Science 10 Mr. Jean May 7 th, 2012

The plan: Video clip of the day Predicting the perfect snow day –Types of storms –Timing –Public Opinion Powerful Planet – Atmosphere –(Last 30 minutes)

Types of storms: Nor’Easter The Blizzard Alberta Clipper The Snow day.

The Nor’easter

What is a Nor’easter? Nor'easter (also northeaster; see below) is a type of macro-scale storm along the East Coast of the United States and Atlantic Canada, so named because the storm travels to the northeast from the south and the winds come from the northeast. The storm has characteristics very similar to a hurricane.

Most nor'easters start from a low-pressure system that forms in the south, most often the Gulf of Mexico, and are drawn across to the Northeast by the Jet Stream. –Tracks Northeast and heads up along East Coast past the mid-Atlantic and New England coastal states.

The counterclockwise flow around a low-pressure system brings the warm moist oceanic air over land. The warm moist air meets cold air carried southward by the trough. –The low enhances the surrounding pressure gradient, which acts to spiral the very different air masses toward each other at an even faster rate. –The greater the temperature differences between the two air masses the greater the turbulence and instability, and the more severe the storm can become.

Conditions most favourable for a snow day. Nor’Easter –Significantly cold temperature. –High wind speeds –Start time around midnight –Continues into the day without decreasing in intensity until mid-day. – Probability: 75-90% for a snow day.

The Blizzard: A blizzard is a severe snowstorm characterized by strong winds.

The Blizzard: By definition, the difference between blizzard and a snowstorm is the strength of the wind. To be a blizzard, a snow storm must have sustained winds gusts that are greater than or equal to 56 km/h with blowing or drifting snow which reduces visibility to 400 meters or less Must last for a prolonged period of time — typically three hours or more

The Blizzard: Blizzards can bring near-whiteout conditions, and can paralyze regions for days at a time. A significant range of snowfall can occur. Generally a typical East Coast Blizzard will have 20-45cm of snow associated with it.

Conditions most favourable for a snow day. Blizzard: –Significantly cold temperature. –Occurrence during commute –Significant snow fall associated with Blizzard. – Probability: 90-95% for a snow day.

Iran Blizzard of 1972 The Iran Blizzard of February 1972 resulted in the deaths of approximately 4,000 people. A week-long period of low temperatures and winter storms, lasting from February 3 to February 9, 1972, dumped more than ten feet of snow across rural areas in northwestern, central and southern Iran. Southern Iran sustained as much as 26 feet of snow, burying at least 4,000 villagers.

The Alberta Clipper

The Alberta Clipper: An Alberta clipper is a fast moving low pressure area which generally affects the central and Atlantic provinces of Canada and parts of the Upper Midwest, Great Lakes and east coast regions of the United States. Most clippers occur between December and February, but can also occur occasionally in the month of November.

How it’s formed: Originates when warm, moist winds from the Pacific Ocean come into contact with the mountains in the provinces of British Columbia and then Alberta. Travels off of the mountains, then develops into a storm over the Canadian prairies when it becomes entangled with the cold air mass that normally occupies the region in winter. The storm then slides southward and gets caught up in the jet stream, sending the storm barrelling into central and eastern areas of North America.

Properties of an Alberta Clipper: The clippers, when reaching the Atlantic seaboard can cause a weather 'bomb' by trapping the Atlantic coast’s moisture close to shore. This results in larger snowfall amounts which can approach 6"-12" or more.

Conditions most favourable for a snow day. Alberta Clipper: –Storm must begin between 10pm and 2am. –Weather “Bomb” must develop to ensure large snowfall. –With temperature below zero this storm pattern can cause a snow day. –Strong winds. –Only a 50 to 80% probability of snow day if those conditions are met.

Big Time Snow!

Links to snowfall: ationpress/tag/snow/ ationpress/tag/snow/

BBC – The Atmosphere