Tahiti, Darwin, and pressure oscillations

SOI = Tahiti - Darwin (normalized)

Niño Region SST Departures ( o C) Recent Evolution The latest weekly SST departures are: Niño ºC Niño ºC Niño ºC Niño ºC

SOI and Nino 3-4 index

Sea surface temperature: total and deviation from average

Historical El Niño and La Niña Episodes based on the ONI computed using ERSST.v3 NOTE: After upgrading the ocean analysis to ERSST.v3, the following weak ENSO episodes no longer meet the NOAA criteria for an ENSO episode: El Nino: FMA 1993-JJA 1993 La Nina: ASO 1961-MAM 1962 ASO DJF 1983/84 Highest El Niño ONI Value Lowest La Nina ONI Value JAS NDJ 1951/ MAM 1957 – MJJ ASO 1949 – FMA MAM 1954 – DJF 1956/ JJA 1963 – DJF 1963/64 1.0MAM 1964 – JFM MJJ 1965 – MAM NDJ 1967/68 – MAM OND 1968 – MJJ JJA 1970 – DJF 1971/ ASO 1969 – DJF 1969/70 0.7AMJ 1973 – JJA AMJ 1972 – FMA ASO 1974 – AMJ ASO 1976 – JFM SON 1984 – ASO ASO JFM AMJ 1988 – AMJ AMJ 1982 – MJJ ASO 1995 – FMA ASO 1986 – JFM JJA 1998 – MJJ AMJ 1991 – JJA SON 2000 – JFM JJA 1994 – FMA AMJ 1997 – MAM AMJ 2002 – FMA JJA 2004 – JFM JAS DJF 2006/07 1.2

ONI time series (part 1)

ONI time series (part 2)

NH winter rain: Normal, El Nino, La Nina Normal La Nina El Nino Colors: greater than 8, 10, 12 mm/day

Climatological DJF 500mb Heights

NH winter 500mb height deviations from zonal average: Normal, El Nino, La Nina Normal La Nina El Nino Stronger jet Eastward shift of PNA pattern +

El Nino global response (NH winter anomalies) SST and rainfall 250 mb height Rainfall anomaly max = 5 mm/day

La Nina global response (NH winter anomalies) 250 mb height SST and rainfall

Global response (NH winter anomalies) El Nino La Nina

Storms are guided by the jet stream

DJF Climatological Storm Tracks

Climatological Storm Tracks (ct’d) DJF JJA

Jet stream configur- ations

Global Effects

Mean number of days per season (November - March 1948 through 1993) in which precipitation exceeded 0.50 inches for Neutral years (top). Lower left map is the difference in this quantity between El Niño years and Neutral years. Lower right map is the difference in this quantity between La Niña years and Neutral years. North American Effects

(Some Extra Slides Follow)

Central & Eastern Pacific Upper-Ocean (0-300 m) Weekly Heat Content Anomalies Since January 2007, the upper ocean heat content has been below average across the eastern half of the equatorial Pacific Ocean. Below average heat content favors the continued development of La Niña. Intraseasonal variability during May - August 2007 is related to the MJO.

SST Departures ( o C) in the Tropical Pacific During the Last 4 Weeks During the last four weeks, equatorial Pacific SSTs were more than 1ºC below average east of the Date Line and more than 2ºC below average east of 135 o W. SSTs remained more than +0.5 o C above average between 130ºE and 150ºE.

Recent Evolution of Equatorial Pacific SST Departures ( o C) Longitude Time Over the past several months, below average SSTs have expanded westward and negative anomalies now cover most of the equatorial Pacific Ocean. The SST anomalies decreased rapidly in January 2007 everywhere east of the Date Line.

The monthly thermocline slope index represents the difference in anomalous depth of the 20ºC isotherm between the western Pacific (160ºE-150ºW) and the eastern Pacific (90º-140ºW). Upper-Ocean Conditions in the Eq. Pacific The basin-wide equatorial upper ocean (0-300 m) heat content is greatest prior to and during the early stages of a Pacific warm (El Niño) episode (compare top 2 panels) and least prior to and during the early stages of a cold (La Niña) episode. The slope of the oceanic thermocline is least (greatest) during warm (cold) episodes. Current values of the upper-ocean heat anomalies (negative) and the thermocline slope index (positive) indicate La Niña. Cold Episodes Warm Episodes

ONI ( o C): Evolution since 1950 The most recent ONI value (August – October 2007) is -0.8 o C. El Niño La Niña neutral