Current ENSO Status, Probabilistic Forecast for the Lower Missouri River Valley,

Current ENSO Status,Probabilistic Forecast for the Lower Missouri River Valley,

and much, much more…

WFO Pleasant HillWinter Weather Seminar

08 November 2010

Niño Indices: Recent Evolution

The latest weekly SST anomalies are right around -1.4oC (all the way from the Nino 4

region to the Nino 1+2 region)

Sub-Surface Temperature Departures (oC) in the Equatorial Pacific

• Since the late spring, negative surface and sub-surface temperature anomalies have been present across the equatorial Pacific•The most recent period (below) shows persistent strong negative anomalies (a very large reservoir greater than 4oC below average) in the central and eastern Pacific near the 100m depth.

Upper Oceanic Heat Content Evolution in the Equatorial Pacific

•Oceanic Kelvin waves have alternating warm and cold phases. The warm phase is indicated by dashed lines. Down-welling and warming occur in the leading portion of a Kelvin wave, and up-welling and cooling occur in the trailing portion.

• Last winter and early spring, several oceanic Kelvin waves created strong downwelling and maintenance of El Nino conditions• Since May 2010, these Kelvin wave episode ceased and allowed for upwelling of cooler subsurface water• Recently, the downwelling (warming) phase of a weak Kelvin wave was evident in the central Pacific

Low-level (850-hPa) Zonal (east-west) Wind Anomalies (m s-1)

Stronger than average easterly trade winds since May

Most recent 850 mb Zonal wind anomalies

SST Outlook: NCEP CFS Forecast Issued 17 October 2010

The CFS ensemble mean (heavy blue line) predicts La Nina will last through at least the Northern Hemisphere spring 2010-11.

Multi-Variate ENSO Index (MEI)

• MEI is calculated using 6 measured variables over the tropical Pacific: sea level pressure (P), surface u-wind component (U), surface v-wind component (V), sea surface temperature (S), surface air temperature (A), and fractional sky cover (C)•These variables are normalized seasonally to a 1950-93 reference period, with MEI calculated by the co-variance matrix of the combined fields as the first order unrotated principle component. MEI is calculated on 12 bi-monthly seasons, with negative values representing the cold ENSO phase, and positive values the warm phase

Multi-Variate ENSO Index (MEI)

Standardized MEI value of -2.0 is one of the lowest ever recorded

Composite La Nina DJF Heightand Temperature fields

• Height and Temperature anomalies calculated for all moderate to strong La Nina winter seasons as compared to a 1968-1996 climatology

• As is typical during La Nina episodes, more intense north Pacific jet energy, with more frequent northwestern CONUS troughing and southeastern CONUS ridging

Composite La Nina DJF Heightand Temperature fields

• Height and Temperature anomalies calculated for only the best matching La Nina winter seasons (1998-99, 1988-89, 1973-74, 1970-71)

• Composites for the best matching La Nina winter are consistent with those for all moderate to strong La Nina winters. Possibly more tendency for blocked flow at high latitudes

Typical Weather PatternsDuring La Nina Winters

La Nina Temperature and Precipitation (OND) Anomalies and Frequencies

• Anomalies are calculated for all La Nina years, with frequencies determined by the number of years which the certain anomaly occurred

• Late Autumn and early winter La Nina years are characterized by warmer and drier than average conditions from the southern plains through western Great Lakes. Frequency counts indicate fairly good historical probabilities of this outcome.

La Nina Temperature and Precipitation (DJF) Anomalies and Frequencies

• By mid-winter during La Nina years, both anomalies and frequencies in temperature and precipitation become split over the United States, with little predictable influence over the central Plains and Lower Missouri River valley.

• Remember, these anomalies and frequencies are calculated for all La Nina years. There are some differences between weaker events and stronger events.

U. S. Seasonal OutlooksDecember 2010 – February 2011Temperature Precipitation

Outlooks combine long-term trends and soil-moisture effects, with typical ENSO cycle impacts, when appropriate.

Local 3 Month Temperature Outlook Dec 2010-Feb 2011

Local Kansas City Temperatures Outlook based on historical comparison of local temperatures with Climate Division

temperature probabilities. Initialized from CPC DJF temperature outlook.

