| Welcome to Natural Hazards Forum. We hope you enjoy your visit. You're currently viewing our forum as a guest. This means you are limited to certain areas of the board and there are some features you can't use. If you join our community, you'll be able to access member-only sections, and use many member-only features such as customizing your profile, sending personal messages, and voting in polls. Registration is simple, fast, and completely free. Join our community! If you're already a member please log in to your account to access all of our features: |
| Thunderstorms and Convection. By Matt Hugo October 7, 2014 | |
|---|---|
| Tweet Topic Started: 7 Oct 2014, 03:06 PM (14 Views) | |
| Audi-Tek | 7 Oct 2014, 03:06 PM Post #1 |
|
Thunderstorms and Convection. By Matt Hugo October 7, 2014 Thunderstorms and Convection OVERVIEW: Some of you may have noticed that some of the showers in the last day or so have been particularly heavy with rumbles of thunder and also some hail as well. That overall risk of heavy showers and possible thunderstorms will continue. This isn’t unusual given the unsettled conditions, but the primary cause of the thunderstorms is different to that of during summer and we thought we would highlight the primary reason why. ANALYSIS: Low pressure, as we discussed within the weekly analysis, is well and truly dominating the weather this week and this unsettled regime is highlighted well on the below water vapour image with 500mb heights overlaid; ![]() A large upper vortex with various areas of low pressure at the surface is dominant over and to the west of the UK. What is of importance on this image is the white speckled pattern over Ireland, near SW England and to the west of the UK in general. This is instability within the atmosphere and numerous areas of heavy showers and thunderstorms. One of the obvious questions is? Why are thunderstorms forming over water when in summer they form over land? Well the primary reason for this is due to the time of year now. To get instability within the atmosphere, and when I say instability I mean large towering clouds that can produce heavy downpours and thunder, you need colder conditions within the mid and upper atmosphere to be sitting over warmer conditions within the lower atmosphere. Usually during summer this occurs over land because surface temperatures over a land mass warm considerably in the strong summer sunshine and thus you get warmer temperatures at the surface and cooler temperatures aloft which help to create instability. During the autumn and winter months this process is reversed. Because the air mass over the UK at the moment is particularly cool and given the time of year, it is the sea surface temperatures that are high enough to create the instability and not necessarily the land. This is why within the last 24 hours heavy and thundery showers have been filtering into more southern and western areas of the UK off the North Atlantic and that risk will continue in the coming days. This instability is represented well on the 10KM resolution model which clearly shows a greater level of instability over the nearby ocean, which again ties in with what has just been discussed. The green colours on this image highlighting the regions at greatest instability and as can be seen that instability is greatest near to Ireland and SW England and it is across these areas of the UK that heavy showers and thunderstorms have been in evidence; ![]() With low pressure sitting over the UK or just to the west in the coming days then this risk of some heavy downpours and thunderstorms will continue for parts of the UK. At the moment the risk is likely to be greatest across southern and western areas of the UK including; The Midlands, S England, SW England, Wales and Ireland. A few heavy showers and thunderstorms may develop over land in the coming days as temperatures recover a little compared with the cold start to the week, but otherwise the heaviest and most frequent showers will continue to affect areas near to the warmer sea temperatures just to the west and south-west of the UK. Source Info: eumetrain.org Link.............. http://www.ukweatherforecast.co.uk/thunderstorms-convection/#sthash.fhmdMBCF.dpuf |
![]() |
|
| 1 user reading this topic (1 Guest and 0 Anonymous) | |
| « Previous Topic · Weather chat · Next Topic » |








8:09 PM Jul 11