Extreme La Nina -Multivariate ENSO Index (MEI) Sets Records

ixus

Would appreciate your thoughts on this.

Extreme La Nina

The most recent (July-August) MEI value shows a continued drop from earlier this year, reaching -1.81, or 0.64 sigma below last month's value, and 2.35 standard deviations below April-May, both record-fast drops for this time of year. In fact, the three-month drop set a new all-time record for any time of year, beating a 2.33 sigma drop in 1998.



The most recent MEI rank (2nd lowest) is clearly below the 10%-tile threshold for strong La Niña MEI rankings for this season. One has to go back to 1955 to find stronger La Niña conditions for this time of year in the MEI record, and back to September-October 1975 for lower MEI values at any time of year.


Conclusion: We have one heck of big La Nina that has formed very quickly. We have not seen conditions like this in 55 years. What might it mean for the US:

-Above-average precipitation in the Pacific Northwest.

-Below-average precipitation in the Southwest and in portions of the middle and lower Mississippi Valley and Tennessee Valley.

-Increased Atlantic hurricane activity by decreasing the vertical wind shear over the Caribbean Sea.

Su Campu

Yes, Joe Bastardi was talking about that a week or two ago

Redsunset

redsunset wrote: »

"One has to go back to 1955 to find stronger La Niña conditions for this time of year in the MEI record, and back to September-October 1975 for lower MEI values at any time of year."


















In the context of recent plunge of the MEI into strong La Niña conditions, this section features a comparison figure with strong La Niña events that all reached at least minus one standard deviations by June-July, and a peak of at least -1.4 sigma over the course of an event. The most recent bigger La Niña events of 1998-2001 and 2007-09 did not qualify, since they either did not reach the required peak anomaly (the first one) or became strong too late in the calendar year (both).

The most recent (July-August) MEI value shows a continued drop from earlier this year, reaching -1.81, or 0.64 sigma below last month's value, and 2.35 standard deviations below April-May, both record-fast drops for this time of year. In fact, the three-month drop set a new all-time record for any time of year, beating a 2.33 sigma drop in 1998. The most recent MEI rank (2nd lowest) is clearly below the 10%-tile threshold for strong La Niña MEI rankings for this season. One has to go back to 1955 to find stronger La Niña conditions for this time of year in the MEI record, and back to September-October 1975 for lower MEI values at any time of year.

Negative SST anomalies have overspread much of the eastern (sub-)tropical Pacific in the latest weekly SST map.




Many of these anomalies are now in excess of -2C. For an alternate interpretation of the current situation, read the latest NOAA ENSO Advisory which represents the official and most recent Climate Prediction Center opinion on this subject. In its latest update (5 August 2010),
La Niña conditions are expected to strengthen and last through the upcoming Northern Hemisphere winter.







So there's a bit of info for you Deep,if you have not already come across it.

Interesing now to see how this plays out with global winter temps.

Yes we've all been keeping a close eye on this,have been sticking info into winter outlook thread but thanks it deserves its own thread

maquiladora

Whats the historical relationship between an extreme La Nina and weather conditions for Ireland/W Europe?

weisses

maquiladora wrote: »

Whats the historical relationship between an extreme La Nina and weather conditions for Ireland/W Europe?

Yeah ?? Does anyone have some dusty old charts from 1955 ??

Deep Easterly

maquiladora wrote: »

Whats the historical relationship between an extreme La Nina and weather conditions for Ireland/W Europe?

I wonder is there any? or are the long-term effects more prominant than the short term ones?

A prolonged La Nina kicked off in the spring of 1954, which was to last until early 1957. During this period, and going only by British records, there seemed to be an increase in cold snaps during the winter months which were followed by cold springs. This is nothing more than basic generalisation though, as equally, there were notable mild spells also within these seasons during this period.

http://www.personal.dundee.ac.uk/~taharley/1955_weather.htm


I wonder though, did this actual La Nina have a longer term effect? in that it had an influence on the notably cool period of the early 1960's? Or was this cooler period directly influence by the lack of any El Nino events during this time? Or a combination of both????? :D

Hard to say, but it is interesting to note that a 3 year long La Nina occured in the mid 1970's, which in turn seemed to be followed by a series of cooler winters which extend right into the early 80's.


Edit: actually, looking back at what I have just spewed out, it just seems to be a long round-a-bout way of saying that I haven't got a clue!!

Redsunset

Operation 'Snowdrop'
The cold winter of 1955
by Philip Eden

And as Deep as pointed out,

'Operation Snowdrop' was the name given to the military operation to deliver food and medical supplies to snowbound districts in Scotland over fifty years ago.

The RAF operated fixed-wing aircraft out of Kinloss primarily to drop animal fodder, and the Royal Navy flew helicopters from Wick to carry supplies to villages and farms cut off by drifts over 30 feet high. The services flew nearly 300 sorties in all to provide relief to communities in Shetland, Orkney, Caithness, Sutherland, Ross and Cromarty, and Inverness-shire.

The winter of 1955 was the coldest and snowiest between the two Big Freezes of 1947 and 1963, but in many parts of the Scotland it was reckoned to be the worst of the lot.

Severe weather lasted from January 4th-22nd, and returned from February 8th until March 11th. The snow in northern Scotland arrived on a gale force northerly wind, and even when the snow stopped falling the wind continued to blow it into deep drifts thwarting all attempts to clear roads, most of which remained impassable until well into March.

Level snow lay 60cm deep by February 23 over the northern half of Scotland, and was measured at 90cm deep at Drummuir Castle, southeast of Elgin. The wintry weather extended to England and Wales for long periods too, especially during the second half of February with a dramatic snowstorm in Cornwall during the closing days of the month.

Redsunset

http://www.seaclimate.com/4/pdf/4_21.pdf

1946/47 is regarded as El Niño period, 1928/29 is listed as an anti-El Niño event (La

Niña).

February 1929 was at many Middle European stations the coldest ever
measured. The deviations were up to minus 8-12°C. In Greenland, however,
it was the mildest since observation started4. According to Rodewald5 the

tropical Atlantic was the source of that extreme winter.

Redsunset

littlema

Okay Weatheries, is this why Oz is having such devastating floods on the Eastern seaboard for such a length of time? This must be one powerful La Nina and we have had our coldest winter too!!
Roll on El Nino or at least a few normal years to make up for all this calamity. Ma

Su Campu

little ma wrote: »

Okay Weatheries, is this why Oz is having such devastating floods on the Eastern seaboard for such a length of time? This must be one powerful La Nina and we have had our coldest winter too!!
Roll on El Nino or at least a few normal years to make up for all this calamity. Ma

It is the cause of the wet Australia and dry New Zealand.

http://www.bom.gov.au/climate/enso/

nilhg

It's influence stretches further than the Pacific, if you're wondering why your bread gets dearer next year read on

http://www.heraldsun.com.au/news/breaking-news/la-nina-in-death-throes-forecasters/story-e6frf7jx-1226055358698

"The La Nina weather event that brought unprecedented rain and flooding to much of Australia has now weakened, with most indicators now showing neutral conditions have returned to the Pacific Ocean," The Weather Channel meteorologist Tom Saunders said.