Aviano forecasts protect people, assets

  • Published
  • By Senior Airman Aaron Chandler
  • 21st OWS
Scattered skies were forecast throughout the morning, with a forecast high temperature of 93 F for June 29 at Aviano AB, Italy. Thunderstorms were expected mid-afternoon, typical summer weather for Aviano. However, the day would be a true test of Operational Weather Squadron and Weather Flight interaction.

The synoptic situation on this day was complicated. The three-hundred millibar flow was from the west southwest over northern Italy, with a shortwave trough approaching from the Gulf of Lyon, off the French southern coast. In the low levels, a weak dissipating frontal boundary lay just north of the Alps. Throughout the morning, significant diffluence developed at 300 millibars, with the shortwave rapidly approaching the Aviano area. A mesoscale low developed west of Aviano, near Milan which pumped an abundance of low level warm, humid air from the Adriatic Sea into the Aviano area.

As the day progressed, the 21st OWS at Sembach AB, Germany and the 31st Weather Flight at Aviano saw the possibility of severe weather development, and discussed the situation in-depth. Satellite data indicated a mesoscale convective complex developing in north central Italy. By noon, the consensus was that 50 knot winds and large hail were likely. The OWS issued a weather watch for hail greater than one-half inch and winds greater than 45 knots meeting severe criteria in U.S. Air Forces Europe. The flight initiated Severe Weather Action Procedures and notified the 31st Fighter Wing that the weather situation was deteriorating. The wing initiated Weather recall for all airborne F-16s, and postponed afternoon flights. The 1:00 p.m. TAF called for thunderstorms in the area after 2:00 p.m., with severe thunderstorms from 3 p.m. to 6 p.m.

As the storm passed Ghedi in north central Italy, winds reached 37 knots, with one-half inch, to three-quarter inch hail. After more discussion with the flight, the OWS issued a weather warning for 50 knots and one-half inch hail, valid at 3 p.m. Satellite imagery showed cloud top temperatures colder than -76 F, well above the tropopause. Radar images showed a well organized line of thunderstorms, with tops above 40,000 feet.

The storm's arrival at Aviano was spectacular. The onset was accompanied by an initial gust of 37 knots. However, a lightning strike caused a power outage on the airfield, knocking out all of the U.S. Air Force weather equipment. The peak gust occurred at 2:50 p.m., recorded by the Italian Air Force weather station, at 82 knots exceeding the highest wind ever recorded at Aviano by 24 knots. Small hail was recorded by the U.S. Air Force weather station, although an obvious hail shaft passed just north of the airfield.

The main storm passed quickly, moving northeast at 35 knots. However, it left a path of destruction in its wake. Nine people sustained injuries; although none were life-threatening, two required hospitalization. Most of the injuries occurred when the storm blew the roof off the Health and Wellness Center, trapping some people inside. On the flightline, a clamshell hangar was blown over, upending a UH-60 helicopter and breaking its tail boom. Around the base, significant damage was apparent. Scores of trees were uprooted, fences flattened, and roof tiles were missing from many facilities. Near the weather station, the Styrofoam insulation from the roof of the Precision Measurement Equipment Laboratory was completely stripped. Styrofoam blanketed the northeast corner of the base like snow. Cars were damaged from flying debris, and some were buried when a concrete carport collapsed onto them. Excluding the damage to the helicopter, financial damage from the storm totaled nearly $3.5 million.

While this storm was potentially devastating, close communication between the OWS and the flight is credited with the prevention of more significant injuries or loss of life. The 31st FW benefited from three hours lead time. Aircraft were recalled, flightline operations were suspended, and the base was prepared.

"A weather event of this type and the damage that resulted, should remind organizations at every base the importance in disseminating the potential danger of severe weather moving into the area to the lowest level," said Capt. Chad Little, commander of the 31st Operations Support Squadron's Weather Flight.

"Our weather flight did an outstanding job coordinating with local agencies and working together as a team," he added. "Every weather technician pitched in to help either disseminate weather warning information, answer questions over the phone, observe the constantly changing conditions, or mop up the water seeping through the doors; it was a total team effort."