DISCUSSION: For most of the day on May 28, a dreary sky hung over southern New Jersey as a result of winds from the east off of the chilly Atlantic Ocean. As I looked out the window during the evening, I was shocked to see that the monotonous gray sky had been taken over by billowing, wavy features on the bottom of the clouds. These were none other than the breathtaking Undulatus clouds, which were formally recognized as a cloud type by the World Meteorological Organization back in March.
To be more precise, these are Undulatus Asperatus clouds, whose defining features include the wavy motions at the cloud base. The ingredients needed for these clouds to occur are rising air (to help with the formation of overcast skies) and some type of wind shear or turbulence. A developing area of weak low pressure offshore of Virginia Beach at that time may have provided enough of the required rising air motion.
Looking at a sounding would help us check for the second ingredient, wind shear. The sounding below (courtesy of the College of DuPage), is from the initialization of the 00z May 29 GFS model run for Atlantic City, where the cloud picture and video was taken. While the winds change direction with height - from east-southeasterly at the surface to southerly at 850mb - something else caught my eye. The winds actually slow down quite a bit as you move from the surface up to 700mb, where the white circle on the right-hand side indicates that winds were stationary.
Typically, winds increase with height as the force of friction from the ground becomes less apparent. The decrease of the winds with height in this unusual situation may have provided the kind of wind shear necessary for the Undulatus Asperatus to form.
Although the picture and video may look fascinating, trust me when I say that it was much more stunning to be there in person. I truly hope you all have a chance to view these clouds one day!
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© 2017 Meteorologist Jake Spivey