Overview

• Northern hemisphere extra-tropics

• El Niño

Seasonal Climate – Winter 2009-10

Mike Blackburn

Seasonal Climate Discussion, 14 April 2010

Winter in the UK DJF averages

Reading: Tmax, Tmin DJF 0910

Temperature

• Mean 1.6°C

• 2.1°C below 1971-2000 average

Precipitation (%)

• Total 249mm

• 75% of average

Mike Stroud

European anomalies - DJF

NOAA Climate Prediction Center

Temperature Precipitation (% normal)

Surface air temperatureDecember 2009 January 2010 February 2010

DJF average

• Persistence

• Warm Arctic + sub-tropics

NOAA ESRL

Westerly winds – DJF climatology

U 250hPa U 850hPa

NOAA ESRL

U 250hPa U 850hPa

NOAA ESRL

Westerly winds – DJF 2009/10

U 250hPa U 850hPa

NOAA ESRL

Westerly winds – DJF 2009/10 anomalies

Percentage of days with significant anomaly of same sign (>15m)

Z500 – persistence….

NOAA Climate Diagnostics Bulletin

Persistence

(%)

December 2009 January 2010 February 2010

Monthly Mean

(dm)

First month for which 60% anomaly correlation reached 10 days for Europe and northern hemisphere

…and February forecast skill

www.ecmwf.int

Arctic Oscillation (AO)

North Atlantic Oscillation (NAO)

Z500

PMSL

PMSL anomaly

NCEP reanalysis DJF 2009/10

Z500 anomaly

NAO and AO time-series

NOAA CPC DJF average

Arctic Oscillation (AO)

North Atlantic Oscillation (NAO)

Z500

PMSL

El Niño

NOAA ESRL

SST anomaly DJF 09/10

OLR anomaly DJF 09/10

NOAA Climate Diagnostics Bulletin