Winter Temperature and Precipitation La Nina Analogs

Temperature 42.7 31.3 26.9 33.0 43.8 35.5 30.4Year Nov Dec Jan Feb Mar 5-Mo Avg DJF Winter Avg

Best Strong 1973-74 45.5 30.0 23.8 35.3 46.9 36.3 29.7Best Strong 1988-89 44.8 35.2 37.7 22.8 43.8 36.9 31.9

Best Moderate 1998-99 48.0 34.7 27.7 41.2 42.5 38.8 34.5Best Moderate 1970-71 44.4 38.9 27.6 31.5 43.6 37.2 32.7

Strong 1949-50 49.8 37.1 30.3 35.4 40.0 38.5 34.3Strong 1955-56 40.0 31.8 27.9 34.4 45.2 35.9 31.4Strong 1975-76 45.9 34.0 27.5 42.7 44.9 39.0 34.7Strong 1999-2000 51.9 35.8 31.7 40.8 47.1 41.4 36.1

Moderate 1954-55 48.9 36.9 32.4 31.4 43.7 38.7 33.6Moderate 1964-65 49.8 32.3 31.4 32.3 33.9 35.9 32.0Moderate 2007-08 43.9 29.9 27.5 27.7 41.6 34.1 28.4

La Nina Composite All Years 46.6 34.2 29.6 34.1 43.0 37.5 32.7

Precipitation 2.30 1.64 1.15 1.31 2.44 8.84 4.10Year Nov Dec Jan Feb Mar 5-Mo Total DJF Winter Total






Winter Snowfall Accumulation And Frequency La Nina Analogs

Snowfall 1.3 4.3 5.8 5.0 2.6 19.0 15.1Year Nov Dec Jan Feb Mar 5-Mo Total Winter Total






# Days > T (> 2.0) 1 (0) 4 (1) 5 (1) 4 (1) 2 (0) 16 (3) 13 (3)Year Nov Dec Jan Feb Mar 5-Mo Total Winter Total

Best Strong 1973-74 0 7 (1) 5 (1) 1 1 14 (2) 13 (2)Best Strong 1988-89 1 1 1 10 (1) 0 13 (1) 12 (1)

Best Moderate 1998-99 0 3 5 (1) 4 2 14 (1) 12 (1)Best Moderate 1970-71 0 2 (1) 3 4 (2) 3 (2) 12 (5) 9 (3)

Strong 1949-50 0 3 (1) 3 2 1 9 (1) 8 (1)Strong 1955-56 3 2 (1) 6 (2) 6 (2) 4 (1) 21 (6) 14 (5)Strong 1975-76 2 (2) 3 6 (1) 4 (1) 1 16 (4) 13 (2)Strong 1999-2000 0 4 4 1 (1) 1 10 (1) 9 (1)

Moderate 1954-55 0 0 5 (1) 6 (1) 3 (1) 14 (3) 11 (2)Moderate 1964-65 2 3 (1) 4 4 (1) 9 (1) 22 (3) 11 (2)Moderate 2007-08 2 6 (2) 6 (1) 4 (1) 1 19 (5) 16 (5)

La Nina Composite All Years 1 3 4 4 2 15 (3) 12 (2)

Southern Oscillation Index (SOI) as a Proxy for Historical ENSO State

• SOI Index of +25 highest measured since November 1973 and highest September value since 1917

• SOI Index is a normalized value of the monthly SLP difference between Tahiti and Darwin versus the long term mean.•Positive values = enhanced trade winds and La Nina state•Negative values = weaker trade winds and El Nino state

Historical Southern Oscillation Index (SOI) Analog Years for Moderate to

Strong La Nina Episodes Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec1889 -25.9 -1.7 -27.5 -0.5 -1.9 22.0 1.6 2.1 11.1 4.2 23.0 22.0

