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Fig4.2-2:  Rapid growth of uncertainty (in the background forecasts of the Ensemble of Data Assimilations (EDA)) for PV on the surface where potential temperature=315K (shaded as scale).   Also shown are the CTRL forecast PV=2 on 315K (red contour) and 850hPa wind vectors, and ensemble mean precipitation (dots; size indicates rate).   Rapid growth of uncertainty can be associated with cyclogenesis and warm conveyor-belts.  Meso-scale Mesoscale convective systems (e.g. over USA) can also distort the upper flow significantly.  The ENS perturbations may not capture such rapid growth adequately and the upper flow may well become modified more than has been modelled with significant downstream differences at a later time in consequence.  It is helpful to note the development of energetic and fairly large convective systems or strong dynamic upslope motions in warm front conveyors and assess the possible impact on IFS performance.

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