When forecasters were ahead of the theoreticians - the case of "downstream development"
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<p align="justify">Although now retired, I have for many years been the lucky recipient of this journal. I have seen many interesting articles dealing with operational forecasting, severe storms and flooding etc, but none about what is called "downstream development". During my time at ECMWF, lecturing on training courses, this topic was perhaps one of the most popular. "Downstream development" refers to the common occurrences of successive baroclinic developments, propagating eastward with a speed of 25-30°/day, like some sort of "domino effect". I learned about it from the forecasters at the Swedish Meteorological and Hydrological Institute (SMHI) when I started there in 1968. It fascinated me immediately. It made me realise how tomorrow's weather over Sweden was not only dependent on the arriving cyclone over the North Sea, but perhaps also of another cyclone, further upstream in the North Atlantic. When I joined the Met Ops Section at ECMWF in 1991 the mechanism of "downstream development" proved useful for tracing the origin of bad forecasts. The greatest trophy was when we once managed to trace a bad 7-day forecast to an erroneous radiosonde observation on the Kamchatka peninsula.</p>