Waterspout and Rainbow Odd Couple

December 16, 2011

BowandspoutIMG_5370 (3)

Photographer: Geert Sassen; Geert's Facebook page 
Summary Author: Geert Sassen; Jim Foster

December 2011 Earth Science Picture of the Day Viewer's Choice This "odd couple" photo was captured in the eastern Mediterranean Sea on November 24, 2011 at about 4:00 p.m. The weather at the time of the photo seemed quite benign; calm seas, rather light westerly winds, fairly high barometric pressure (30.03 in or 1017.3 mb), air temperature of 78 F (25.5 C). I was aboard the Dutch container vessel, Maersk Kalmar, of which I'm captain, and was surprised to see a rainbow and waterspout in such close proximity to one another. I estimated the spout to be approximately 1,000 ft (304 m) from my position.

We're accustomed to seeing rainbows when the weather is improving -- when storms depart. This is because in the zone of the westerlies, following an afternoon storm or rain shower, the Sun is in the west and a rainbow, if visible, stretches across the eastern sky. However, as long as the Sun is shining, there are raindrops falling in the antisolar direction, and the Sun is lower than half way up the sky (no more than 43 degrees above the horizon), it's possible to see rainbows. This is so regardless of the season, the compass direction or whether or not a tornado or waterspout is in the vicinity. Waterspouts generally occur in the tropics or in the lower mid-latitudes during the warmest months of the year. As with a tornado, a rotating column of air dangles from a cumiloform parent cloud, but waterspouts, like the one pictured above (south of Crete, Greece), are neither associated with severe weather nor thunderstorms. Nonetheless, they can cause damage to small boats but most often dissipate when arriving onshore. I actually witnessed three different waterspouts this afternoon -- the one shown above being the most noteworthy.

Note that the camber of this particular waterspout coincidentally matches that of the right-most portion of the rainbow. However, whereas a pot of gold lies at the end of the bow, the stirred up water where the spout touches down gives up but a fine kettle of fish

Photo details: Camera Maker: Canon; Camera Model: Canon PowerShot SX30 IS; Focal Length: 18.595mm;
Aperture: f/4.5; Exposure Time: 0.0031 s (1/320); ISO equiv: 80; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB.