Dr Hathaway of NASA has revised his Cycle 24 sunspot forecast. He predicts a smoothed sunspot number maximum of about 60 in the Spring of next year. Cycle 24 will be the smallest in about 100 years. For the record, his forecast graphed is shown below:
He has revised his prediction method as follows:
Recent work [see Hathaway Solar Physics; 273, 221 (2011)] indicates that the equatorward drift of the sunspot latitudes as seen in the Butterfly Diagram follows a standard path for all cycles provided the dates are taken relative to a starting time determined by fitting the full cycle. Using data for the current sunspot cycle indicates a starting date of May of 2008. Fixing this date and then finding the cycle amplitude that best fits the sunspot number data yields the current (revised) prediction.
To read more of the NASA report click here.
A reminder, Hathaway uses the smoothed International Sunspot Numbers and not the NOAA count. The International Sunspot Number for historical reasons [to be compatible with Rudolf Wolf’s count for 1849 to 1865] is reported as 0.6 x the actual count, while the NOAA count is just the raw count [actually = 10 x number of groups + number of spots].
This has not been an easy road for Cycle 24 sunspot predictions. See the links below to get an idea how far Cycle 24 has been cut back over recent times.
The April Sunspot report will be out early next week and will be posted for your examination.