The skill with which a coupled ocean–atmosphere model is able to predict precipitation over a range of time
scales (days to months) is analyzed. For a fair comparison across the seamless range of scales, the verification
is performed using data averaged over time windows equal in length to the lead time. At a lead time of 1 day,
skill is greatest in the extratropics around 408–608 latitude and lowest around 208, and has a secondary local
maximum close to the equator. The extratropical skill at this short range is highest in the winter hemisphere,
presumably due to the higher predictability of winter baroclinic systems. The local equatorial maximum
comes mostly from the Pacific Ocean, and thus appears to be mostly from El Nino–Southern Oscillation ~
(ENSO). As both the lead time and averaging window are simultaneously increased, the extratropical skill
drops rapidly with lead time, while the equatorial maximum remains approximately constant, causing the
equatorial skill to exceed the extratropical at leads of greater than 4 days in austral summer and 1 week in
boreal summer. At leads longer than 2 weeks, the extratropical skill flattens out or increases, but remains
below the equatorial values. Comparisons with persistence confirm that the model beats persistence for most
leads and latitudes, including for the equatorial Pacific where persistence is high. The results are consistent
with the view that extratropical predictability is mostly derived from synoptic-scale atmospheric dynamics,
while tropical predictability is primarily derived from the response of moist convection to slowly varying
forcing such as from ENSO.ous leads and for all the four seasons. While ACC remains high for fall, winter and spring seasons, the skill drops off markedly for summer at longer lead time. On the other hand, for DJF while ACC remains around 0.9 at all leads, S/N, a measure of the spread, drops off by a factor of ~ 2.7 (from 6.1 to 2.3).