1890 20.8 11.0 14.3 6.9 3.6 5.8 -2.3 -3.1 9.3 3.6 2.6 0.6

1906 -3.5 -7.4 -5.2 -8.8 1.3 -3.9 6.8 15.5 18.3 9.1 21.7 4.7

1907 5.1 1.6 -0.3 4.5 10.0 8.3 -4.3 -8.2 0.2 0.6 -2.0 8.8

1910 5.6 15.2 12.7 5.3 0.5 22.0 20.5 9.8 15.3 10.3 19.7 15.9

1911 3.2 1.6 3.5 2.0 -8.2 -12.0 -12.8 -12.1 -8.8 -11.7 -7.3 -1.4

1917 5.1 10.0 18.1 21.8 21.8 21.2 28.3 34.8 29.7 15.2 21.0 22.5

1918 14.6 16.6 -2.0 16.8 10.0 -4.7 -14.1 -4.4 -8.2 -5.0 1.3 -8.0

1938 7.5 3.4 -3.6 3.6 13.1 18.0 18.5 13.0 7.5 12.8 1.9 13.8

1939 17.0 7.7 11.6 9.4 -1.1 -1.5 8.1 -0.5 -9.4 -14.7 -8.0 -8.6

• SOI Index persistence greater than ±8.0 indicative of sustained enhanced or weaker trade winds, and well developed ENSO phase

• Can be used as a proxy for La Nina analog years prior to 1949

• Although SOI Index does not always fall in line with ENSO state based entirely on SST anomalies, the larger SOI values generally do correspond with accepted ENSO state

Winter Temperature, Precipitation, and Snowfall La Nina Analogs Prior to 1949

Temperature 42.7 31.3 26.9 33.0 43.8 35.5 30.4Year Nov Dec Jan Feb Mar 5-Mo Avg DJF Winter Avg

1938-39 45.1 36.1 38.5 29.4 45.9 39.0 34.71917-18 47.7 23.4 17.3 33.9 50.8 34.6 24.91910-11 43.8 31.9 32.8 36.0 46.8 38.3 33.61906-07 41.8 35.7 31.1 33.4 52.1 38.8 33.41889-90 40.0 46.8 29.8 34.0 38.3 37.8 36.9

La Nina Composite 43.7 34.8 29.9 33.3 46.8 37.7 32.7

Precipitation 2.30 1.64 1.15 1.31 2.44 8.84 4.10Year Nov Dec Jan Feb Mar 5-Mo Total DJF Winter Total

1938-39 2.70 0.55 1.28 0.98 1.14 6.65 2.811917-18 0.06 0.45 0.94 1.53 0.48 3.46 2.921910-11 0.28 1.25 0.61 6.76 1.06 9.96 8.621906-07 3.08 1.62 4.54 0.91 2.50 12.65 7.071889-90 2.38 0.14 1.49 0.53 1.15 5.69 2.16


Snowfall 1.3 4.3 5.8 5.0 2.6 19.0 15.1Year Nov Dec Jan Feb Mar 5-Mo Total DJF Winter Total

1938-39 2.0 0.0 6.1 5.8 0.3 14.2 11.91917-18 0.1 5.3 10.3 0.1 0.0 15.8 15.71910-11 0.2 1.3 0.1 12.3 0.2 14.1 13.71906-07 6.0 0.1 2.5 7.1 0.0 15.7 9.71889-90 0.0 M 7.3 4.0 2.0 M M


Summary

• The atmospheric circulation and precipitation patterns, as well as SST anomalies indicate moderate to strong La Nina conditions already present across the entire tropical Pacific Ocean• SST anomalies are around-1.4oC in the 4 Niño regions, indicative of the beginning of a strong La Nina episode• Based on recent trends and a majority of the statistical and dynamic coupled model forecasts, La Nina conditions should maintain their intensity during the next several months and will likely continue into at least the spring months of 2011 – possibly challenging some of the stronger La Nina episodes on record.

Summary

• Based on past 10 year temperature trends and composites of past moderate to strong La Nina winter seasons, there exists a slightly better than normal chance that winter temperatures in eastern Kansas and Missouri will be above average• Choosing a best analog set of the top 4 matching winter seasons based on SST anomalies and MEI time series, the highest probabilities point towards warmer than average temperatures early in the winter season, with less predictability and larger variability later in the winter • There is no reliable predictability concerning precipitation or snowfall based on La Nina composites or analogs with a wide range of historical outcomes

And now for SomethingCompletely Different…

• MJO Phase must be in a progressive state lasting 25 or more days

• Raw Anomalies are unmasked for all events meeting criteria. Statistical significance determined by Monte Carlo test vs. random anomaly generation

Seasonal MJO Composites

• Darker color shades indicate strong statistical significance with little chance the anomaly is due to random chance. • Use as a check against model solutions when strong significance and active MJO phase are present

Current ENSO Status, Probabilistic Forecast for the Lower Missouri River Valley,

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