Watch: Towering cumulus cloud mimics Mt. Rainier in creating own hat

    Towering cumulus cloud makes its own lenticualr cloud over Puget Sound (Photo courtesy: Greg Johnson,

    Seeing "hat clouds" -- or lenticular clouds atop Mt. Rainier or other local mountains is a fairly frequent occurrence around here.

    But have you ever seen those hat clouds form atop...another cloud?

    One particular towering cumulus cloud over Puget Sound had enough vertical structure to mimic a mountain top on Sunday, briefly making its own lenticular cloud, also known as a "Pileus" cloud.

    Watch from the's web camera in Hansville:

    And here it is at full speed:

    The clouds are formed when you have a steady flow with air near saturation. In Mt. Rainier's case, when the wind flows over the mountain peak, the subtle rise in altitude provides just enough cooling for that air to saturate into a visible cloud. As the air sinks down the other side of the peak, it slightly warms and dries, becoming invisible. The cloud appears to park over the peak, but it's actually air continuously flowing over the top.

    In Sunday's case, the updraft inside the building cumulus cloud created a "bump" in the horizontal air flow for this lenticular cloud process to occur. In Mt. Rainier's case, a lenticular cloud is a sign of rain within 24 hours but when a cumulus is the culprit, it will rain much sooner!

    News In Photos

      Loading ...