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

[TheStormExpert]

:uarrow: 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.

https://i.imgur.com/afMFWc5.gif
https://i.imgur.com/wuk6lHb.gif

2008 we also saw something similar happen.

https://i.imgur.com/ViWznQR.gif
https://i.imgur.com/d5oNP72.gif

Yeah the trough is what allowed Charley to take it’s unusual path for mid-August before the ridge shoved both Frances and Jeanne into Sewall's Point and Ivan into the Florida/Alabama Gulf Coast.

Btw, do you have the link to graphs like these?

[NDG]

:uarrow: 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.

https://i.imgur.com/afMFWc5.gif
https://i.imgur.com/wuk6lHb.gif

2008 we also saw something similar happen.

https://i.imgur.com/ViWznQR.gif
https://i.imgur.com/d5oNP72.gif

Yeah the trough is what allowed Charley to take it’s unusual path for mid-August before the ridge shoved both Frances and Jeanne into Sewall's Point and Ivan into the Florida/Alabama Gulf Coast.

Btw, do you have the link to graphs like these?

Then in '08 the pattern changed right in the middle of TS Fay, the reason why it nearly stalled across east central FL as it started feeling the ridging building to its north as the pattern changed.

You can get the graphics here:

https://psl.noaa.gov/cgi-bin/data/compo ... intpage.pl

[Shell Mound]

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?

I think these factors are important to consider. If ignored, some forecasts may bust. (I’m not changing mine at this time, but positing some “complications.”) ASO of 2019 had essentially the same ENSO and WAM/AEJ that is widely expected to be in place at the same time in 2020: cool neutral conditions in NINO 3 coupled with robust -VP centred over Africa and the western Indian Ocean. Yet these favourable indicators could not overcome the +IOD and resulting strong TUTT/sinking air over the tropical Atlantic during peak season, especially the month of October. (Also, ASO of 2019 featured a pronounced warm pool off New England and a +PMM north of the equator, similar to what we see this year.) If 2019 was so similar to 2020, then we need to examine factors that could derail current forecasts.

[toad strangler]

Tropical seasons are like snowflakes. Not one will ever be the same even in the same conditions.

[Shell Mound]

The July CFSv2 run, for what it’s worth, has made a rather dramatic shift in its outlook for the rising branch come ASO. Whereas previous runs showed Africa and the IO dominating, the new July run shows the MC taking over in time for the peak of the hurricane season. It also shows a much warmer +AMO signature during the peak of the season, along with an even wetter MDR/Caribbean, with less suppression of the ITCZ, owing to a -NAO trend during ASO vs. previous runs. If this were to transpire, we would likely see an even more active season, but the Bermuda High being weaker might lead to more OTS tracks, depending on where the storms tend to form. An -NAO during peak season, incidentally, would favour either a) OTS or b) tracks through the Caribbean/islands and into the Gulf, à la Allen ‘80, Ivan ‘04, or even Rita ‘05. Neutral to slightly positive NAO tends to favour the FL peninsula, while strongly +NAO tends to favour the Carolinas northward. -NAO favours either OTS and/or Caribbean/Gulf. The problem with the latest CFSv2 run is that it still shows a +PMM, so even with rising air centred over the MC and Caribbean/western MDR, some residual outflow from convection in the EPAC could induce bouts of shear from time to time. Basically, the latest CFSv2 setup for ASO is as follows: cool neutral ENSO or weak west-based (Modoki) Niña, rising branch over MC instead of Africa/IO, +PMM, -NAO, +AMO, neutral to slightly negative PDO.

