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EPAC Tropical Action 2011


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EPac hurricane season 2011 forecast.

Last year things were quite extreme in the basin. From record high early season activity to record dullness, as June 2010 died, so did the EPac TC activity.

The following quote sums my thinking last year before the season started, from my last year's forecast:

The change will be gradual as we transition out of a Niño state, so my thinking is that we get an average to probably slightly above average first half of the season, with a significant decrease as the season progresses, and we probably finish with a below average season for September and October.

Scratch the "gradual", the "average to probably slightly above average first half of the season" and replace the "below average season for September and October" with "way below average season for JASO", and my forecast should have been a lot better... but truth is, it was a bust wrt numbers.

2010 forecast 15/6/2

2011 verfication 7/3/2

2011 marked two records of inactivity related to these numbers, breaking 1977's 8 named storms and that same year's 4 hurricanes. The MH low activity record is still in 1977's posession with 0.

2011

Time to stop licking my wounds, and look forward for what this year might bring. First, the shocker news. This year activity has a lot higher chance of being more active than last year :o ... still recovering from the impact? Let's break down some of the major factors that rule the rooster in the forgotten basin.

ENSO

We see conflicting signals. First, the La Niña that bloomed last year, peaking early this past winter is declining markedly, the latest ONI trimonthly indicates weak Niña conditions, but current SSTAs in ENSO 3.4 indicate neutral cold...and still warming.

Trade winds near the dateline have been relentless, with easterly anomalies almost entirely since last summer. SOI has been record high for many months in a row, second only to 1917-1918, with records going back to 1876. The same with +OLR and -AAM, which both have been pretty much Niña like for many months now.

OTOH, the OHC in the ENSO regions have been steadily increasing, totally erasing any cold subsurface pools we had in the past, especially in the eastern portion of the ENSO regions, where a warm bubble has developed. ENSO regions 3.4 and 4 are barely holding cooler than normal in the surface and the shallow subsurface.

Currently, there are indications of a less Niña atmosphere, with a high amplitude MJO crossing the Pacific, which is not common on Niña years, plus a spike in the AAM into positive territory. These signals foretell a slack in the easterlies, and a more favorable environment for WWBs/KW to propagate east. But there's still no indication of either, with a probable return of slightly stronger than normal easterlies near the dateline. This might be short term, but shows a definite change in the pattern if it holds trough the next month or two.

My call is for a neutral ENSO on average for JASO, with ongoing warming in positive SSTAs in ENSO 3.4 region in the first half and some dipping in the second half to slighly colder.

The ENSO will probably be a neutral factor this season.

PDO

It's still very distinctively negative at the moment, and I expect little change during hurricane season, maybe some temporary weakening in tandem with the ENSO, but not by much. We are still currently in the negative long term state, and usually this hinders cyclogenesis/strengthening, especially away from the Mexican coast. Long trackers or basin jumpers will be scarce to non existent, also the naked swirl post tropical low might be a common sight.

PDO is a negative factor.

SSTAs

SSTAs from the eastern part of the Pacific Equatorial countercurrent are highly correlated with the ENSO state, usually being warmer than normal during El Niño events and colder during La Niñas, but this year the SSTAs near the Mexican Pacific coast are warmer than normal, meaning that if atmospheric conditions are favorable, we might see good conditions for near the coast cyclone genesis/strengthening. Other than near the coast of Mexico, things look not so good, but since most of the action usually starts near the continent, this might be a slightly favorable factor.

Overall there might be a slightly negative environment for EPac activity, plus, with the expected above average activity in the Atlantic, a slightly toned down hurricane season for the basin is expected, with a slightly lower chance for landfalls.

  	Verification 	SMN        wxmx
2007  	11/4/1      	14/7/1   13/7/2
2008  	15/7/2      	15/8/3   14/8/2
2009  	17/7/4      	13/7/3   17/10/4
2010   	7/3/2     	15/5/1   15/6/2
2011   	? 		14/8/3   14/7/2

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GFS is popping something near 120E this weekend, which agrees with statistical OLR forecasts. Would be weak and short-lived if it happens.

This is going to be a tease. I doubt it will become much more than a few thunderstorms.

The Gulf of Tehuantepec (or the Western Caribbean) will be the area to watch around the 20th, though, I think.

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I'm going to stay with my 14/6/2 that I posted early in this thread. In the meantime, the ENSO headed into neutral territory has me scratching my itchy scalp about what to do about the monsoon. The relationship between the monsoon and EPAC TC activity is not that definitive. Our moisture is dual sourced, but the most important monsoon disturbances in the North American Monsoon (at least the northern segment) are mid level disturbances of subtropical origin originating in the GOM.

Steve

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Thanks, Jorge, for the forecast. It makes sense, and I'm encouraged by the warm SSTs (and your hunch Re: good conditions) near the coast, as of course that's the only part of the basin that matters. (Really, who cares about all them fish halfway between HI and MX? :D)

Re: 2010, don't be too hard on yourself. It looks like everyone got burned on the numbers-- and you nailed the overall seasonal pattern.

Cool that you and Steve (aslkahuna) are calling for pretty-much the same numbers. I'd say you two are AmericanWx's two experts on this basin. (Well, me, too-- but from the historical perspective only. :sun:)

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Hopefully we get something soon. :popcorn: Most seasons wait until about the second week to develop its first cyclone around 21-30th of May. Some not until clear into June.

Yeah, it would be nice to see a little early-season action. But I've resolved to be patient. As I often say in EPAC discussions, the real fireworks in this basin usually happen in October.

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Wow quite a blowup! Wasn't the GFS showing some action to begin flaring up just around this time a week or so back?

As mentioned above, the GFS doesn't really do much with the system, despite analyzing the mass of convection reasonably well on the 06z run. The shear is relatively low, however, if the system can stay around 10-12N. So its not unreasonable that we could expect further organization in the next 24 hours.

dbtzjs.gif

In any event, it likely won't be long till we see our first Invest designation!

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