EPAC Tropical Action 2011

[HurricaneJosh]

Who, from PSU "told" JoePa he didn't have authority?

I just thought I'd get this thread going.

The EPAC is one of my favorite basins. As a cyclone chaser from Southern California, I sometimes think of the EPAC as "MBY"-- and since no one else is that into it, I feel like it belongs to me personally. (Well... Me and Jorge, maybe. )

So... What kind of season are we looking at? The later part of the EPAC season is usually more interesting-- most of the intense landfalls happen in October, when the cyclones start recurving toward the MX coast rather than fishing. If we switch to El Nino late-season, will that maybe augment the October magic on this side?

[gil888]

Agony alert! LOL You still got 6 weeks... and I'd bet on a cruddy EPac season unless El Nino comes on unexpectedly...

[HurricaneJosh]

Agony alert! LOL You still got 6 weeks... and I'd bet on a cruddy EPac season unless El Nino comes on unexpectedly...

Hey, at heart I'm still a NATL dude, so it's not like I'm rooting for an El Nino. I look at the EPAC as an insurance policy-- kind of like a backup plan-- for crappy NATL years.

[HurricaneJosh]

It's hot in L.A. today-- getting up to the 90s-- so it kind of made me feel like it's time to start this thread. I can feel the seasonal change in the air.

[Supercane]

Agony alert! LOL You still got 6 weeks... and I'd bet on a cruddy EPac season unless El Nino comes on unexpectedly...

I usually agree with you on ENSO, but have to disagree here -- I think an El Niño by fall is becoming increasingly likely. So I'd bank on a fun EPAC season.

[k***]

nino and pacific in general ftw

[Ed Lizard]

nino and pacific in general ftw

16 years in. Warm AMO has to be almost over, and then you'll be as happy as a little girl getting a pony for Christmas.

[HurricaneJosh]

16 years in. Warm AMO has to be almost over, and then you'll be as happy as a little girl getting a pony for Christmas.

Not really. These phases can last several decades. We could be only in the middle of it.

[Ed Lizard]

Gilbert, Hugo and Andrew show a switch back to a cool AMO (and I always heard they ran on average 20 years), numbers may be down, but there will be some quality storms in some seasons.

[k***]

Not really. These phases can last several decades. We could be only in the middle of it.

I don't think anyone really knows. I hope we can squeeze another 15 years out of it and get another one right before we die.

[HurricaneJosh]

I don't think anyone really knows.

Agreed-- which is why I think it's silly to suggest it's ending simply because we're 16 years in.

I hope we can squeeze another 15 years out of it and get another one right before we die.

Bingo. I want this one to continue during my prime chase years.

[Ed Lizard]

Agreed-- which is why I think it's silly to suggest it's ending simply because we're 16 years in.

Bingo. I want this one to continue during my prime chase years.

You wouldn't have chased Andrew and Gilbert?

[HurricaneJosh]

You wouldn't have chased Andrew and Gilbert?

Oh, of course I would have. But I was a college kid back then-- didn't have the time or the resources.

[Ed Lizard]

I may have been off slightly. I know I heard 20 years, I know it, but...

[gil888]

I usually agree with you on ENSO, but have to disagree here -- I think an El Niño by fall is becoming increasingly likely. So I'd bank on a fun EPAC season.

So why is El Nino becoming increasingly likely?

[HurricaneJosh]

ENSO fight!!1!

[wxmx]

So why is El Nino becoming increasingly likely?

There's a distinct weakening of the La Niña event, no doubt, but I see little evidence of any Niño emergence. Atmosphere is fully Niña mode right now (up and down flow), with little evidence of eastward propagating KWs/WWBs. As you have already noted, there's some incipient WWB event, but models keep it from getting to the dateline, not enough to say we are going El Niño soon.

[Supercane]

So why is El Nino becoming increasingly likely?

The MJO is forecast by nearly all the models to progress through phases 6-8 over the next week or so with an amplitude well over 1. If such a progression materializes, the enhanced convection will shift into the western and central Pacific, as illustrated in the ensemble GFS OLR forecast (note the similarity between the forecast and the major WWB in January). This will help further warm the SSTAs.

