Interesting Weather and Climate Information According to the climate records for 2014, Grand Rapids, MI did not reach 80F until May 8th, and did not reach 90F once all year. 1 or more days of each month had lows in the 40s, except for July. July had a few days with lows in the 50s, and in some cases, the low 50s. A lot of our cold air was thanks to a persistent positive phase of the PNA (Pacific-North American Pattern). A positive PNA typically has a large area of high pressure that gets stuck on the west coast of North America and in the eastern Pacific Ocean. This high creates a block. The low pressure systems ride up over the top of this block, usually crossing into Alaska, and northern Canada, before sliding down into the US from the NW. This creates a NW flow, and a NW flow is cold. Those lows drag down a lot of cold air with them sometimes, as we saw last winter especially. We had a positive PNA common throughout 2013 as well (another year that we spent a lot of time in the below average category in regards to temperatures in MI) In the satellite animation of the worlds weather, you can see storm systems repeatedly hitting what looks like an invisible barrier off the west coast of North America. That is the blocking high pressure. Of course, this is only part of the story, but a positive PNA has been a main driver of why our weather continues to be so cold in MI. Heres a link to the PNA trends which show trends from a few months past, current trends, and the future forecast trends. You can see how common the positive phase has been: cpc.ncep.noaa.gov/products/precip/CWlink/pna/pna.sprd2.gif Because of this positive PNA, the west has continued to suffer from horrible drought. A negative PNA would allow low pressure systems to bring rain to the west, and a negative PNA is what were in now, temporarily. The GFS is showing some relief for you folks in southern CA on Dec 2 climate.cod.edu/data/forecast/GFS/12/SW/gfsSW_prec_prec_102.gif Looking like a positive PNA will take hold again though in December. Unfortunately for you folks in the west. Enjoy the rain for a couple of days, it looks like thats about all youre going to get before the PNA goes positive again. In lower MI, enjoy the not so horrible temps this weekend, into early December. Stay Warm! - Charles Russell *Disclaimer: I am not a meteorologist, but Ive studied weather for many years, and from time to time, I like to share information, and my observations, with the rest of the world.
Posted on: Fri, 28 Nov 2014 22:16:42 +0000