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Day 362: Global perspective

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Peter Gibbs Peter Gibbs | 09:00 UK time, Wednesday, 28 December 2011

(Peter Gibbs is a BBC weather forecaster and appears as an expert meteorologist on "The Weather Show" for the BBC News channel. He started his first guest blog post for 23 degrees with 'What would happen if the Earth spun the other way' and provided much food for thought with his post on 'Abundance in fruits indicator to past British weather'. His post on 'What's in a name' cleared some misunderstandings that where flying around the web as remnants of hurricane Katia stirred it's way to the UK, and he provided us with a breakdown of the difference between cyclones, typhoons and hurricanes with his post on Cyclone Yasi. Keep up to date with Peter Gibbs - @peterg_weather)

Setting Sun on Earth's Horizon Framed by Solar Array Panels

Copyright: United States Government works

Distance travelled ~ 929'745'600 km

It may seem surprising, but weather forecasters need to take a rather parochial view of the world. At an airport, the forecaster has to predict cloud base, visibility, wind speed and direction in great detail over a few hours for a very specific location. Even a forecaster with a national brief will tend to concentrate only on the weather systems moving across that country and give no more than a passing glance to the storm spiralling across neighbouring areas.

One of the advantages of working as a weather broadcaster on BBC World is that I get to see the whole picture and can begin to understand the interactions of the global weather system with its regular seasonal pulse. A group of thunderstorms produces newsworthy rainfall as it tracks westwards across equatorial Africa, grows into a hurricane over the tropical Atlantic to threaten east coast America, then gets caught up by the jetstream and races across the north Atlantic to bring rain and gales to northwest Europe, passing through several forecast jurisdictions en route.

Other rhythms overlay the annual one. Swings from El Nino to La Nina take place over periods of several years and enhance or diminish normal seasonal features, especially rainfall. 2011 has been mostly a La Nina year,

attack of la nina ski movie

Copyright: MSP

with unusually warm water washing into the western side of the Pacific. The extra atmospheric moisture this provided was the likely cause of January deluges in Sri Lanka and the Philippines, as well as the extraordinary flooding in Queensland where an area the size of France and Germany was underwater for a time.


Continental landmasses tend to produce the biggest temperature contrasts and hence the most violent weather, especially during the transitional periods of spring and autumn. April 2011 was a record month for tornadoes in the USA with an estimated 600, smashing the previous April record of 257 and even beating the all time monthly record of 542, set in May 2003. Arctic air pushed further south than usual, meeting air from the exceptionally warm waters of the Gulf of Mexico and combining with a jetstream pushed unusually far south by La Nina.

As the Atlantic warmed, an active hurricane season was expected and the predictions were spot-on with a total of 19 named storms, of which seven became hurricanes including three major hurricanes of category 3 or above. Surprising then, that we had to wait for a record eight tropical storms to come and go before our first hurricane. But once formed, hurricane Irene made the biggest impact, passing through the islands of the northern Caribbean before becoming the first landfalling hurricane in the USA since 2008.

La Nina was in the dock again as the likely culprit when weeks of heavy rain produced some of the worst floods on record in Thailand. The monsoon season started early and finished late, meaning there were even greater volumes of water than usual flowing from the mountainous north to the low-lying plains of the south.

Having a global perspective makes me even more appreciative of our UK climate. The British Isles are at the crossroads of European weather. Atlantic winds are a moderating influence, while the proximity of continental Europe can provide bigger swings from hot to cold. Last December found me gliding on Nordic skis across the snowfields of Berkshire, while this December the Christmas journeys to friends and family will be easier on roads kept clear of snow and ice by mild westerlies. There is the excitement of the occasional mid-latitude depression or summer thunderstorm, but without the devastation of hurricanes and monster tornadoes.

Meteorological variety without the jeopardy. If you have to be a parochial forecaster, the UK isn't such a bad place to be.


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