I have an El Nino question

[Taffy]

I have been reading the posts about the results of an El Nino. I have become confused on the results stemming from a weak El Nino and a Moderate/Strong El Nino. I seemed to come away with the impression that a weak El Nino meant a much more severe and wet winter than a moderate or severe El Nino. I can't understand how that could be and I would love the results explained for each strength of an El Nino.

Thanks.

[wjs3]

Taffy:

I wrote this for a class I was in. It's not perfect, and its focus is the 82-83 el nino, but it should give you a better idea of what an el nino is and does.

http://www.personal.psu.edu/users/w/j/w ... _intro.htm

CIRES also has a page with a lot of links to great resources on El Nino for your reading pleasure here:

http://www.cdc.noaa.gov/ENSO/

[wxmann_91]

I have been reading the posts about the results of an El Nino. I have become confused on the results stemming from a weak El Nino and a Moderate/Strong El Nino. I seemed to come away with the impression that a weak El Nino meant a much more severe and wet winter than a moderate or severe El Nino. I can't understand how that could be and I would love the results explained for each strength of an El Nino.

Thanks.

El Nino has far ranging effects from tropical cyclone activity in the Atlantic and Pacific to droughts in Australia to floods in the southern CONUS. Without going into too much detail, El Nino winters can be severe in the northeast, only that in a strong Nino, the pattern would be progressive enough so that any snowstorm in the northeast wouldn't be blocked. Same cannot be said for a weaker Nino when the strong subtropical jet associated with all Ninos can phase with the polar jet and create monsters - President's Day Snowstorm II in 2003 was a good example.

Tornadoes, since a strong Nino keeps things progressive due to its jet, and prevents huge intrusions of cold air in the east, a strong Nino can bring hoards of outbreaks in the southern U.S. (1998 was a good example). But the cold east during weak/mdt ninos don't support this.

Hurricanes, subtropical jet = shear over Atlantic. Inverse relationship between Atlantic and EPAC, so EPAC heats up. In addition warmer waters in Pacific promote stronger convection and thus more TC's, from the eastern WPAC to the EPAC. Effects in the tropical cyclone can vary and the difference here between weak and strong Nino is pretty insignificant.

[Taffy]

Okay, I loved the assignment. Very visual, which is excellent for me.

I am very curious to see what this winter will be like in southern Florida. I can remember very cold winters here. I am going to have to get the dates of the last El Nino's and consider the weather then.

It "snowed" one morning either late in 98 or early 99. I wonder if that was an El Nino.

Thank you so much

[wjs3]

glad you liked it. It was a lot of fun (though an insane amount of time) to do.

I grew up in south florida (live in Chicago now) and remember snow there in 1977.

Take a look at this....Red is El nino...Blue is La Nina.

http://www.cpc.ncep.noaa.gov/products/a ... ears.shtml

[Taffy]

That was interesting. The numbers represent the temperate deviation from the average???? If so, then it doesn't seem like enough to make a difference.

I noticed alot of short cycling. How can the weather center be so sure that this will last through the summer of 07?

[wjs3]

Yes, they are a set of temperature anomalies in certain areas of the equatorial pacific. there is some more detail on the kinds of metrics used to measure and predict ENSO in the weekly expert assessment put out by the CPC:

http://www.cpc.ncep.noaa.gov/products/a ... ts-web.ppt

(by the way, the CPCs ENSO page is great too: http://www.cpc.ncep.noaa.gov/products/p ... enso.shtml)

The short answer to your question is that other than informed estimates (informed by long range, climate models), things like this are very, very hard to forecast. For instance, going into this hurricane season, the "call" was for a moderate La nina. It's been more neutral than anything, and even starting to tip toward El nino. Climate forecasters do the best they can, but it, like all forecasting, can be very, very tough.

Best!

[wxmann_91]

Okay, I loved the assignment. Very visual, which is excellent for me.

I am very curious to see what this winter will be like in southern Florida. I can remember very cold winters here. I am going to have to get the dates of the last El Nino's and consider the weather then.

It "snowed" one morning either late in 98 or early 99. I wonder if that was an El Nino.

Thank you so much

The winter 98-99 was characterized by a strong Nina.