Lala Approaching Hawaii; Flash Flooding Risks; Excessive Heat

Lala, may become a hurricane, is expected to impact Hawaii this weekend. Heavy rainfall, strong winds, dangerous surf and localized flooding are expected. Heavy rainfall and flash flooding concerns from the mid-Mississippi Valley, Ohio Valley into the central Appalachians continues, with the threat shifting toward the mid-Atlantic later this weekend. Record heat continues for areas of the South. Read More >

Fallstreaks

What are they?

A fallstreak hole (also known as a "hole punch cloud") is a large circular or elliptical gap that can appear in cirrocumulus or altocumulus clouds.

How do 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. Planes passing through the cloud layer can bring these ice crystals.

Once the ice crystals are introduced, the water droplet quickly freeze, grow and start to fall. A hole is left behind, which will start to expand outward as neighboring droplets start to freeze.

The images below are from fallstreaks that developed on November 1, 2014 - contributed through facebook and twitter.


Houston, MN - Jamie Vix	Houston, MN - Lisa Shultz	La Crosse, WI - Maddie Schlittler	Minnesota City, MN - Tricia Duren

Rochester, MN - Grant Sherwin	Winona, MN - Jay Burros	Winona, MN - Jay Burros	...

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Lala Approaching Hawaii; Flash Flooding Risks; Excessive Heat

Fallstreak - What Are They?