Which El Niño Index is Best?

Which El Niño Index is Best?

 

A Plethora of El Niño Indices

The November monthly Sea Surface Temperature Anomaly (SSTA) in Niño 3.4 region was a record +2.35, while the 3-month Oceanic Niño Index (ONI) for September-October-November is +2.04, second to a +2.18 for the same period in 1997.  So, is this the strongest El Niño on record or not? How about the monthly SSTA from December 1877 of +2.51?

In reality they are all correct as there is really no “best” metric. One may have elements that best describe a particular season in a particular location, while another may have the best teleconnection for a different time and place. 

A variety of different metrics are used to characterize El Niño; ranging from sea surface temperatures (SST) to sea-level pressure, surface winds, surface temperature and out-going longwave radiation. These are usually expressed in the form of an index; often in terms of the difference from long-term average (i.e., anomalies). Even indices based upon the same metric, like SST, may use different datasets, sampling periods (i.e., weekly, monthly, bi-monthly or tri-monthly) and/or different filtering techniques.

The Niño 3.4 region (map) has arguably the best teleconnections to seasonal weather in the United States and is widely used as a sampling area for SSTAs.

The Oceanic Niño Index (ONI), is the mostly widely used index in the United States to characterize El Niño events.  The ONI is the 3-month SST Anomaly (SSTA) for Niño 3.4 and calculated from moving 30-year average values. See http://ggweather.com/enso/oni.htm and http://www.cpc.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml.

The Niño 3.4 region SST is also sampled on both a monthly (http://www.cpc.ncep.noaa.gov/data/indices/ersst4.nino.mth.81-10.ascii) and weekly (http://www.cpc.ncep.noaa.gov/data/indices/wksst8110.for) using the ERSST4 dataset back to 1950. There is also monthly Niño 3.4 data going all the way back to 1870 using the HadISST1 dataset  (http://icdc.zmaw.de/1/daten/ocean/hadisst1.html).

The Southern Oscillation, which was identified by British mathematician Sir Gilbert Walker in the early 1900s, is a periodic "see-saw" of pressure patterns in the tropical Pacific. This pattern was later linked to occurrences of El Niño and is the SO part of the combined acronym ENSO for El Niño Southern Oscillation. It is usually expressesed as the standardized Southern Oscillation Index (SOI). See https://www.ncdc.noaa.gov/teleconnections/enso/indicators/soi/.

The El Niño Modoki (translated from Japanese for "similar but different") Index quantifies ENSO events that are warmer in the central Pacific than the typical El Niño warming in the eastern Pacific. See http://www.jamstec.go.jp/frcgc/research/d1/iod/enmodoki_home_s.html.en.

And the Multivariate ENSO Index (MEI) brings together six different elements (sea-level pressure, zonal and meridional surface wind, sea surface temperature, surface air temperature and total cloudiness). See http://www.esrl.noaa.gov/psd/enso/mei/.

An excellent technical analysis of these various indices by Anthony Barnston of IRI can be found at https://www.climate.gov/news-features/blogs/enso/why-are-there-so-many-enso-indexes-instead-just-one.

Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com

 

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All-Time Record Niño Region 3.4 Anomaly

All-Time Record Niño Region 3.4 Anomaly

 

The just updated Niño 3.4 region SST anomaly for November 2015 is +2.35.  This is the highest monthly SST anomaly (for any month) going back to the beginning of the dataset in 1950.  Previous the high was +2.33 in November 1997.



Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com

 

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Weather Geeks Interview re El Niño Misconceptions

Weather Geeks Interview re El Niño Misconceptions

 

Last month I did an interview with Dr. J. Marshall Shepard on The Weather Channel's "Weather Geeks" show about El Niño Misconceptions. It has been posted online here: https://www.youtube.com/watch?v=15REf4BqRQo&feature=youtu.be

The source of much of the information in that interview can be found at http://ggweather.com/enso/enso_myths.htm .

Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com

 

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Monthly El Niño Analysis: Beware December!

Monthly El Niño Analysis: Beware December!

 

To date, much of the retrospective analysis of California rainfall during El Niño rainfall seasons has been looking at the teleconnections between seasonal totals and the strength of the El Niño events.  This analysis focused on monthly rainfall anomalies across California; and in doing so the biggest takeaway was that December during both strong and very strong events was historically drier than normal across most of the state north of the Tehachapis.



For a complete month-by-month and station analyses go to http://ggweather.com/enso/monthly/ .

Other El Niño resources can be found at http://ggweather.com/enso.htm .

Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com

 

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Would the amount of rain in the Carolina’s this past week be enough to end the California Drought? Not even close!

Would the amount of rain in the Carolina’s this past week be enough to end the California Drought? Not even close!

 

Several recent news reports have stated that the rain that fell over North and South Carolina this past week would be enough to erase the California drought. this was based on comparing an estimated 11 trillion gallons that the Carolinas received this past week to an amount from a NASA study that also used an 11 trillion gallon figure needed for California.  However the numbers don’t add up.

