El Niño and the

Southern Oscillation

(“ENSO”)

“Normal” SST

Walker circulation

ps(hPa)

Correlations (×10) of fluctuations in annual mean

sea level pressure with those at Darwin. The

magnitude of the correlation exceeds 0.4 in the

shaded regions. (After Trenberth and Shea, 1987.)

Cx0 ,x p x 0,tp x,t

p 2x 0,t p 2x,t

1880 1890 1900 1910 1920-40

-30

-20

-10

0

10

20

30

40

so

i

1920 1930 1940 1950 1960-40

-30

-20

-10

0

10

20

30

40

so

i

1960 1970 1980 1990 2000-40

-30

-20

-10

0

10

20

30

so

i

soi

Southern Oscillation Index 1880-2000

SOI 10 SLPTahitiSLPDarwin

1880 1890 1900 1910 1920-40

-30

-20

-10

0

10

20

30

40

so

i

1920 1930 1940 1950 1960-40

-30

-20

-10

0

10

20

30

40

so

i

1960 1970 1980 1990 2000-40

-30

-20

-10

0

10

20

30

so

i

soi

Southern Oscillation Index 1880-2000

SOI 10 SLPTahitiSLPDarwin

“Normal” SST

Walker circulation

“Normal” SST

Sea surface temperature anomalies (C)

0 – 10S, 80 – 90W

1950 1955 1960 1965 1970 1975-4

-3

-2

-1

0

1

2

3

4

SO

I, S

ST

an

om

aly

(K

)

1975 1980 1985 1990 1995 2000-4

-3

-2

-1

0

1

2

3

4S

OI,

SS

T a

no

mal

y (

K)

SST anomalies (Nino 1+2)

vs SOI

SOI

SST

Annual rainfall (in percentiles) in a selection of

regions. Black bars coincide with "El Niño" years.

cold

warm

cold

warm

Correlations (×10) of fluctuations in annual mean

sea level pressure with those at Darwin. The

magnitude of the correlation exceeds 0.4 in the

shaded regions. (After Trenberth and Shea, 1987.)

Cx0 ,x p x 0,tp x,t

p 2x 0,t p 2x,t

El Nino impacts in U.S. winter

2015 El Nino

SST, OLR now

Niño Region SST Departures

(oC) Recent Evolution

The latest weekly SST

departures are:

Niño 4 1.4ºC

Niño 3.4 1.0ºC

Niño 3 1.0ºC

Niño 1+2 1.9ºC

Sub-Surface Temperature Departures in the Equatorial

Pacific

Most recent pentad analysis

Recently, negative anomalies in the eastern Pacific

have dissipated, while they have increased at depth

in the western Pacific.

During the last two months, positive subsurface

temperature anomalies increased at depth in the

eastern Pacific.

Outgoing Longwave

Radiation (OLR) Anomalies

Drier-than-average Conditions (orange/red shading)

Wetter-than-average Conditions (blue shading)

During November- mid January, positive

OLR anomalies were observed near the

Date Line.

During early March, negative OLR

anomalies shifted from Indonesia to the

Date Line.

Since mid March, positive anomalies

have been evident near Indonesia, while

negative anomalies have persisted near

the Date Line.

Tropical OLR and Wind

Anomalies During the Last

30 Days Negative OLR anomalies (enhanced convection

and precipitation) were evident near the Date

Line. Positive OLR anomalies (suppressed

convection and precipitation) were located over

the far western Pacific.

Weak, anomalous low-level (850-hPa) westerly

winds were located in the central and east-

central Pacific.

Anomalous upper-level (200-hPa)

easterlies were observed over the central

and east-central Pacific. An anomalous

anti-cyclonic couplet straddled the

equator over the central tropical Pacific.

A

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