A Nation Divided: Heat and Cold Records Split the U.S.

By: Bob Henson , 5:50PM,GMT on February 20,2015

This winter’s persistent U.S. gap between western warmth and eastern cold grew into a chasm this week. While unseasonable, unsettling mildness continues to bathe much of the West, one of the strongest February cold outbreaks in U.S. weather history--perhaps the worst and most widespread for so late in the winter--has taken hold from the Mississippi Valley eastward. Freezing temperatures pushed into parts of central Florida on Friday morning, with readings diving below the 0°F mark as far south as Tennessee. Cleveland, Washington, Baltimore, and Philadelphia all reported their coldest air since the 1990s. At least 500 daily record lows have been set or tied since Sunday, including several record lows for so late in the winter (including 9°F in Norfolk, VA, and –18°F in Lexington, KY, both on Friday) and a number of monthly lows. Crowning the list are the all-time record lows set or tied this week in four states:

Monday
Erie, PA: –18°F (tie], old record –18°F on Jan. 19, 1994; records began in 1873
Tuesday
Jamestown, NY (COOP station 4 miles ENE of town]: –31°F, old record –30°F on Feb. 17, 2015, and Feb. 12, 1979; records began in 1960
Friday
Lynchburg, VA: –11°F, old record –10°F on Jan. 21, 1985, and Feb. 5, 1996; records began in 1893
Flint, MI: –25°F [tie], old record –25°F on Jan. 18. 1976; records began in 1921

Gaylord, MI set an all-time lowest daily high at –5°F on Thursday, breaking the record of –4°F from January 27, 1986. Two unofficial lows of –39°F came in on Friday morning from automated reporting stations at Roscommon and Spincich Lake, Michigan.

Many cities in the Great Lakes and Northeast, and perhaps some entire states, are on target for the coldest February on record. Below is an update on three spots we examined in Monday’s blog post. With deep snow cover firmly in place, and the cold expected to persist through most if not all of next week, Bangor and Caribou should easily cruise to record-low monthly readings, while a brief warmup in Boston will likely kill its chances at a record-cold month.





Figure 1. A deep snowpack remained over New York and New England at 0600 GMT Friday, February 20, with lesser amounts prevailing from Missouri northeastward. Image credit: NWS/National Operational Hydrologic Remote Sensing Center.


A dangerous ice threat for the weekend
From the mid-South northward and eastward, extensive snow cover (Figure 1) is aiding and abetting the atmosphere’s plunge toward daily and monthly record lows. A new storm this weekend will bring a significant icing threat across a large area, with rich moisture surging atop very cold surface air that may be tougher than usual to flush out. Winter storm warnings are again in effect for parts of Arkansas, Tennessee, Alabama, and Georgia, with up to a half-inch of freezing rain possible in some areas Friday afternoon and evening before surface temperatures rise well above 32°F on Saturday. Precipitation will kick off as snow in many areas, including the East Coast from Washington to Boston, before transitioning to a wintry mix and eventually to rain, ahead of yet another Arctic blast early next week.

As the East shivers, the West simmers
While the eastern U.S. grapples with record cold, several Western cities are gunning for their warmest February on record, including those below. The last time Salt Lake City recorded a low temperature below the average for the date was on January 22.





Figure 2. Temperatures on Friday, February 20, are more than 30°F below average across much of the eastern United States, while above-average readings extend from western Mexico north to the Arctic coastline. Image credit: ClimateReanalyzer.org/University of Maine.


When have we seen this before?
The meridional jet-stream flow arcing north into Western Canada and dipping back south into the United States is striking in its persistence and strength, and there is a growing body of research into the effects of climate change and Arctic warming on jet-stream behavior. At the same time, there are some precedents for our current pattern, according to Weather Channel lead meteorologist Michael Palmer: “The highly amplified upper pattern with cross-polar flow that's been in place across North America this February is uncommon, but certainly not unprecedented. Some of the analogs that show up are February 1934, 1958, and 1963. In fact, much of that record cold from 1934 in the Northeast is being threatened with this current cold spell.” Showing how quickly things can change, the Dust Bowl year of 1934 went on to become the hottest year in U.S. weather history--a title it held until 1998.