[chaser1]

The July CFSv2 run, for what it’s worth, has made a rather dramatic shift in its outlook for the rising branch come ASO. Whereas previous runs showed Africa and the IO dominating, the new July run shows the MC taking over in time for the peak of the hurricane season. It also shows a much warmer +AMO signature during the peak of the season, along with an even wetter MDR/Caribbean, with less suppression of the ITCZ, owing to a -NAO trend during ASO vs. previous runs. If this were to transpire, we would likely see an even more active season, but the Bermuda High being weaker might lead to more OTS tracks, depending on where the storms tend to form. An -NAO during peak season, incidentally, would favour either a) OTS or b) tracks through the Caribbean/islands and into the Gulf, à la Allen ‘80, Ivan ‘04, or even Rita ‘05. Neutral to slightly positive NAO tends to favour the FL peninsula, while strongly +NAO tends to favour the Carolinas northward. -NAO favours either OTS and/or Caribbean/Gulf. The problem with the latest CFSv2 run is that it still shows a +PMM, so even with rising air centred over the MC and Caribbean/western MDR, some residual outflow from convection in the EPAC could induce bouts of shear from time to time. Basically, the latest CFSv2 setup for ASO is as follows: cool neutral ENSO or weak west-based (Modoki) Niña, rising branch over MC instead of Africa/IO, +PMM, -NAO, +AMO, neutral to slightly negative PDO.

https://www.tropicaltidbits.com/analysis/models/cfs-mon/2020070118/cfs-mon_01_chi200Mean_month_global_1.png

Ever feel like you've mentally run around a round race track over and over and over again, just to wind up right where you started? For our particular group of tropical weather enthusiasts, I'd call that feeling "Paralysis by Analysis" Don't get me wrong, this IS exactly the correct forum for tropical cyclone development indicators but new model and data updates are constantly coming out and the "needle" just doesn't move all that much following any one crumb or morsel in particular. Sure, perhaps an eyebrow raise by Spock maybe but an overall abrupt reanalysis? As I see it, it's not that much different from the Nino/Nina or the SST death-watch. Incremental "it's up", "it's down", "it's deep", "it's shallow" or one or two weeks worth of anomalies eventually starts feeling like watching grass grow. Observations are worth noting, but I probably wouldn't base a thesis on each one of them.

[CyclonicFury]

Tropical seasons are like snowflakes. Not one will ever be the same even in the same conditions.

Great point! That's why you should never expect a "2005 repeat" or a "2013 repeat." EVERY season is different!

[Hammy]

That CFS chart has to be the most unfavorable setup I've seen in awhile.

[CyclonicFury]

The CFS charts on Tidbits always seem to change whenever the month changes, I'm not sure why that is.

[aspen]

:uarrow: That CFS chart has to be the most unfavorable setup I've seen in awhile.

It’s the exact opposite of what all the other models have been showing

[TheStormExpert]

The July CFSv2 run, for what it’s worth, has made a rather dramatic shift in its outlook for the rising branch come ASO. Whereas previous runs showed Africa and the IO dominating, the new July run shows the MC taking over in time for the peak of the hurricane season. It also shows a much warmer +AMO signature during the peak of the season, along with an even wetter MDR/Caribbean, with less suppression of the ITCZ, owing to a -NAO trend during ASO vs. previous runs. If this were to transpire, we would likely see an even more active season, but the Bermuda High being weaker might lead to more OTS tracks, depending on where the storms tend to form. An -NAO during peak season, incidentally, would favour either a) OTS or b) tracks through the Caribbean/islands and into the Gulf, à la Allen ‘80, Ivan ‘04, or even Rita ‘05. Neutral to slightly positive NAO tends to favour the FL peninsula, while strongly +NAO tends to favour the Carolinas northward. -NAO favours either OTS and/or Caribbean/Gulf. The problem with the latest CFSv2 run is that it still shows a +PMM, so even with rising air centred over the MC and Caribbean/western MDR, some residual outflow from convection in the EPAC could induce bouts of shear from time to time. Basically, the latest CFSv2 setup for ASO is as follows: cool neutral ENSO or weak west-based (Modoki) Niña, rising branch over MC instead of Africa/IO, +PMM, -NAO, +AMO, neutral to slightly negative PDO.

https://www.tropicaltidbits.com/analysis/models/cfs-mon/2020070118/cfs-mon_01_chi200Mean_month_global_1.png

Definitely not a favorable setup for the Atlantic. Wouldn’t surprise me to see forecasters back off on their bullish numbers this month or next if trends and other models join in.

