Friday, April 6, 2012

Time to really get into this weather stuff

Today is April 6th! And we are getting dangerously close to the magical window of late April migrants and vagrants.... Time to play around with the weather forecasts:


*Disclaimer -- I don't really know my weather stuff that well, so who knows how correct/accurate any of this is.. But I enjoy it, and it's my blog.. so yeah.....

---- So all winter long we had warm weather... Nearly constant S/SW/W winds (virtually no N to NE winds) and above normal temperatures. My understanding is that an extremely positive "North Atlantic Oscillation" (or NAO)  was to blame.  In short, it's the connection/interaction between a powerful LOW pressure system near southern Greenland and strong HIGH pressure over the subtropical atlantic (Bermuda/azores high?)

When the NAO is "positive" it means that each of these centres of pressure (low and high) are very strong and feeding off each other. In order to feed this strong "system", it literately sucked warm air from the southern USA (across southern Ontario) and out over the ocean to feed the cycle of the NAO.

Here's a fun map (detailing winter) for this pattern:

Over the past ~10 days, we've had a dramatic shift in our weather patterns, with 3 of 4 days giving us the previously un-seen EAST to NORTH winds... Even this upcoming week has multiple days of N to E winds, that we barely saw all winter long. 

So that would lead us to believe that the NAO has changed a bit? Maybe? Here's the recent tracking:

Note hwo for the first time, it has dipped well into the negative (which it has hardly done for months!) Maybe a good sign why our weather patterns here have changed as well. 

But here's the fun part. The red line (on the top graph) is the various forecast models to predict what is going to happen next, and almost all of them shoot back into the positive by mid April. Which hopefully means higher temps + strong S/SW winds as we gear into top vagrant season! 


* this would be a good time to add another disclaimer, that the NAO is one of a dozen + factors that can affect our weather, so even if it looks good, there are several other things that can change how things play out..

A good example would be one of the most popular global weather "events/patterns" that can affect weather everywhere:  the El Niño/La Niña-Southern Oscillation, or ENSO

We've been in what was generally a multi-year La Nina event, (sea surface temperatures / SST being NEGATIVE in the tropical pacific ocean). Which generally means more storms in our neck of the wood, but things have been dying down (which I guess it is quite common for La Nina's to end in the March-May time frame). 

But in my limited experience, a waining La Nina event usually kicks out a few pretty good storms across the southern USA and into Ontario before it dies out... 

So my really rough and uneducated guess is that we have pretty good odds (50-75% chance) of a "good" early spring where we can get a solid wave of migrants/vagrants in late April, which has been more common than not in the last 10 years. 

Eg,/ like last year when late April was spectacular (also 2008)  compared to 2007 where things were slow until May 4-5..... But at the very least, we will have to wait and see! 

Current ENSO forecast: 

Note that most models are leaning towards positive SST's for the summer and fall, which is really bad for Cape Verde type Hurricanes (Fran/Isabel/Hazel that came into Ontario were all Cape Verde type storms, which means systems that originated in Africa) 

BUT.. let's not start thinking about Hurricanes until the spring is over!

1 comment:

  1. i'm predicting 6 species of warblers next weekend....