PMO Corner: Fall Streaks Over Miami

David Dellinger
Port Meteorological Officer - South Florida
NOAA/NWSFO, Miami Florida

Fallstreaks

Two “Fallstreaks” as seen from Port Everglades-Fort Lauderdale, FL.


On December 12th, 2014, Florida National Weather Service Forecast Offices, Television Meteorologists and local Law Enforcement Officials fielded calls and posts to social media sites from concerned citizens about strange and unusual cloud formations appearing from the Florida Keys to Central Florida. The cloud formations, called “Fallstreaks” started appearing in the morning and continued throughout the day.

What is a Fallstreak?

La Crosse, WI. National Weather Service Forecast Office Web Site defines it as: a hole (also known as a “hole punch cloud") or a large circular or elliptical gap that can appear in cirrocumulus or altocumulus clouds.

Fallstreaks Zoom

Enlargement of the above photgraph.


How They Form

High to mid-level clouds, such as altocumulus, are often composed of tiny water droplets that are much colder than freezing, but have yet to freeze. These "supercooled" water droplets need a "reason" to freeze, which usually comes in the form of ice crystals. Aircraft passing through the cloud layer can carry these ice crystals. Once the ice crystals are introduced, the water droplets quickly freeze, grow and start to fall. A hole is left behind, which will start to expand outward as neighboring droplets start to freeze. Navigate to the La Crosse WFO’s web site link to see more pictures of Fallstreaks: http://www.weather.gov/arx/why_fallstreaks.

Fallstreaks Zoom

As seen by satellite forming across Florida on December 12th, 2014.


The event in Florida is fairly rare as these environmental conditions are better suited for high latitude locations. The Fallstreaks over Florida were most certainly caused by aircraft descending through the cloud layer, on approach to local airports. The entire cloud formation continued to move eastward as the day progressed. Because of the rarity of the phenomena and the odd shapes these Punch Holes make when they form, they are often mistaken or attributed to unidentified flying objects or worse. However, rest assured; this is just another cool trick of nature.

Back to top