Sea fog arrives at Misawa for its annual visit
MISAWA AIR BASE, Japan — Monday wasn’t a holiday at Misawa, but it almost was quiet enough to hear the sea fog roll in.
American and Japanese fighter aircraft and trainers remained on terra firma because a thick layer of sea fog kept ceilings at or below minimums needed for safe flying operations.
“Today was a perfect situation for sea fog,” said Air Force weather forecaster Staff Sgt. Brian Bishop, “a strong easterly wind flow off the ocean that brought a thick layer of stratus overhead.”
As certain as death and taxes, an annual sea fog invasion begins in Misawa in late May and extends into August.
Japanese residents refer to the marine sea fog as yamase, or east wind, according to a Japan Meteorological Agency forecaster.
“This year it may have started somewhat earlier than usual,” said Capt. Steve Barlow, commander of the 35th Operational Support Squadron weather flight.
Whenever it arrives, it plays havoc with military flight training schedules. Air Force flight planners here say between summer sea fog and persistent winter snow showers, 22 percent of Misawa training missions, on average, are scrubbed.
That compares to an average rate of 8 percent to 10 percent at other Pacific Air Forces bases.
Bishop said several factors are needed to produce the sea fog, which at its peak — from late June to early July — can extend hundreds of miles off northern Japan’s eastern flank. “I’ve seen it extend pretty close to the Aleutians in Alaska,” he said.
Warm moist air moving over cold Pacific ocean waters east of Misawa causes a fog-forming condition meteorologists call advection.
A boundary of warm air builds to the south of Misawa; an easterly wind, from a high-pressure ridge parked north of Misawa, propels the sea fog onto land.
Bishop said the warm air south of Misawa is behind the “Baiu,” the seasonal rain front that already has triggered Okinawa’s rainy season.
The front migrates north. Usually, it passes the Korean peninsula by July and, shortly thereafter, Misawa, signaling the annual rainy season’s end.
Experienced Air Force F-16 pilots operating here usually have to scrub flight operations when ceilings over Misawa’s runway fall to 200 feet with half-mile visibility. Those with less experience don’t fly when lower than 301-foot ceilings and one-mile visibilities are present, said Lt. Col. Scott Dennis, commander, 14th Fighter Squadron at Misawa.
Commercial aircraft such as Japan Airlines and the American Trans Air Patriot Express landing at Misawa have precision radar systems that usually let them operate in thick fog.
Sea currents also affect the fog bank’s formation.
Bishop said the cold-water Oyashio current — which flows southward from the Sea of Okhotsk and Kuril Islands to off eastern Honshu — determines the fog layer’s depth. The warmer Kushiro current also influences fog bank development.
Occasionally, a low-pressure system will move through the area, providing a respite from the sea fog. But if winds return to an easterly orientation, the foggy conditions will generally return.
Usually by August, sea surface temperatures rise into the low 60s, eliminating the fog threat.
Despite forecasting aids such as satellites, weather balloons and reports from Japanese Air Self-Defense Force weather missions, forecasting sea fog is far from an exact science.
“Computer modeling does not take into account fog formation,” Barlow said. “We really don’t have a lot of tools to predict it.”
But later this month, forecasters here should have some extra help.
Barlow said following an agreement between Japan and the United States, a GOES 9 weather satellite will be “parked” over the Western Pacific for the first time, replacing an ailing Japanese satellite.
“It’s already in place and being tested now,” he said.