Moderate Risk of Scattered Thundery Showers with Small Hail 11Z-20Z Thurs 12th April 12 East Eire & much of UK
Small Risk of Funnel Cloud Observations as per Yellow Box
A similar day to yesterday Weds, with a scattering of thundery showers for the said regions. Once again weak upper support and saturated mid and upper levels of the atmosphere will reduce the potential for any severe weather or organisation of convective cells. I have once again added a marker box for a small risk of funnel development with today's atmospheric conditions marginally superior to yesterday. Models predict better surface moisture with lift generated from closer to surface. A convergence zone is expected to develop through the afternoon along the South Downs and up into E Anglia. The risk for Funnel Clouds (as with yesterday) is forecast as 'Slight' in nature; This does not mean that FC's will occur but that it is deemed that there are conditions which are marginally conducive to their development! Though once again a lack of dry air within the lower mid levels reduces the risk somewhat for today. Interesting to note; that the presence of dry air above a layer of moist at the top of the boundary layer causes lapse rates to fall rapidly over a very short vertical height. This in turn increases the speed of an upward rising parcel and hence stronger updrafts are created at much lower levels. The congestus cloud may not necessarily develop any great height or thunder but may posses a strong low level updraft for a short duration. The only additional factor is moisture and dynamic lift that can push the rising parcel into its LFC with some level of vorticity available from below.
Red box indicates an approximate zone of a sharper converging surface vector regarding FCs
PS. anyone living around Colchester/ Ipswich your feedback regarding todays results, if any would be much appreciated!
This post has been edited by Tony Gilbert: 12 April 2012 - 08:04