Dead MJO effects on cyclone development for both Atl and EPA

[CaliforniaResident]

Seems like the WPAC is the only region that is still truly active. Even the EPAC has gotten quiet (I consider Hilda more of a WPAC storm due to it's location).

I was wondering what others on here think the dead MJO might bring. Maybe the EPAC won't get as many storms as predicted either and of course, it will make an already "dead" Atlantic season even "deader". It looks like MJO is expected to remain "dead" through September and by the time it comes back, it might be too late for hurricanes.

Do those of you who like to speculate revise your seasonal forecasts for the remainder of the season based on this dead MJO?

[Ntxw]

The MJO signal is often weakest during mature ENSO events (El Nino/La Nina) as the background state, convection across the Pacific during El Nino and IO/Atlantic/Indonesia during La Nina becomes dominant. I would not focus too much on the MJO when you have a significant ENSO event ongoing rather the base state.

[Yellow Evan]

MJO is usually dead during El Nino years.

[LarryWx]

TC Geneses 1995-2012: TC geneses per day (expressed as %) by MJO phase

August
1: 14%
2: 19%
3: 38%
4: 0%
5: 15%
6: 19%
7: 7%
8: 18%
Within Circle: 10% (one every 10 days)
ALL: 14%


September
1: 24%
2: 17%
3: 6%
4: 16%
5: 8%
6: 6%
7: 14%
8: 15%
Within Circle: 21% (one every five days)
ALL: 16%

October
1: 14%
2: 11%
3: 11%
4: 19%
5: 9%
6: 4%
7: 5%
8: 2%
Within Circle: 10% (one every ten days)
ALL: 10%

What does this show? Whereas being within the circle ("dead" MJO) has been associated with lower than average Aug. genesis rates within Aug. (10% or one every ten days vs 14% for all phases), Sep. is a whole other ballgame with it at a whopping 21% (one every five days vs 16% for all phases). Oct. falls back to average for the month (10% vs 10%)

[LarryWx]

TC Geneses 1995-2012: TC geneses per day (expressed as %) by MJO phase

August
1: 14%
2: 19%
3: 38%
4: 0%
5: 15%
6: 19%
7: 7%
8: 18%
Within Circle: 10% (one every 10 days)
ALL: 14%


September
1: 24%
2: 17%
3: 6%
4: 16%
5: 8%
6: 6%
7: 14%
8: 15%
Within Circle: 21% (one every five days)
ALL: 16%

October
1: 14%
2: 11%
3: 11%
4: 19%
5: 9%
6: 4%
7: 5%
8: 2%
Within Circle: 10% (one every ten days)
ALL: 10%

What does this show? Whereas being within the circle ("dead" MJO) has been associated with lower than average Aug. genesis rates within Aug. (10% or one every ten days vs 14% for all phases), Sep. is a whole other ballgame with it at a whopping 21% (one every five days vs 16% for all phases). Oct. falls back to average for the month (10% vs 10%)

Bump.
Most MJO projections keep the MJO within the circle at least well into the first half of Sep. As noted above, that's relatively favorable for geneses. That's especially the case for the strongest El Nino's as of Sep.:

For just the four Ninos since 1976 that were +1.0+ in Nno 3.4 in Sep. (1982, 1987, 1997, and 2002), a whopping 14 of the 15 Sep TC geneses (for those that later became TS+ strength) were when the MJO was within the circle:

1982: Chris, Debby, Ernesto
1987: Cindy, Dennis (but not Emily)
1997: Erika
2002: Edouard, Fay, Gustav, Hanna, Isidore, Josephine, Kyle, Lili

- There were 78 days within the circle during those 120 days...so, one Sep genesis every 6 days when within the circle for these four strongest Nino Sep.'s.
- There were 42 days outside the circle during those 120 days..so only the one genesis during those 42 days (Emily during phase 2) for these four strongest Nino Sep.'s.

Conclusion: Since the Sep. 2015 Nino 3.4 anomaly will be +1.0+, the most favorable conditions for genesis during this Sep. may very well be when within the circle. The hard stats since 1976 at least suggest that. So, the projection of within the circle MJO should, if anything, be viewed as more of a favorable factor than an unfavorable factor. Let's see what actually happens.

Edit: I continue to think that the best chance for a CONUS H landfall or two will be between mid Sep and early Oct based on past 2nd year strong El Niño seasons. The highest threat may very well be at or near the NE GOM coast (FL panhandle and nearby area) as per these seasons.

[LarryWx]

The MJO is forecasted to to be weak for the foreseeable future. It was briefly a little outside of the circle. However, it is either now back inside it or about to get there. Keep in mind that based on prior within the circle periods when the Sep Niño 3.4 anomaly was over +1.0 (like now), Atlantic basin tropical geneses have tended to be relatively frequent during Sep, especially for a strengthening toward strong Niño (see above in this thread for relevant stats, if interested). The bottom line as I see it is that I don't see the projected MJO as being a hindrance to later genesis and, if anything, I see it as somewhat favorable for Sep.

(Interestingly, Grace actually formed when the MJO was either in or near phase 1, which when looking at ALL seasons together since 1975 has had the highest Sep genesis frequency. For ALL seasons together, within the circle is 2nd.)