[CyclonicFury]

This is an old thread from 2017, but suggests CFS changes model climatology when the month changes.
https://twitter.com/TropicalTidbits/sta ... 5335771136

[Kingarabian]

:uarrow: That CFS chart has to be the most unfavorable setup I've seen in awhile.

It's actually pretty favorable.

[Hammy]

:uarrow: That CFS chart has to be the most unfavorable setup I've seen in awhile.

It's actually pretty favorable.

Wouldn't the sinking air result in wave suppression over Africa and more shear over the eastern Atlantic, or am I misinterpreting? They're still relatively new to me.

[TheStormExpert]

Disregard what I said I guess.

[Kingarabian]

:uarrow: That CFS chart has to be the most unfavorable setup I've seen in awhile.

It's actually pretty favorable.

Wouldn't the sinking air result in wave suppression over Africa and more shear over the eastern Atlantic, or am I misinterpreting? They're still relatively new to me.

There will still be plenty of waves. The +VP200 anomaly concentration over the Atlantic is pretty minor compared to what we've seen in some years that still had above average activity. This is pretty classic La Nina atmospheric setup by the CFS. The EPAC will likely be shutdown while the MDR and especially the Caribbean look wide open.

But then again this is the CFS and it's really banking on the La Nina taking off.The Euro doesn't show this setup going into August. Regardless, both of their scenarios favor an active Atlantic hurricane season.

[Hammy]

It's actually pretty favorable.

Wouldn't the sinking air result in wave suppression over Africa and more shear over the eastern Atlantic, or am I misinterpreting? They're still relatively new to me.

There will still be plenty of waves. The +VP200 anomaly concentration over the Atlantic is pretty minor compared to what we've seen in some years that still had above average activity. This is pretty classic La Nina atmospheric setup by the CFS. The EPAC will likely be shutdown while the MDR and especially the Caribbean look wide open.

But then again this is the CFS and it's really banking on the La Nina taking off.The Euro doesn't show this setup going into August. Regardless, both of their scenarios favor an active Atlantic hurricane season.

Was the +VP200 anomaly being over the tropical Atlantic, rather than Africa, what was most suppressing development and strengthening over the last few years?

[Kingarabian]

Wouldn't the sinking air result in wave suppression over Africa and more shear over the eastern Atlantic, or am I misinterpreting? They're still relatively new to me.

There will still be plenty of waves. The +VP200 anomaly concentration over the Atlantic is pretty minor compared to what we've seen in some years that still had above average activity. This is pretty classic La Nina atmospheric setup by the CFS. The EPAC will likely be shutdown while the MDR and especially the Caribbean look wide open.

But then again this is the CFS and it's really banking on the La Nina taking off.The Euro doesn't show this setup going into August. Regardless, both of their scenarios favor an active Atlantic hurricane season.

Was the +VP200 anomaly being over the tropical Atlantic, rather than Africa, what was most suppressing development and strengthening over the last few years?

Very likely the EPAC being very active coupled with +ENSO enhancing shear across the Caribbean. These two key variables will very likely not be present this season.

[TheStormExpert]

It's actually pretty favorable.

Wouldn't the sinking air result in wave suppression over Africa and more shear over the eastern Atlantic, or am I misinterpreting? They're still relatively new to me.

There will still be plenty of waves. The +VP200 anomaly concentration over the Atlantic is pretty minor compared to what we've seen in some years that still had above average activity. This is pretty classic La Nina atmospheric setup by the CFS. The EPAC will likely be shutdown while the MDR and especially the Caribbean look wide open.

But then again this is the CFS and it's really banking on the La Nina taking off.The Euro doesn't show this setup going into August. Regardless, both of their scenarios favor an active Atlantic hurricane season.

Then again it’s the same Euro which showed this unfavorable setup the last 3-4 seasons, and yet we saw monsters such as Matthew, Harvey, Irma, Maria, Michael, Dorian, and Lorenzo.

[TheStormExpert]

Strong Wave about to splashdown off the west coast of Africa.

 https://twitter.com/thestevecop/status/1278806451478245377