As the name suggests, these are well, mammary-like formations or 'pouch' like formations that typically form underneath the towering tops of thunderstorms.
While we've been socked in by fairly tame stratus (fog) clouds around the Bay Area, powerful thunderstorms nearby are making for some amazing sights.
Case in point -- this photo sent in by our NBC Bay Area Traffic Anchor Mike Inouye. In addition to tracking traffic, what I like about Mike is that he's also a part-time stormchaser for us.
Check out this snapshot he sent in from just east of Nyack on Saturday evening. The gallery below will take a closer look at what's known in meteorology as "mammatus" clouds. As the name suggests, these are well, mammary-like formations or 'pouch' like formations that typically form underneath the towering tops of thunderstorms.
How these formations are created is still up for debate. The common theory is that areas of ice crystals (denser, saturated air) begin to sink (negative buoyancy) then form smaller, eddy-like features that appear as circular cloud formations. As the air continues to descend and drops below the 100 percent relative humidity threshold or become unsaturated, the cloud basically 'stops' or forms the boundary line between the cloud shape and the surrounding dry air.
These features are not always indicative of severe weather and can form in a variety of weather environments. But as seen here in Nyack, this was part of a decaying thunderstorm near sunset. Often you'll see towering thunderstorms triggered by intense daytime heating and mid-level moisture streaming in from the south over the crest of the Sierra. Nickel and quarter-size hail was reported at times from some of these thunderstorms -- if the latter is true, that's nearing the threshold for severe thunderstorms.
Around the time of Mike's photo, as the sun begins to set, these storms will lose the benefit of daytime heating and usually weaken rather rapidly after sunset. It's a reminder that sometimes you don't have to head out to the Great Plains to get a taste of some powerful thunderstorms this time of year or see some clouds with names that make folks giggle.
Rob Mayeda still has issues saying "mammatus" clouds on air.