1. Synoptics and May 2003 tornado outbreak Indian Ocean forcing
Can we produce low-frequency indices as in the case study?

2. L H L H L L H L H L L H L H L H L H L H L 28 April 2003
25 Apr - 1 May 2003 L H L H L
29 April 2003
26 Apr - 2 May 2003 L H L H L L H L
28-30 April 2003
30 April 2003
27 Apr - 3 May 2003 H L H L H L H L

3. H L L H L L H H H H L L L H H L L L H H H L H L H L L H L H H H L L H
4 May 2003
1-7 May 2003 H L L H L L H H H H L L
5 May 2003
2-8 May 2003 L H H L L L H H H
4-6 May 2003
Alternate interpretations: constructive interference of RWD events; RWD caught up in flow and baroclinic development L
6 May 2003
3-9 May 2003 H L H L L H L H H H L L H

4. H H L L L H L H H H L L H H H H L L L H H L L H H H L H L H L H L H L
7 May 2003
4-10 May 2003 H H L L L H L H H H L L H
8 May 2003
5-11 May 2003 H H H L L L H H L L H
7-9 May 2003
The H/L over the nOrth Pacific is shifted west relative to January 2002.
Two possible interpretations for the growth of the ridge: 1) Rossby Wave wavetrain interacts with the storm track or 2) constructive interference of multiple RW wavetrains.
9 May 2003 H H L H L H L H L H L H

5. H L H L H L H H L L H H H L L L L H H L L L L H H L H H H L L H 1-15
May
2003
16-31 H L H L H H L L H H H L L L L H H L L L L H H L H H H H
250mb vector wind anomalies for 1-15 May 2003 (top) and May 2003 (bottom). Point is to illustrate a near reversal of circulation anomalies across the PNA sector as the tropical convective forcing shifted from the IO into the WPac. This change can be captured with roughly sub-monthly averaging due to the time-scale of the forcing; in this case, the MJO. I guess there needs to be a distinction between an “instantaneous space average” verses averaging a coherent temporal behavior such as the MJO and the circulation response. In this type of case (MJO, etc.), instantaneous spatial averages for a specific period of time (15 days) are needed to define a relatively coherent temporal evolution that spans a longer period such as intraseasonal. The point is that there is overlap and daily monitoring is needed whatever the case may be. L L H
250mb Vector Wind Anomalies