23 September 2011

Happy Equinox!

Posted by Dan Satterfield

The autumnal equinox was at 09:05 GMT this morning which is 4:05 AM USA Central Daylight time. I thought it would be fun to show the 18Z Meteosat image of the Earth from the Solstice on 21 June and compare it with today’s at the same moment.

June 21:


From Dundee Univ. Meteosat downlink. 18Z 21 June 2011

and today


18 Z 23 Sep. 2011. Notice the terminator is now vertical.

We meteorologists have another way of knowing it is fall. Just look at the sunset spikes on the NEXRAD radars across the country. As the sun sets each day the radio energy hits the spinning antennas on the radar sites and causes a spike to show up. On the equinox, the spike is exactly due east (west) of the radar site at sunrise (sunset). The animated GIF below is courtesy the Plymouth State NEXRAD archive.

Notice the spike pointing toward Wendover, Nevada at sunrise.