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A) Local total growth rate (dashed) and relative amplification factor (thick solid) of FTPOP1 as functions of time starting and finishing on 15 January, (b) corresponding average local total growth rate (dashed) of five leading FTPOPs and relative amplification factor (thick solid) Fig. 8a shows two measures of the change with the annual cycle of the root mean square streamfunction amplitude of FTPOP1, the leading (least damped) empirical mode. The first is the local total growth rate, ω ˜ i1 (t) (dashed), the tendency of the logarithm of the amplitude, and the second is the relative amplification factor R1 (t) (thick solid), the ratio of the evolved to initial amplitudes (scaled by expωi1 t where ωi1 is the global or annual average growth rate).

4a of Dole10 ) is shown unfiltered 500hPa geopotential data for the perturbation on day -3 before the appearance on day 0 of a quasi-stationary large-scale positive anomaly in the key region in the north central Pacific; Fig. 4b (taken from Fig. 1f of Dole10 ) shows the corresponding low-pass filtered data for the mature anomaly on day 6. We note the (a) (b) Fig. 4. 10 broad similarities particularly in the Pacific-American region between the onset-of-blocking mode in Fig. 3a and the day -3 anomaly in Fig.

In these studies31 eight separate breeding cycles starting from 8 different perturbations over the first 10 days were performed. The self-breeding was also performed for 8 different perturbations with the ensemble forecast consisting of 16 forecasts employing the 8 initial bred perturbations and 8 initial identical perturbations with opposite signs. This ensures that April 25, 2007 12:18 WSPC - Proceedings Trim Size: 9in x 6in newmaster 44 the ensemble mean forecast starts from the same initial condition as the control.