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Great Blizzard pounding Chicago; extremely dangerous Cyclone Yasi nears Australia

By: Dr. Jeff Masters, 1:31 AM GMT on February 02, 2011

The Great Groundhog's Day Blizzard of 2011 is wreaking havoc tonight from Texas to Michigan, and is poised to spread dangerous winter weather eastwards to New England during the day Wednesday. Four states have declared states of emergency—Oklahoma, Missouri, Illinois, and Kansas—and the National Guard has been called out in Illinois and Missouri. Up to 1/2” of ice has caused power outages in Indianapolis, and blizzard conditions have engulfed Chicago, where heavy snows of up to two inches per hour are falling in high winds. Winds tonight at Chicago's Calumet Harbor were tropical storm force, 39 mph, with gusts to 49 mph. Winds gusts of 60 mph were occurring at the Chicago buoy, 10 miles offshore in Lake Michigan.

The storm will probably be Chicago's biggest blizzard since January 2 - 4 1999, when a storm dumped 21.6" of snow. With tonight's snowstorm expected to have very unstable air aloft, "thundersnow" with snowfall rates of 4 inches/hour is possible, and there is a chance today's blizzard could rival Chicago's greatest snow storm of all time, the blizzard of January 26 - 27, 1967. That immense storm dumped 23 inches of snow on Chicago, stranding thousands of people and leaving an estimated 800 Chicago Transit Authority buses and 50,000 automobiles abandoned on the city streets and expressways. Twenty six Chicagoans died in the blizzard, mostly due to heart attacks from shoveling snow. Strong winds in Chicago today are expected to generate 14 - 18 feet waves on Lake Michigan, with occasional waves up to 25 feet. A significant coastal flooding event is possible for the city, with beach erosion and flooding along Lake Shore Drive. I'll have a full update on the great blizzard in the morning.

Figure 1. Satellite image of the Groundhog's Day Blizzard of 2011, taken at 8pm EST February 1. Image credit: NASA/GSFC.

Category 4 Tropical Cyclone Yasi nearing Queensland, Australia
Tropical Cyclone Yasi continues to intensify as it speeds westwards towards vulnerable Queensland, Australia. Yasi, now a Category 4 storm with 140 mph winds, is under light wind shear of 5 - 10 knots, and over record warm ocean waters of 29°C (84°C). Low wind shear, record warm sea surface temperatures, and favorable upper-level outflow should allow the cyclone to maintain Category 4 strength until landfall Wednesday evening (local time.)

The Austrailian Bureau of Meteorology had this to say about Yasi in their latest advisory:



On Wednesday morning at 9:30am local time, Yasi hit tiny Willis Island, where a minimum pressure of 938 mb and a peak wind gust of 115 mph was observed before Yasi cut communications and damaged the radar.

Queensland faces three major threats from Yasi. The cyclone will bring torrential rainfall to a region with saturated soils that saw record flooding earlier this month. The latest rainfall rates in Yasi's eyewall as estimated by microwave satellite imagery are 20 mm (0.8") per hour. The GFS model is predicting that a wide swath of Queensland will receive 5 - 10 inches of rain over the next week, due to the combined effects of Yasi and a moist flow of tropical air over the region. Fortunately, Yasi is moving with a rapid forward speed, about 21 mph, and is not expected to linger over Queensland after landfall. The heaviest rainfall will miss Queenland's most populated regions to the south that had the worst flooding problems earlier this month, including the Australia's third largest city, Brisbane.

Yasi will bring highly destructive winds to a region of coast south of the city of Cairns (population 150,000.) Townsville (population 200,000) is farther from the expected landfall of the eyewall, and should see lesser winds. Strong building codes have been in place in Queensland since the 1960s, which will help reduce the damage amounts. The fact that Yasi's eyewall will miss these two major cities is lucky, since the coast is less populous between the two cities.

A dangerous storm surge in excess of ten feet can be expected along the left front quadrant of the storm where it comes ashore. The tidal range between low and high tide along the coast near Cairns will be about 2 meters (6 feet) during the evening of February 2. Yasi is expected to hit near midnight, halfway between low and high tide. Thus, the inundation from the storm surge will be about 1 meter (3 feet) less than it would have been had the storm hit at high tide.

Yasi is larger and more dangerous than Cyclone Larry of 2006, which hit Queensland as a Category 4 storm with 135 mph winds. Larry killed one person and caused $872 million in damage (2011 U.S. dollars.) Yasi will bring heavy rains to a region with soils already saturated from record rains, and may become a billion-dollar cyclone.

Figure 2. Tropical Cyclone Yasi as captured by the Willis Island radar, as the western eyewall of Yasi moved over the island. Image credit: Australian Bureau of Meteorology, and kindly grabbed for me by Margie Kieper.

Links to follow:

Live streaming video from Channel 9 in Cairns, Australia

Jeff Masters

Winter Weather Hurricane

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.