Two severe tropical cyclones make landfall in Australia on the same day
Forecasters had their hands full at Australia’s Bureau of Meteorology early on Friday (Thursday US time), as Tropical Cyclones Lam and Marcia made landfall just six hours apart. Both systems intensified rapidly as they approached land.


Figure 3. The VIIRS scanning radiometer aboard a NASA satellite took this image of Marcia as it approached the coast at 1458 GMT Thursday, February 19. Image credit: NOAA/NASA RAMMB/CIRA.

Cyclone Lam made landfall about 500 km east of Darwin on Australia’s sparsely populated north-central coast around 1430 GMT Thursday (2:00 AM Friday local time). Several homes were reported destroyed in the town of Galiwinku, with water and power outages that could last up to a week. Marcia (Figure 4) struck a somewhat more populated area on the northeast coast near the small city of Yeppoon and Rockhampton at 2200 GMT Thursday (8:00 AM Friday local time), with power lines and trees down and some structural damage but no large-scale injuries reported. Satellite-estimated sustained winds at landfall were 105 mph for Lam and 125 mph for Marcia, with a gust to 129 mph reported at Middle Percy Island. Marcia is the strongest cyclone on record to strike the east coast of Australia so far south (around latitude 22°S). Cyclones heading for the Queensland coast, as Marcia did, often recurve at lower latitudes than hurricanes approaching the U.S. East Coast.


Figure 4. A visible satellite image shows the decaying Cyclone Lam (top center) and the intensifying Cyclone Marcia (right center) at 0033 GMT Thursday, February 19. Image credit: Japan Meteorological Agency.

According to climatologist Blair Trewin (Australian Bureau of Meteorology), this marks the first time since routine satellite coverage began in the 1970s that two severe tropical cyclones (sustained winds of at least 74 mph) made landfall in Australia within 24 hours of each other. In terms of geography and timing, it’s as if one hurricane hit Louisiana and another struck North Carolina later the same day. We can’t rule out same-day landfalls having happened in Australia prior to the 1970s, since the strength of many cyclones along the poorly sampled coast was likely underestimated in the pre-satellite era. Sea-surface temperatures were about 1-2°C above average in the regions where both Lam and Marcia developed. More details on the twin Aussie storms--referred to as a “cyclone sandwich” by locals, according to the Associated Press--can be found at the ABC live blogs on Lam and Marcia.



This week’s WunderPoster: Kelvin-Helmholtz Instability
The latest installment in our WunderPoster series (Figure 5, right) spotlights the graceful, symmetric clouds formed by Kelvin-Helmholtz instability. These shallow mid-level clouds can develop when a disturbance moves into two closely spaced layers of air that have strongly different densities and wind speeds, much like the interface between air and water that helps generate ocean waves. All WunderPosters can be downloaded in formats suitable for posters or postcards.

Bob Henson


Figure 6. Kelvin-Helmholtz instability produced these majestic clouds over Seattle, Washington. Image credit: wunderphotographer ChatNoirPhotographie.

Addendum: A Personal Cold Record for Dr. Jeff Masters
I’ve seen my share of cold temperatures, living in Michigan most of my life. But this morning, I set a personal record for coldest lifetime temperature when the mercury plunged to -29°F (-34°C) at my back yard Personal Weather Station in Highland, Michigan, 30 miles north of Ann Arbor. By six degrees, this is the coldest air this hardy northerner has experienced in his 54 years on the planet. I walked out to get the newspaper just after dawn, when it was -25°, to get the experience of the coldest air of my life. The air had a still clarity that the snow-reflected sun echoed brilliantly through. The cold made my nostrils feel all crinkly and tingly, and bit into my face with aching intensity. I tossed some water in the air to see if it would freeze before hitting the ground, but it wasn't cold enough for that. Now that I can say I’ve had the experience of -25° air, my California-based co-worker, Andria Stark, says that I should switch to the digital version of the newspaper in winter. But what fun is that? I like to always be aware of and connected to the atmosphere that surrounds us--though briefly in the case of -25° temperatures!

Have a great weekend, everyone!

Jeff Masters