Saturday, April 20, 2013

Spring Pulls A Vanishing Act; Returns for May

Spring continues to do its magic and will be pulling a vanishing act until the beginning of May.

Pictured above is the 500 millibar height anomalies from forecast Day 6 to Day 10. Cold colors show low pressure anomalies, while warm colors portray high pressure. In the forecast image above, we see strong low pressure building over the Arctic to allow for a strengthening polar vortex. As a result of this  strengthening, warm weather is typically favored. However, high pressure building south of Greenland and in the Northeast Pacific will coerce the low pressure further south and allow cold air to make itself available in all the areas shown in blue. Again, usually, warm air would be favored as the cold air would be kept up north in the presence of such strong low pressure over the Arctic. However, the angling of those two previously mentioned high pressure systems will let the polar vortex squeeze some of that unseasonably colder air further south.

The long range American ensembles show 500 millibar height anomalies over the next sixteen days from left to right, top to bottom. We can see the polar vortex pushing south towards the US/Canada border, but by the time May rolls around in the bottom row of forecast images, we see abundant high pressure across the nation. This abundant high pressure formation is what is supposed to happen with strong low pressure in the Arctic. It looks like the nation-wide high pressure formation in early May would be tempered in the East US just because of persistent high pressure stirring around Greenland, but cold air should not prevail like it will in the next couple of days.



Eric said...

Hey Andrew, I've enjoyed reading your posts over the last several weeks, and since its been getting quiet around here, thought you would like to see my new post with even more (if you can believe that) hurricane season connections, my official summer forecast & even a sneak peek into next winter. (link)

Anonymous said...

Question Andrew, I have been keeping a close eye on your 12z GFS snowfall forecasts for tomorrow and Tuesday's storm here in Colorado, and I am seeing actually both the 12z and the 18z getting more and more aggressive with snowfall amounts generally in the 12"-18" range for my area, if this is the case, what is the ECMWF indicating at this time? and if that model and the NAM are reaching similar conclusions, then is there some reason why the NWS hasn't even attempted to release any watches or warnings as of yet, is confidence not high enough yet on snow amounts?

Anonymous said...

what has happened here?
used to be daily updates
comments and opinions about everything going on
now updates are only a few and are days with none
comments sometimes dont even show up
hope things are ok