Moreover, negative subsurface T anomalies under the equatorial Pacific have taken a beating over the past 2 months -- more so than a typical first La Niña winter. The warm pool has continued to expand, and it's likely to strengthen as the MJO moves eastward.

The dynamical computer model consensus also brings Niño 3.4 SSTAs to -0.2°C by MJJ, and 0.1°C by JAS. This is significant because 1) the dynamical models, which are better than the statistical models at catching quick ENSO shifts, still tend to underestimate ENSO trends. Even more interestingly, their underestimation is greater when the forecast rate of change itself is greater. Over the past 8 years, the correlation between the forecast rate of change from Feb to MJJ and the forecast error of the MJJ value itself is a statistically significant 0.87. Admittedly, the sample size is small, but it's a strong enough relationship to warrant consideration, IMO. The latest forecast change from Feb to MJJ is 1.10°C, which puts 2011 on the far right side of this chart -- meaning the dynamical models may be underestimating ENSO warming by anywhere from 0.4 to 1.0°C. Either way, expect positive Niño 3.4 SSTAs by early summer if this correlation holds up.

Since 1950, 10 winter La Niñas were likewise replaced by positive trimonthly SSTAs by fall. 9/10 of them saw the development of an El Niño by the end of the year. And the only other strong ENSO events, warm or cool, that switched to opposing trimonthly SSTAs by MJJ were 1973, 1998, and 2010. I doubt we'll see such a violent (reverse) shift this year, but it's still interesting to note, given the model interpretation above.

FWIW: I'm calculating the trimonthly values using this dataset:

http://www.cpc.ncep.noaa.gov/data/indices/sstoi.indices

SOI has definitely been persistently and strongly positive, but it seems to have little predictive value this early. For instance, it was still very negative in March of 1997 and 2010, and still very positive in March of 1976 -- all years which later observed major ENSO shifts.

It's possible ENSO stays neutral, but I think the evidence overall favors an El Niño at this point.

[gil888]

The MJO is forecast by nearly all the models to progress through phases 6-8 over the next week or so with an amplitude well over 1. If such a progression materializes, the enhanced convection will shift into the western and central Pacific, as illustrated in the ensemble GFS OLR forecast (note the similarity between the forecast and the major WWB in January). This will help further warm the SSTAs.

Moreover, negative subsurface T anomalies under the equatorial Pacific have taken a beating over the past 2 months -- more so than a typical first La Niña winter. The warm pool has continued to expand, and it's likely to strengthen as the MJO moves eastward.

The dynamical computer model consensus also brings Niño 3.4 SSTAs to -0.2°C by MJJ, and 0.1°C by JAS. This is significant because 1) the dynamical models, which are better than the statistical models at catching quick ENSO shifts, still tend to underestimate ENSO trends. Even more interestingly, their underestimation is greater when the forecast rate of change itself is greater. Over the past 8 years, the correlation between the forecast rate of change from Feb to MJJ and the forecast error of the MJJ value itself is a statistically significant 0.87. Admittedly, the sample size is small, but it's a strong enough relationship to warrant consideration, IMO. The latest forecast change from Feb to MJJ is 1.10°C, which puts 2011 on the far right side of this chart -- meaning the dynamical models may be underestimating ENSO warming by anywhere from 0.4 to 1.0°C. Either way, expect positive Niño 3.4 SSTAs by early summer if this correlation holds up.

Since 1950, 10 winter La Niñas were likewise replaced by positive trimonthly SSTAs by fall. 9/10 of them saw the development of an El Niño by the end of the year. And the only other strong ENSO events, warm or cool, that switched to opposing trimonthly SSTAs by MJJ were 1973, 1998, and 2010. I doubt we'll see such a violent (reverse) shift this year, but it's still interesting to note, given the model interpretation above.

