72° in New York City; Avalanche rips Colorado highway

The heat is on in New York City! The temperature soared to 72° at New York's Central Park Saturday, tying their all-time warmest January temperature ever. New York City has hit 70 degrees in January only twice before since record keeping began in 1869--on January 4, 1932 (70°), and on January 26, 1950 (72°). The 72° reading is a full 34° above their normal high of 38. Records were smashed all over the Northeast today. Philadelphia reached 73° and Newark hit 72°. The all time record for January warmth was 74 °in both cities, set on January 26, 1950. Hartford, Connecticut hit 72,° besting their warmest January temperature ever--70, °set on January 14, 1932. How unusual is this winter? La Guardia airport broke their all-time record for the date (59) °at 6am this morning, when the minimum temperature is usually measured! La Guardia went on to post their warmest January temperature ever, 72°. New York City has not seen a single flake of snow this winter, surpassing the winter of 1877-1878 for the longest stretch without snow (a trace of snow was finally measured on January 4, 1878 that winter). New York City averages 22.4 inches of snow per year. While the current weather forecast does show some colder air moving into New York and most of the U.S. over the next week, no snow is forecast for New York City for at least another week.

The reason for the warmth? A moderate El Nino event is adding a tremendous amount of heat to the globe this winter, and has helped displace the jet stream farther to the north than usual. Global warming is also partly to blame, along with natural variability in the Earth's weather. I also believe that the on-going melting of the Arctic Ice Cap may have contributed to this winter's warmth, although it is difficult to know how much so without doing detailed model studies. Record low levels of sea ice in the Arctic in November and December have exposed much larger areas of open water than usual. The open ocean water provides a tremendous source of heat to the atmosphere, and the extra moisture from the open ocean areas creates cloud cover that insulates the surface. This has allowed less cold Arctic air than usual to form over the Northern Hemisphere. However, now that we are well into the coldest part of winter, the Arctic sea ice has frozen up more. This, combined with the natural cooling due to the 24-hour darkness that continues over the pole, is allowing a large area of cold air to form over the pole. The latest runs of the GFS computer model show that this Arctic air will plunge southwards over North America during the next two weeks, bringing near-normal winter conditions to the U.S. and Canada during the second and third weeks of January. However, exceptionally warm conditions will continue over most of Europe and Asia during this period.

Colorado's tough winter continues: huge avalanche buries cars
Denver's third major snowstorm of the winter brought up to 8 inches of snow to the Denver area today. The heavy snow triggered a major avalanche 60 miles west of Denver that buried a 200-foot wide section of U.S. Highway 40 to a depth of 15 feet. Two cars plunged over the edge, but all eight people inside were rescued. The avalanche occurred near 11,307-foot-high Berthoud Pass. Colorado has had a lot snow, thanks to a kink in the jet stream that has put the predominant storm track over the state. However, the weather has not been very cold--the average temperature in Denver during December was 1.4° above normal, thanks to warm weather that moved into the region before and after each major storm. About 95% of the U.S. had above-normal temperatures in December.

2007 to be warmest year on record?
There is a 60% chance that 2007 will be the warmest year on record, according to a forecast issued by the United Kingdom Meteorological Office on January 4. The forecasters cited the combined influence of the continuing global warming trend, and the presence of a moderate El Nino event. "Even a moderate (El Nino) warming event is enough to push the global temperatures over the top," said Phil Jones, director of the Climatic Research unit at the University of East Anglia. The warmest years on record were 2005 and 1998, when the global average temperature was 1.2°F higher than the long-term average of 57°F. Given the remarkable warmth across not only North America this January, but also Europe and Asia, I think that a 40% chance of a warmest year ever is a reasonable forecast, but 60% might be too high. Not all El Nino events create a big increase in global temperatures.

I'll talk more about the amazing warmth of this winter on Tuesday afternoon, when the National Climatic Data Center releases their U.S. statistics for December of 2006.

Jeff Masters