOD to remain neutral during peak of the season. We likely won't see a legitimate -IOD, but I don't see a strong +IOD like 2019. The TUTT strength is difficult to forecast in the long range (and the CanSIPS has very low shear in the deep tropics for ASO).

Isn’t the CanSIPS less reliable than the UKMET, ECMWF, and CFSv2 at this range?

You’d think so considering it’s the Canadian model.

[Hammy]

Realistically I expect the IOD to remain neutral during peak of the season. We likely won't see a legitimate -IOD, but I don't see a strong +IOD like 2019. The TUTT strength is difficult to forecast in the long range (and the CanSIPS has very low shear in the deep tropics for ASO).

Isn’t the CanSIPS less reliable than the UKMET, ECMWF, and CFSv2 at this range?

You’d think so considering it’s the Canadian model.

It's been performing decently since being upgraded last year.

[storminabox]

I have a question that I hope somebody can help with. The last few days the NAO has been persistently negative yet we have seen stronger east coast ridging causing record high temperatures in south florida and reduced rain precipitation chances. If the NAO is mostly negative, shouldnt we be seeing more troughing? It looks like there is quite a bit more to the ridge/trough setups than just a positive or negative NAO. What other factors could be in play?

https://uploads.tapatalk-cdn.com/20200701/2102f5279d08f2ef73f349c3a5ff44ec.gif


Sent from my iPhone using Tapatalk

Also -NAO in the summer often has a very different effect than it would in say the winter/spring

[NDG]

I will never forget is 2004, fairly persistent troughiness over the Great Lakes from June through August to later disappear during the peak of the season.




2008 we also saw something similar happen.