FWIW: I'm calculating the trimonthly values using this dataset:

http://www.cpc.ncep....s/sstoi.indices

SOI has definitely been persistently and strongly positive, but it seems to have little predictive value this early. For instance, it was still very negative in March of 1997 and 2010, and still very positive in March of 1976 -- all years which later observed major ENSO shifts.

It's possible ENSO stays neutral, but I think the evidence overall favors an El Niño at this point.

A few points:

1) Remember the RMM diagrams have ENSO removed. If you put it back in, here's what you get:

http://cawcr.gov.au/....Last90days.gif

The RMM-derived figures you showed may show an impressive WWB, but that's going against a La Nina background state. I wonder if the trades will even get to weaker than average for very long-- the January event you mentioned just brought them closer to normal.

2) 8 years is woefully too short to derive meaningful correlations. Yes the models have underestimated things, but is that because the events have mostly been moderate/strong or because it is a true model bias? Also, what is the overall dynamical model skill this time of the year? Not very good for most of them-- but the ECMWF has correctly forecast all Ninos since 1979 (and is going near normal for AS)

3) the GLAAM is not showing the upward movement that I'd like to see to forecast El Nino. Yes it has moved upward recently, but is this in response to the MJO, or is this a longer-term trend starting? October had a huge upward swing, yet very little changed.

http://www.esrl.noaa...-21.seascyc.gif

4) All years that had March Nino 3.4 at -0.8C or below have never gone El Nino since 1950. The sample is shorter than I'd like, but its all we have. 1976 is close to that threshold (-0.7) and it is the one year that I'm watching out for. I wouldn't call it likely, or that there has been any big change, outside of how most La Ninas weaken this time of the year.

5) The March SOI was about 17. The JFM SOI was almost 20. Those are both records for the entire dataset back to 1875. This can't promote El Nino formation in the slightest.

After I say all of that, this is the time of the year that ENSO gives everyone fits, and I don't want to say I am fully sure of no El Nino. It would be very a-climatological, however, and I think it is very unlikely that things are lining up for an El Nino during the summer (I'll eat my words in 2 weeks when a monster WWB forms )

[Supercane]

A few points:

1) Remember the RMM diagrams have ENSO removed. If you put it back in, here's what you get:

http://cawcr.gov.au/....Last90days.gif

The RMM-derived figures you showed may show an impressive WWB, but that's going against a La Nina background state. I wonder if the trades will even get to weaker than average for very long-- the January event you mentioned just brought them closer to normal.

Thanks for the clarification here -- that does put a much different perspective on MJO. Do you know of any archived data on ENSO-included MJO?

2) 8 years is woefully too short to derive meaningful correlations. Yes the models have underestimated things, but is that because the events have mostly been moderate/strong or because it is a true model bias? Also, what is the overall dynamical model skill this time of the year? Not very good for most of them-- but the ECMWF has correctly forecast all Ninos since 1979 (and is going near normal for AS)

I agree that the sample size is very small, but it's still hard to ignore how consistently that has worked 8 consecutive years. They're forecasting a relatively steep ENSO trend, and in the past several years, the steeper the forecast trend = the more they underestimate that trend. We'll see if that works again this year.

3) the GLAAM is not showing the upward movement that I'd like to see to forecast El Nino. Yes it has moved upward recently, but is this in response to the MJO, or is this a longer-term trend starting? October had a huge upward swing, yet very little changed.

http://www.esrl.noaa...-21.seascyc.gif

Not sure how much that matters at this point, since there are some years that had a consistent -GLAAM into Spring and still saw a transition from La Niña to El Niño (1963, 1965, 1968, 2006, etc).

4) All years that had March Nino 3.4 at -0.8C or below have never gone El Nino since 1950. The sample is shorter than I'd like, but its all we have. 1976 is close to that threshold (-0.7) and it is the one year that I'm watching out for. I wouldn't call it likely, or that there has been any big change, outside of how most La Ninas weaken this time of the year.

Yeah, I'm watching out for 1976 as well. Also note that Niño 3.4 in April 1976 was -0.79°C -- it might actually be warmer this April. Not saying that proves an El Niño will form, but it's just as hard, IMO, to use current SSTAs to justify continued cool/neutral ENSO.