It’s been estimated that the average rainfall that fell across the Carolinas was 10.4 inches.  With a total area for North and South Carolina of about 85,000 square miles that actually equates to about 15.5 trillion gallons.  [Specifically 1” of water over 1 sq. mile= 17,378,560 gallons; times 10.4” of rain, times 85,839 sq. miles equals 15,514,285,403,136 gallons]

Now, looking at California. The statewide average rainfall for California is about 24 inches, and in round numbers the 4-year rainfall deficit is approximately a year’s worth of rainfall. Given the total California area of over 163,000 square miles that’s a phenomenal 68 trillion gallon deficit, or over four times the rain that fell on the Carolinas!  [Specifically 1” over 1 sq. mile= 17,378,560 gallons, times 24” of rain, times 163,694 sq. miles equals 68,274,384,015,360 gallons]

Some of the confusion arises from last December's NASA study that had a headline of "Needed: 11 Trillions Gallons to Replenish California Drought".  However, reading the entire article reveals the 11 trillion gallon amount was for only the Sacramento and San Joaquin river basins. And finally, it should be noted that to "end the drought" in some areas of California it may take more than a year's worth and in other areas less.

Update (10/9): Please note the rainfall amounts for California (above) are only to make up the deficit. To "end the drought" we would need to make up most of teh deficit, PLUS the normal rainfall of the winter of 2015-16, or another 24 inches.  Bottom line, we would be looking at as much 8 times the rains that flooded the Carolinas.


Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com 






 

 

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El Niño Circulation Reanalysis; September Summary; Worldwide AQI

El Niño Circulation Reanalysis; September Summary; Worldwide AQI

 

Here's a reanalysis of the 500 mb heights, height anomalies and the precipitable water anomalies for the strong and very strong El Niño winters (Nov-Mar). See http://ggweather.com/enso/reanalysis/ These really brought back my recollections from 1997-98 of the nearly continuous zonal flow across the Pacific, and the models being consistently too slow with the embedded short-waves.

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Not surprisingly, September was warmer than normal statewide while precipitation ranged from negligible to epic (Los Angeles, 996% of normal). But the Southern California rainfall must be kept in perspective as normal in LA for September is on 0.24". See  http://ggweather.com/calif/sep2015.htm 

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Interesting website with near-real-time Air Quality Index (AQI) values color-coded world-wide.  http://aqicn.org/here/ 


Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com 

 

 

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Recent El Niño Background Articles/Papers

Current El Niño Background Resources

 

A number of excellent and timely articles/papers about El Niño have been posted in the past few weeks, and I have collected some of them below. There is lots of other great stuff out there so please drop me a note if there is something I have missed.

IRI - September Climate Briefing: More Confidence than Ever


NOAA - United States El Niño Impacts


NCAR - Watch 2015 and 1997 El Niños Build, Side-by-Side


NOAA Climate Office - What can drought-stricken California expect from the El Niño winter forecast?,

NOAA Climate Office - California Drought Assessment

Commentaries about the"blob"
Cliff Mass (UWash) - Godzilla El Nino Versus The BLOB: Who Will Win?

Weather West -  Record-strength El Niño likely to bring wet winter to California in midst of worst drought on record 


Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com






 

 

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Butte and Valley Fire Weather Links

Fire Weather Links

 

In response to numerous requests for weather information in regards to the Valley and Butte Fires, here are some fire weather resources:

Fire Weather Forecasts:  NWS Sacramento Fire Wx Forecasts  (Valley Fire CAZ507, Butte Fire CAZ267 & CAZ220)

Current observations:  http://www.wrh.noaa.gov/map/?obs=true&wfo=sto 

Other Fire Weather Links:  http://ggweather.com/firewx.htm 

Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com






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Warm August Caps Warm Summer Over Most of California - Lots of SF Records

Warm August Caps Warm Summer Over Most of California - Lots of SF Records

 

Most major cities across California had warmer than normal maximum and minimum temperatures both for August and for entire summer (i.e., June, July, August). 

August saw average monthly maxima ranging from rigth at normal  at Fresno to 3.7 above normal at San Franciso and 4.2 above normal at San Diego. Only San Jose was cooler than normal with a  -0.2 degree anomaly.  The average monthly minima had even warmer anomalies.  San Francisco's average monthly minimum was 5.1 degrees above normal, with the 60.2 degrees smashing the previous record of 58.2 set just last year. Elsewhere average monthly minima were  1.4 (Fresno) to 3.7 (Los Angeles) degrees above normal.  See http://ggweather.com/calif/aug2015.htm 

Summer (JJA) was also almost universally warmer than normal, again with San Jose being the outlier. Redding was the warmest with a summertime maximum anomaly of 4.2 degrees above normal, followed by San Diego at 3.0 above normal.   Redding and San Francisco had the warmest June-July-August average minimum anomalies with +4.8 and +3.7 degrees respectively.  http://ggweather.com/calif/summer2015.htm 

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San Francisco's warm August saw 16 new daily records.  A new record max of 90 degrees was set on August 16th. But it was the 15 new or tied record high minimums that were pretty eye-catching. See the just updated SF Daily Almanac at http://ggweather.com/sf/almanac.html#August  for details.

Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com




 

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