Ascension : Met Office Ascension Island Base - The Met Office Weather Report
Submitted by The Islander (Met Office) 30.04.2009 (Article Archived on 14.05.2009)
During May and June, the Southern Plains of the US will reach the peak of the tornado season.
Statistics for the week ending Monday 27th April 2009
|
|
Max (Celsius) |
Min (Celsius) |
Rainfall (mm) |
AIRHEAD |
31.3 |
25.2 |
1.5 |
|
TRAVELLERS |
31.5 |
24.0 |
1.5 |
|
GEORGETOWN |
32.4 |
23.8 |
0.5 |
|
ST. HELENA |
24.2 |
13.7 |
11.6 |
|
FALKLANDS |
12.2 |
0.8 |
14.9 |
|
UK(Brize Norton) |
19.0 |
3.3 |
6.0 |
“Toto, I don’t think we’re in Kansas anymore”
During May and June, the Southern Plains of the US will reach the peak of the tornado season. The plains make up a large part of ‘Tornado Alley’ which includes the states of Texas, Oklahoma, Kansas and Nebraska. On average, around 1000 twisters occur in the US every year, killing around 60 people. Oklahoma City holds the record for the city suffering the most ‘hits’, having now recorded a total of 100. Most tornadoes travel from Southwest to Northeast, and damage is very localised; sometimes, one side of a street may be destroyed, whereas the other remains relatively untouched. Tornadoes are graded using the Enhanced Fujita Scale (F0 to F5), which relates the intensity of the wind to the amount of damage caused. That which lifted Dorothy’s house in the Wizard of Oz would score an F5.
At this time of year, warm, moist air spreading up from the Gulf of Mexico is a good catalyst for brewing severe storms; however, very dry and warm air spreading east from the Rocky Mountains will act as an invisible lid in the atmosphere, suppressing any instability. Around late afternoon at maximum temperature, the lid may finally break, releasing huge amounts of energy, and allowing explosive development of large convective clouds. If conditions are right, Supercells may develop. These giant electric storms have rotation, and strong updraughts, which can aid the development of tornadoes and large hail. Severe hail in the States is defined as having a diameter greater than that of a dime, but hailstones up to baseball size are not uncommon.
Unknown to many, the UK has the highest frequency of reported tornadoes per unit area in the World; luckily though, most are small and don’t cause any major damage. There’s no place like home.
Wayne Bow
Met Office Ascension
Contact Met Office Tel 00247 3317
Email: ascensionstaff@metoffice.gov.uk
© Crown Copyright 2009
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