CFSv2 Seasonal SSTs (clim19912020)
first  rec: avg(lastbs-1, lastobs, CFSv2 month 1)
second rec: avg(lastbs, cfs month 1, CFSv2 month 2)
last   rec: CFSv2 month 9
other  rec: CFSv2 3-mo average
 TrgSeason    SST34
   202403     1.14
   202404     0.58
   202405    -0.08
   202406    -0.63
   202407    -1.08
   202408    -1.42
   202409    -1.72
   202410    -1.94
   202411    -2.05
   202412    -2.06