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Great Blizzard pounds Midwest; Australia braces for Category 4 Yasi

By: Dr. Jeff Masters, 2:37 PM GMT on February 01, 2011

The Great Blizzard of February 1 - 2, 2011 is here. Oklahoma City is experiencing whiteout conditions, with heavy snow of 2 inches per hour being driven by ferocious winds of 36 mph, gusting to 46 mph. With a temperature of just 9°F, this is an extremely dangerous storm for the city, and all of Oklahoma has been placed under a state of emergency. Seven inches of snow had fallen in Oklahoma City as of 7am EST. Dangerous blizzard conditions extend from Oklahoma, through northwest Arkansas, southeast Kansas, and southern Missouri this morning, and blizzard conditions are expected to spread northeastward into eastern Iowa, southern Wisconsin, most of Illinois, southern Michigan, northern Indians, and northwest Ohio later today. Cold air is being driven southwards out of Canada by a high pressure system over Montana that is at near-record strength. Pressures at Glasgow, Montana this morning were 1054 mb, close to the all-time U.S. high pressure record of 1064 mb set in Montana in 1983. Copious moisture is streaming northwards from the Gulf of Mexico to fuel the blizzard, and snowfall amounts will likely approach two feet across portions of Iowa and Illinois today, making it one of the top-ten snowstorms in history for the region. The storm will probably be Chicago's biggest blizzard since January 2 - 4 1999, when a storm dumped 21.6" of snow. With today'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.

Figure 1. Chicago's Calumet Expressway near 138th after the record blizzard of January 26 - 27, 1967. Image credit: NOAA Photo Library.

Many major cities will likely receive over 12 inches of snow from the Great Blizzard of February 2011, including Kansas City, St. Louis, Detroit, and Boston. Perhaps of greater concern is the potential for a major ice storm along a swath from Northwest Oklahoma to Massachusetts. Widespread freezing rain is expected to bring over 1/4" of ice to many major cities, including Indianapolis, Columbus, Cleveland, Pittsburgh, and New York City. Some regions could see up to an inch of ice, and widespread power outages due to toppled power lines are likely for millions of people. Damages exceeding $1 billions are possible from this ice storm. In addition, the storm's powerful cold front brought severe thunderstorms to eastern Texas this morning, and severe thunderstorms will affect Louisiana, Mississippi, and Alabama today as the cold front moves east. NOAA's Storm Prediction Center has placed the region under its "slight risk" threat area for severe weather today, and a few isolated tornadoes may develop this afternoon in some of the heaviest thunderstorms.

Figure 2. A world of white. I don't recall ever seeing such a large area of the U.S. covered by winter weather warnings.

Extremely dangerous Tropical Cyclone Yasi bears down on flooded 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 warm ocean waters of 29°C (84°C). The sea surface temperatures over the region of ocean Yasi is traversing (10S - 20S, 145E - 160E) were 1.2°C above average during December, the latest month we have data for from the UK Hadley Center. This is the highest value on record, going back to the early 1900s. Low wind shear and record warm sea surface temperatures will continue to affect Yasi for the next day, and the cyclone should be able to maintain Category 4 strength until landfall Wednesday evening (local time.)

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 NASA's Tropical Rainfall Measuring Mission (TRMM) satellite 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 near 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.

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 critical thing will be when Yasi hits relative to the tidal cycle. 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. If Yasi hits at low tide, a 10-foot storm surge will only bring the water levels four feet above mean tide, but a strike at high tide would bring water levels a full ten feet above mean tide. High tide is at 9pm EST (local) time in Cairns on February 2.

Yasi is comparable to 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 is a much larger storm than Larry, though, and will bring heavy rains to a region with soils already saturated from record rains. Yasi is likely to be a billion-dollar disaster for Australia.

Figure 3. Tropical Cyclone Yasi at midnight GMT on February 1, 2011. At the time, Yasi was a Category 3 storm with 115 mph winds. Image credit: NASA.

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.