June 27, 2013

Business aviation pilots face a wide range of weather hazards when flying internationally, but an NBAA webinar held on June 26 advises that understanding these phenomena before a flight – and their sometimes unexpected effects – can improve safety dramatically.

During the hour-long session, titled “International Weather Hazards and Impacts,” Jeppesen meteorologists Reuben Kast, Alison Fanara and Ray Stovall described challenges posed by monsoons, dust and sand storms, tropical cyclones and jet streams.

Monsoons, with their frequent thunderstorms and heavy rain, subject aviation to low ceilings, turbulence and reduced visibility. The South Asian or Southwest Monsoon affects India and Pakistan from June to September, while the East Asian or Southeast Monsoon affects China, Japan, Korea, the Philippines and Southeast Asia from May through August. The Indo-Australian Monsoon moves from Indonesia to Australia from September to February. The Inter-Tropical Convergence Zone (ITCZ), or Monsoon Trough, which can produce ice, moves between 10 degrees north in July to 10 degrees south in January.

Air France Flight 447, which crashed into the Atlantic Ocean en route from Brazil to Paris in 2009, might have benefited from a pre-flight weather briefing and a weather datalink, said Stovall, Jeppesen’s manager of meteorology. While the flight crossed an active ITCZ, many other aircraft were aware of the zone activity and diverted around it.

“Sometimes the ITCZ has very little activity and is not a problem, but sometimes it does have a lot of activity,” he said. “Be very aware of it.”

Dust and sand storms can damage aircraft engines and reduce visibility and are common in interior Australia, parts of the Middle East, the Gobi Desert in Mongolia and North China, and the Sahara Desert in North Africa.

Tropical cyclones form over tropical waters and generally move from east to west. When sustained winds reach 74 miles per hour, the storm becomes a hurricane or typhoon.

Clean-air turbulence is associated with jet streams, including the Polar Jet, which is strongest in the winter when it occasionally migrates to tropical latitudes and merges with the Subtropical Jet Stream. Pilots may also encounter the Subtropical Jet, which exists all year in the Southern Hemisphere and intermittently appears in the Northern Hemisphere in the summer; and the Tropical Easterly Jet, which appears over South Asia and North Africa in the summer.

For those who missed the live webinar, Members are encouraged to access the free archive copy of the recorded webinar online via the NBAA On Demand Education site.