5) The March SOI was about 17. The JFM SOI was almost 20. Those are both records for the entire dataset back to 1875. This can't promote El Nino formation in the slightest.

At the moment, no, but how can we be sure the SOI won't rapidly rise in the next month or so?

After I say all of that, this is the time of the year that ENSO gives everyone fits, and I don't want to say I am fully sure of no El Nino. It would be very a-climatological, however, and I think it is very unlikely that things are lining up for an El Nino during the summer (I'll eat my words in 2 weeks when a monster WWB forms )

Haha, well admittedly, the MJO adjustments do make me pause on the El Niño idea. That said, l have a hard time ignoring the model correlation (in spite of the small sample size) and how quickly the subsurface has warmed, especially compared to past La Niña events. So I still think odds of an El Niño are elevated this year, but neutral ENSO obviously cannot be ruled out either. Either way, it'll be interesting to see what happens.

[Floydbuster]

El Nino years make the Eastern Pacific amazing.

In 1997, we of course had Hurricane Linda with 185 mph winds. 2002 brought us the explosive genesis of Hurricane Elida from a TD to a Cat 5 in a 60 hrs time-frame. We also had the landfall of Cat 4 Hurricane Kenna that year. 2006 brought Hurricane Lane to the coast with strengthening 125 mph winds, and 2009 gave us Hurricane Rick, a Linda-clone.

[k***]

strongly agree with the nasonian institute

[rainstorm]

JB says SOI is sky high right now.

[am19psu]

JB says SOI is sky high right now.

I wonder if a monsoon low sitting just offshore of Darwin all week had anything to do with that? Nah, probably not.

[k***]

I wonder if a monsoon low sitting just offshore of Darwin all week had anything to do with that? Nah, probably not.

Why would anyone use the SOI anymore? This isn't the 1920's. We have better indexes.

[am19psu]

Why would anyone use the SOI anymore? This isn't the 1920's. We have better indexes.

Cause JB said so, bro. Get with the program.

[HurricaneJosh]

Nick posted this in the NATL thread, but of course it's relevant here, too:

[aslkahuna]

Well, the main question for starters is will the ATL be as active as forecast? If so, then the inverse relationship between ATL and EPAC would indicate a sub normal season in EPAC. Also to be considered is that when looking at Southern Hemisphere storms, we are still in a Global slowdown which could also affect EPAC. My initial guess is 14 or less total named and 6 hurricanes or less with 2 majors. Should be noted however, is that I blew it last year by going for more than we had.

Steve

[Ed Lizard]

Well, the main question for starters is will the ATL be as active as forecast? If so, then the inverse relationship between ATL and EPAC would indicate a sub normal season in EPAC. Also to be considered is that when looking at Southern Hemisphere storms, we are still in a Global slowdown which could also affect EPAC. My initial guess is 14 or less total named and 6 hurricanes or less with 2 majors. Should be noted however, is that I blew it last year by going for more than we had.

Steve

What is cause and what is effect? Is more African waves becoming ATL TCs a significant factor, or just the fact that what is significant for high EPAC numbers also surpresses NATL numbers and vice versa.

Semi-related question, just found Origins and Mechanisms of Eastern Pacific Tropical Cyclogenesis: A Case Study on Google, what is the breakdown for TCs as far as originating from failed African waves from the Atlantic, the monsoon trough, and interactions between them.

[wxmx]

Well, the main question for starters is will the ATL be as active as forecast? If so, then the inverse relationship between ATL and EPAC would indicate a sub normal season in EPAC. Also to be considered is that when looking at Southern Hemisphere storms, we are still in a Global slowdown which could also affect EPAC. My initial guess is 14 or less total named and 6 hurricanes or less with 2 majors. Should be noted however, is that I blew it last year by going for more than we had.

Steve

Who didn't? The irony is that if we had late forecasts issued for the past season, say in late June, they would have even blew harder, very probably. Who would have said that after a record active June we would have a record inactive JASO. I got the progression of the season good (active to inactive), but I thought it was going to be more gradual.