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Weather Word Wednesday : Nor’easter

January 12th, 2011 No comments

I just read a Twitter post from @reedtimmerTVN that said another Nor’easter was bearing down on the East Coast of the United States today. It occurred to me that I really don’t know what a Nor’easter is, so I figured that would be the perfect word for Weather Word Wednesday.

According to Wikipedia, a Nor’easter is “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, especially in the coastal areas of the Northeastern United States and Atlantic Canada.”

Specifically, a Nor’easter describes a low pressure area who’s center of rotation is just off the East Coast and who’s leading winds in the left forward quadrant rotate onto land from the northeast. Nor’easters can cause coastal flooding, coastal erosion, hurricane force winds and heavy snow. While they can occur at any time of the year, they are most frequent in the winter months. These systems are known for bringing down extremely cold arctic air from the north.

Satellite image of the intense nor'easter responsible for the North American blizzard of 2006. Note the hurricane-like eye at the center.

Nor’easters generally affect the United States, from Virginia to the New England cost, as well as Quebec and Atlantic Canada. They tend to bring massive amounts of precipitation, high winds, large waves, and marginal storm surges to coastal areas. In general, though, people tend to call any strong rain or snow storm in the Northeast a Nor’easter. The very name brings feelings of dread and anticipation to people in the region!

For more information, visit this Wikipedia article on Nor’easters.

Water Vapor Imagery

August 24th, 2010 No comments

I recently “discovered” on the local NWS website the Satellite Water Vapor Imagery data for our area, and I’m quite fascinated by it! The official description of this data is as follows:

Water vapor satellite imagery depicts moisture content in the middle and upper layers of the atmosphere. Lower level moisture is not depicted in these images. Moisture transport over large distances generally happens through the middle and upper layers of the atmosphere. Hence these images will depict moisture coming into the Southwest from the Gulf of Mexico or across Texas. Additionally, weak disturbances from the east are best tracked through water vapor imagery.

The imagery looks like this when viewed online. The is a screen capture of one frame of data:

Water Vapor Imagery

Water Vapor Imagery

Basically, what this shows is the amount of moisture that is in the upper atmosphere. This may be in the form of clouds that you see, but often it is not. Water vapor literally surrounds the earth, but is unevenly distributed due to things like oceans, lakes, rivers, deserts, arid areas, etc. For instance, in the image above, you can see a lot of water vapor coming up from the southwest into places like Arizona and New Mexico, which are traditionally dry regions. Areas like the Pacific Northwest, which are usually wet, have much less than normal. This is all due to seasonal shifts in winds and weather patterns, which change the flow of moisture around the planet. By looking at an image like this, you can get an idea of how much moisture is available in your area…moisture that could turn to rain or snow!