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Optimal MJO path for cold: it isn't what many think


GaWx

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Folks,

 To best illustrate the findings of the MJO phase related research I've done over the last week or so (using the normalized 1,240 days of KATL Jan. mean temp, data since 1975), see the 1st attachment below as a pic is worth 1,000 words in this case. To summarize, the best place to be for cold in at least Jan. is within the COD anywhere from phase 6 all of the way around to phase 3. This portion of the COD has had temp.'s averaging between 2 and 6 F colder than normal. The coldest part of the COD is in phase 8 (asterisked) followed by phase 7, which actually is intuitive. What isn't intuitive is that each and every one of the 8 phases is 3-6 F colder when within the COD vs. outside of it!

 

 So, in Jan. it is best for cold to be in phases 7 and 8 (-4 to -6 in the COD and -1 to 0 outside the COD) and worst to be in phases 4-5 (+3 to +6 outside the COD and 0 to +1 inside the COD). Though not as good as 7-8, it is good to be within phases 6 as well as 1-3 when within the COD (-2 to -3).

 

 So, based on these findings, I drew an optimal path for cold in at least Jan. MJOwise (see 2nd attachment). Optimally, start around the cool phase 6 within the COD and slowly circle around counterclockwise within the COD through the cold phases 7-8 and then through the still chilly phases 1-3. This could easily take 2-3 weeks or so (the longer the better). By the way, ~1 in 3 Jan. days is in the COD. The chance of getting a 7+ day straight period in any one Jan. of COD phases not within phases 4-5 is ~3/8 (15 of 40 Jan's had this). I'll be hoping to see this later this month for the best chance for persistent cold chances over a 10+ day period. Model consensus is suggesting a decent shot at this for the 2nd half of this month fwiw. We'll see.

 

 The following are many of the closest examples I could find to the optimal path....note that all of them resulted in anywhere from a 10 to 19 day period of solid cold domination:

 

1. 1/10-28/1977: http://www.bom.gov.au/climate/mjo/graphics/archive/MJO_phase/197701.phase.90days.gif

 

2. 1/6-15/1988:

http://www.bom.gov.au/climate/mjo/graphics/archive/MJO_phase/198801.phase.90days.gif

 

3. 1/8-19/1994:

http://www.bom.gov.au/climate/mjo/graphics/archive/MJO_phase/199401.phase.90days.gif

 

4. 1/4-14/1996:

http://www.bom.gov.au/climate/mjo/graphics/archive/MJO_phase/199601.phase.90days.gif

 

5. 1/20-31/2000:

http://www.bom.gov.au/climate/mjo/graphics/archive/MJO_phase/200001.phase.90days.gif

 

6. 1/13-27/2003:

http://www.bom.gov.au/climate/mjo/graphics/archive/MJO_phase/200301.phase.90days.gif

 

7. 1/1-10/2014:

http://www.bom.gov.au/climate/mjo/graphics/archive/MJO_phase/201401.phase.90days.gif

 

 

Attach. #1: KATL normalized avg. temp. anomalies.JAN 1975-2014 by MJO phase: 8 and 7 within COD coldest followed by 1-3 within COD and then 6 within COD

post-882-0-91732700-1420242524_thumb.png

 

 

 

Attach.#2: optimal MJO path for 10-14+ days of lengthy cold dominated period

post-882-0-98505400-1420242779_thumb.gif

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Nice work! I love how the last image is just a C inside COD which could stand for....Cold! But seriously, good work. I see a lot of misunderstandings about the MJO and in reality it depends on where you are, I guess. For us I like the way it's headed on the GEFS (could end up going into 7 or 8 inside the COD as the ensemble inches that way)...phase 6 and 7 aren't bad at all, just getting out and staying out of 5 is what we need. We will see!

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1) Lol, thanks, Jon. I wasn't even thinking about that.

 

2) Folks,

 Regarding the 7 listed cold COD periods, note that a solid -NAO existed only in/near the 1977 and 1996 noted periods. The -AO wasn't persistently solidly negative in/near the 1988, 2000, and 2003 noted periods. In other words, the Pacific, alone, with the help of the favorable part of the COD MJO is fully capable of allowing for a lengthy solid cold period even without good -AO/-NAO type blocking.

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NChighcountry/NCsnow, thanks!

 

 My next subproject is to see if being just outside the COD in 7-8 has a strong tendency toward cold like being within the COD for 7-8. I'm going to look at least at amp.'s of 1-1.25 in Jan. I want to see if the main breakpoint is, indeed, ~1.0 (right near the circle) or else something a little outside the COD..

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  • 1 month later...

 MJO within/near the circle ftw for a long period of cold? It doesn't always work out but it seems to be in this case. The persistent cold got started 2/12. Well, it has been within/near the circle since 2/12.

 

 http://www.bom.gov.au/climate/mjo/graphics/rmm.phase.Last40days.gif

 

 Also, forecasts have it mainly staying within or near the circle for the rest of Feb. along with a very cold pattern.

 

 

See the 1st post in this thread for the ATL average temp. anomalies for Jan 1975-2014 by MJO phase and you'll see that within/near the circle has on average been a good bit colder than stronger amp MJO's.

 

 https://www.americanwx.com/bb/uploads/monthly_01_2015/post-882-0-91732700-1420242524.png

 

 It appears that the Jan research can be applied to Dec/Feb at least to a pretty good extent.

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