WSI: Talking about the weather

December 22, 2010

Nothing meets the description of “a mixed bag” better than a winter aviation weather forecast. Icing, turbulence, strong winds, and wind shear associated with the more southerly, lower seasonal location of the jet stream in the atmosphere all can influence in-flight conditions or the essential go/no-go decision.

Clear, calm winter days demand just as much care. Bitter temperatures—and sometimes, extremely high atmospheric pressure—present their own unique seasonal challenges to pilot and aircraft. Even the briefest session circuiting the traffic pattern should be considered carefully in the coldest temperatures to avoid thermal shock to an air-cooled engine. High barometric pressure requires care to avoid overboosting a normally aspirated engine—not something you fret about in the heat and humidity of August.

Businesses with high energy costs, transportation demands, or weather-related risk exposure do all they can to be ready for whatever weather whimsy winter wishes to waft their way. Pilots can do the same.

So, what’s the outlook for the winter of 2010-2011? Andover, Mass.-based Weather Services International (WSI) recently released a seasonal forecast that heralds a season with La Niña, which is characterized by unusually cold temperatures in the equatorial Pacific Ocean, exerting its influence, with varying implications for different regions of the country. WSI also sees evidence that a “fundamental climate shift in 2008” may usher in weather patterns similar to those of 40 to 60 years ago. The unusually cold December 2010 was seen confirming the trend.

WSI “expects the upcoming period (January-March) to average warmer than normal across the south-central states and most of the East. Below-normal temperatures are expected across most of the northern and western US, especially in the northern Rockies and north-central US,” it said in a Dec. 21 announcement that provided monthly, regional weather projections for the country.

Just as there are long-term forecasts and today’s actual conditions, pilots must prepare in order to keep their aircraft ready for winter flying generally, and today’s flight in particular.

Not sure where to start? AOPA’s Pilot Information Center has information on all aspects of winter flying. From winterizing your aircraft to cold weather operations, to icing hazards—it’s all there, backed up by articles on specific winter topics in the AOPA Pilot and Flight Training magazine archives. And since different seasons present their own types of hazards, a series of articles discusses safety issues pilots should review as the seasons change.

Whether your first job is to remove those aircraft wheel fairings (they tend to accumulate packed snow) or install a winterization kit once the temperature goes below the maximum recommended ambient temperature for using one, get going on those projects.

And if you’re not one of the lucky ones with a heated hangar at your aircraft’s disposal, allow time before your flying for an engine preheat on those cold mornings. (Then get going before its effects are wasted.)

Always be sure to remove any frost accumulations on wings and control surfaces. Any pilot who trained during cold weather or in a northern climate has heard that admonishment since the earliest dual-instruction flights. But for others who may be visiting a cold place for the first time in a long time, it’s a reminder worth hearing.

As for the first part of that long-range weather forecast, expect warmer-than-normal January temperatures in the northeast and southeast (except Florida) and the south-central region; colder-than-normal conditions in the other U.S. central and western regions, says WSI.

Planning way ahead? WSI’s 2011 hurricane forecast is available, too. And it looks like 2011 is going to be an active year on the U.S. mainland.

Dan Namowitz

Dan Namowitz | Aviation Writer

Dan Namowitz is an aviation writer and flight instructor. He has been a pilot since 1985 and an instructor since 1990.