Posted: Sep 10, 2020 / 03:26 PM EDTUpdated: Sep 10, 2020 / 03:26 PM EDT
This is a map showing sea-surface temperature anomaly – or difference from average. A large portion of the world’s oceans currently have warmer than average surface water temperatures. The exception is along the equator west of South America. This pattern of colder than average water along the Equatorial Pacific is called “La Nina”.
When the winds are generally stronger along the equatorial Pacific, they stir up colder water from below the surface. Winds here in ithe Great Lakes are variable, but the prevailing wind direction is from the west. In the tropics, the prevailing wind direction is from the east.
This map shows a common prevailing pattern for during La Nina. With the exceptioin of fall hurricanes, the South is often a little drier than average, while it’s on the wet side in the Ohio Valley and Pacific Northwest. Cold air moves from Alaska and N. Canada into the Northern Rockies and Northern High Plains. This week we have seen a significant cold shot move down from Canada, all the way to Texas. It’s brought record cold and snow to Colorado and Wyoming.
This map shows where there was at least a little bit of snow on the ground this morning. Alamosa, Colorado had a 6″ snowcover. It’s strange to see snow on the ground as far south as northern New Mexico, while much of northern Canada is snow-free.
It’s still a little early to come up with a winter forecast. We often wait to see where early snowcover appears in Siberia and N. Canada. Last winter we had very little lake-effect snowfall in S. Lower Michigan…with about an average amount of “synoptic” snow caused by passing low pressure centers and fronts. Flint had more snowfall last winter than Muskegon – that’s pretty much unheard of. We had a sunny and warm summer, but that’s not an indication of what this winter will bring.