Max (Celsius)	Min (Celsius)	Rainfall (mm)
AIRHEAD	32.0	25.1	Trace
TRAVELLERS	33.4	20.6	Trace
RESIDENCY	29.1	20.6	Trace
GEORGETOWN	n/a	n/a	n/a
ST. HELENA	26.2	19.7	15.6
FALKLANDS	22.0	2.3	28.1
UK (Brize Norton)	12.3	-0.6	0.4

UK: The week dominated by high pressure over the UK with mainly dry, fine weather. Some quite sunny days, but with clear nights some frost as well. A little rain at times for northern Scotland.

Falklands: Some fine warm days early in the week. Unsettled and much cooler with rain late in the week and over the weekend.

Ascension: No records broken, but the temperature remains a degree or two above average as the mostly fine sunny weather continues. Only halfway through the month, but so far very little if any rain.

St Helena: Mainly dry with sunny spells. A few rain showers though, the more frequent and heavier of these early in the week.

***************

Georgetown Dust Devil

Dust Devils are not exactly rare on Ascension Island, fairly frequently occurring around Georgetown, on Donkey Plain, Broken Tooth Range, or in fact anywhere on the west and northwest side of the island.

A Dust Devil is a strong and well formed whirlwind. Whirlwinds can occur anywhere given the correct conditions, generally in hot sunny weather with a relatively light breeze. They are called “Dust Devils” because, as the name implies, they pick up dust and become visible. Most are fairly harmless, and soon dissipate, though a few can become quite large with strong rotating winds of 45mph or more.

One particular dust devil in Georgetown last Thursday was notable, because it was large and powerful enough to damage some property, i.e. at least one garage roof.

Dust devils form when hot air near the ground rises quickly into cooler, low pressure air above. Given the right conditions the air begins to rotate and through “conservation of momentum” this spinning effect can be significant if the plume of rising air is large and powerful enough.  The dust devil can begin to move forward by itself due to the spinning effect, though they often move in the direction of the prevailing breeze.

Now which way does the vortex of the whirlwind, dust devil, spin?  Given it is a “low pressure area” it should, in the southern hemisphere, spin clockwise; (this would be anticlockwise in the northern hemisphere). There are reports that this one was spinning anticlockwise.  It is possible this was an illusion as blowing debris and dust from the outflow was deflected around buildings?

In other parts of the world dust devils can have local names. These include; “dancing devil” in the Southwest USA, and the Navajo Indians refer to them as chiindii – meaning ghosts or spirits of the dead.  There are many other local names, but the one I like is from Australia, the “willy-willy”.

Compiled by  Chill       

Crown Copyright 2010        Met Office Ascension Island Base