Nov. 12, 2000
'Hole-punch' clouds over Melbourne
Photos courtesy of National Weather Service, Melbourne. Photographers: Matt
Bragaw, Peter Blottman. (See story below)
Ice crystals and the influence of the jet stream helped produce this dramatic
scene on Thursday, Nov. 9 over the National Weather Service office in Melbourne.
Meteorologists call this formation "hole-punch" clouds.
Ice crystals, jet stream winds combine for rare display
By David Larimer
FLORIDA TODAY weather columnist
A unusual cloud formation appeared in skies over the Space Coast on Thursday
caused by ice crystals and enhanced by the jet stream.
There is no scientific term for the cloud display you see above. The National
Weather Service calls the formation "hole-punch" clouds because of the
oval-shaped opening.
The image was captured by meteorologists Matt Bragaw and Peter Blottman at
the weather service office in Melbourne on Thursday morning.
The display is rare but has occurred in Melbourne skies in years past. In
1993, the weather service's Dennis Decker photographed a similar display.
His dramatic photo was published in a national weather magazine.
Randy Lascody, a senior meteorologist at the weather service office, explained
the conditions that led to the striking formation:
"The atmosphere on Thursday was very dry from about 5000 to 28,000 feet.
There was a rather extensive deck of cirrocumulus (mixture of 'super cooled'
water droplets and ice crystals) invading the sky associated with strong
westerly jet stream winds.
"However, the 'hole-punch' features were aligned north/south. This suggests
that there was some sort of 'wave' in the atmosphere that was causing
rising/sinking air couplets.
"This would cause ice crystals in the descending portion of the wave to fall
into the super cooled (liquid) cloud layer. When this occurs, the ice crystals
grow (at the expense of the liquid droplets). Therefore, a hole opened in
the deck of cirrocumulus.
"This process is similar to the principle used in cloud seeding to make cloud
particles larger and produce precipitation. In this case, the precipitation
aloft (meteorological term is 'virga') descended into the dry air below 28,000
feet and evaporated (actually, the proper term for this process is 'sublimated').
"The virga is evident in a few of the pictures descending from the center
of the hole in the clouds. This resulted in a cone-shaped cloud high in the
atmosphere that I'm sure a few people thought was a funnel cloud."
