SLIGHT RISK of Convective Rainfall & localised Flooding
A SLIGHT RISK of Excessive convective Rainfall has been issued for parts of South West, and Southern England. A WATCH covering much of Southern England including parts areas NW of London into the East Midlands. An attendant non-convective rainfall watch has been issued for the potential of persistent rainfall and localised flooding in the North. Elsewhere rainfall will generally be below the required threshold fo...

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Met-Monkey Atlantic Storm Naming Convention: Season 2010/2011

What’s it all about?

The new Atlantic Storm Naming Convection will be adopted by Met-Monkey commencing the 2010 season. So that’s right about now. The idea is a relatively new concept, already adopted by the Berlin Institute of Meteorology.

Every year several Atlantic Depressions and Storms develop in the Western Atlantic approaches and trundle towards Europe. The naming convention will be put in place to identify depressions or storms that pose a significant threat to these European countries in terms of excessive rainfall and damaging wind swathes.

By naming a depression or storm when it meets a certain threshold requirement, we can give you a much clearer idea on the type of storm involved, where the storms location is and in what direction it is travelling. It makes it easier to identify several depressions or storm systems at once.

How Does it Work?

We have introduced 3 major weather systems. First off these are:

Major Atlantic Depression
Atlantic Storm
Major Atlantic Storm

Assigned to these 3 major weather systems are basic meteorological criteria to be satisfied.

Major Atlantic Depression

To constitute a depression the area of LOW pressure must have a reasonable pressure core and a steady barometric drop. Isobars will be tight and sustained winds will be projected at F9 (Severe Gale) on the Beaufort Scale or 45mph+, further requirements are wind gusts that are locally damaging in the range of 60 – 70mph. Although rainfall is always associated with areas of deepening low pressure, the threshold for rainfall will vary although any values over 25mm in a 6 hour period is considered an average and reasonable expectancy.

Typical Dangers associated with Major Atlantic Depressions:

Difficulty Walking in exposed areas
Minor damages to property
Minor Disruption to transport networks
Localised uprooting of trees & minor tree damages
Localised Flooding

Atlantic Storm

To constitute the naming of an Atlantic Storm the area of LOW pressure must undergo a rapid rate of intensification. Technically referred to as rapid cyclogenisis. Isobars will be tight around most of the gradient immediately around the centre of the LOW. Sustained winds will be projected at F9 (Severe Gale) or locally F10 (Storm Force) on the Beaufort Scale or 45 – 53mph, further requirements are wind gusts that are damaging in the range of 70 – 90mph. Excessive rainfall is likely for some regions with over 25mm a reasonable expectancy, locally a lot more depending on the type of storm.

Typical Dangers associated with Atlantic Storms CAT 1 to CAT2

Impossible and dangerous to walk in exposed areas
Difficulty Walking in less exposed areas
Major Disruption to transport networks
Disruption to Power utilities
Uprooting of trees and locally major tree damages
Risk of fatalities from falling trees, damage to buildings including roof tile and wall failures
Localised to perhaps significant flooding
Significant coastal flooding a possibility

Major Atlantic Storm

To constitute the naming of a Major Atlantic Storm the area of LOW pressure must undergo explosive intensification accompanied by a very low barometric pressure reading. These storms almost always develop sting jets that form as a result of dry air being sucked into the baroclinic leaf region aiding in the lowering to sea level of the jet-stream winds. These storms are not only dangerous, they can bring widespread devastation. Technically referred to as explosive cyclogenisis or bombogenisis. Isobars are often extremely tightly packed around the core with sustained winds projected at F10 to F12 (Storm Force to Hurricane Force) on the Beaufort Scale or 53 – 74mph, further requirements are wind gusts that are damaging to devastating in the range of 90 – 120mph+. Excessive rainfall is usually a common feature, as well as severe thunderstorms and tornadoes. Due to the very low barometric pressure asserting a lot more force on the ocean, during high tides these storms will bring devastating and extreme coastal flooding.

Typical Dangers associated with Major Atlantic Storms CAT 3 to CAT 5

Impossible and extremely dangerous to walk in exposed areas
Very difficult to walk to locally impossible in less exposed areas
Major to devastating disruption to transport networks
Severe Disruption to power utilities, in extreme circumstances power loss for days
Widespread uprooting of trees
High risk of fatality from falling trees, major structural damage to buildings including complete roof and wall failure
Localised to perhaps significant flooding
Potentially devastating coastal flooding
Severe thunderstorm bring the additional threat of large hail, damaging winds and tornadoes
Locally widespread devastation is possible on higher CAT 4 and 5

Categorical Storms?

Like hurricanes that form in the summer and early autumn season in the Atlantic and Gulf of Mexico, we’ve decided it would be prudent to not only name the storms and class them as Major Depression, Atlantic Storm and Major Atlantic Storm; but take it a step further and follow our American cousins in assigning a well known Category Scale from 1 to 5. 1 meaning the lowest intensity and 5 the highest. This will help us become more aware of the dangers that higher category storms can bring. That’s the theory anyway.

Below you will see more detailed explanations of the categories and what each one means for you.

Category 1 Atlantic Storm

Considered a minor storm, but slightly stronger wind gusts than a Major Depression and more capable of producing damages to your property. This storm still needs to be taken seriously.