The Great Floods of 1993 and 2008 : The Roles of ENSO and the MJO/GWO

Venice, Iowa (was Cedar Rapids)

NOAA 33rd Annual Climate Diagnostics and Predictability Workshop

Lincoln, Nebraska

October 20th, 2008

Edward Berry, NOAA/NWS DDC and Klaus Weickmann, NOAA/ESRL PSD

OUTLINE

The Global Wind Oscillation: Introduction

Schematic GWO/MJO phase spaces

ENSO precipitation signals for 1993 and 2008

GWO/MJO phase spaces during 1993 and 2008

May 22-26 case study: SNR 250 hPa PSI composites and potential predictability

Summary

Purpose is to examine the interannual-subseasonal relationships of the global atmospheric circulation that may have

contributed to the “great floods.”

The Global Wind “Oscillation”

Want:• > 1 region• monopole

L L

LL

H H

Models Struggle

Models Struggle

La-Nina El-Nino

19932008

La-Nina

El-NinoEl-Nino

La-Nina

GWO 2008

GWO 1993

June

JulyMay

June

Weak subseasonal variations.

Large subseasonal variations

MJO 1993

MJO 2008

June MayJuly

June

Weak subseasonal variations Large subseasonal

variations

Severe Local Storms/Heavy Rainfall May 22-26

Case Study

MJO GWO

Centered on 15 May

H H

HH

HH

H

H LL

L

L

LL L

H

HH

H

H

L L

WK-2: May 23-29

See May 10th and 15th blog postings for details

WK-2 GEFS

WK-2 CPC

WK-2 500mb Za OBS

WK-2 500mb Zt OBS

CPC

OBS

May 23-29 Air Temperature Anomaly Forecasts

Summary

Jun-Jul 1993 mean anomalies imply “flood”; May-Jun 2008 anomalies do not => suggests larger subseasonal role in 2008

“Synoptics” of these spring-summer central USA floods may be similar when ENSO decays rapidly and during a large subseasonal

oscillation

Real-time monitoring utilizing SNR composites for both the GWO and MJO offered ~week-2 forecast opportunities at times when

operational model predictions failed

250 hPa PSI SNR for tropics ~0.6-0.8σ versus ~0.2-0.3σ across the extratropics for both MJO and GWO => weak but useful signals

Questions ?