Niet van mij maar gepikt van het Engels forum
I have gathered together recently a full listing of variables that are needed to produce snowfall. If all the below criteria is met then it would be safe to say snowfall is a certainty. I stress however that some of the variables don't need to be present for snowfall to occur. A good example of this was the past week when even though many of the below variables weren't met snowfall still occured in the band of what was generally rainfall over the Southern uplands. This occured due to the general cooling and lowering of the freezing level in association with the heavy precipitation. Some of the variables present are difficult to find if you don't know how to use atmospheric soundings, but the 850mb temp, surface dew points, surface air temperature, 1000-500mb thickness, 1000-850mb thickness and 500mb temperatures can all be easily found with online information. The other information is available online, but again can only be found by using atmospheric soundings. Hope the below information is of use to many over the coming weeks and months. Any further questions, post away...
Matt.
• 850 hpa temperatures below -5 ºC
• Dew point surface temperatures below 0 ºC
• Surface air temperature less than 1.5 ºC (>2,0 ºC sleet more likely)
• Surface Wet bulb temperatures below 2 ºC
• Height of the 0 ºC isotherm less than 400m (roughly 1300ft)
• 1000-500mb thickness <523dam.
• 1000-800mb thickness <129dam. (>131dam usually rain, inbetween sleet).
• 850-700mb thickness <154dam. (>155dam usuall rain)
• 0C WBZ Temperature <1500 (>2000ft generall rain or possible sleet)
• Good vorticity, polar low, sharp trough, active front.
• (500mb temps below -35C in general, especially for Polar Low development)
Mr. Matthew Hugo, BSc(Hons)
Veel parameters zijn mij bekend maar wat betekent " 0C WBZ Temperature <1500 (>2000ft generall rain or possible sleet)" ?
Ook 1000-500mb-dikte <523 dam, ik denk dat 528 dam voldoende is.
Quote selectie