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BLOCKING HIGH RETURNS... AGAIN
April 25, 2014 1:05 PM
Ah yes. That dreaded East, Northeast or Northerly wind for St. John's & the Northeast Coast. Unwelcome any time of year, but especially in the Spring months when the wind is rolling right in from the chilly waters of the North Atlantic. The onshore flow brings in that RDF: rain, drizzle, fog and cool temperatures, sometimes for days.
RDF for a day or two is tolerable. It toughens us up, puts hair on the chest and helps us to really appreciate those warm, sunny days of Summer, when there is no better place on earth. However when we get locked into these relentless 'blocking' patterns, when it's RDF on the menu day, after day, after day.... it chills us to the core, tests our sanity and makes many of us question why we choose to live on a rock in the middle of the North Atlantic. And it happens every year.
This current setup we are now diving head first into is no different than the examples above. The root cause is a blocking pattern or blocking high which is now setting up in the North Atlantic. We are now into what's called a negative phase of the NAO (North Atlantic Oscillation) which is basically higher than normal pressure to our North & Northeast.
The image above shows that the NAO has been in a neutral or positive phase (average to lower than average pressure in the North Atlantic) for most of the Winter, but is now tanking into a negative phase. The red lines are forecast model output which predict the negative phase to continue, before a trend back towards a neutral pattern late next week.
When these large areas of high pressure set up anywhere from Baffin Island, the Northern Labrador Sea to Greenland to Iceland, they essentially create a road block on the highway. That highway just happens to be the path that low pressure systems take as they leave our Province and head out towards Europe. With the highway blocked, the lows moving through our region have nowhere to go. They either slow down to a crawl as they move through, or in some cases, will actually sit and spin in our area for days. With high pressure firmly in place to our North & Low pressure to our South, NL most often sees East, Northeast or Northerly winds in these blocking patterns.
For those of us in Metro & the Northeast Coast we are once again heading into a long tunnel and it's dark, filled with rain, drizzle, fog and chilly temperatures. However, there is some hope. As of now, long range forecast models are showing some light way out at the end of this RDF tunnel, with the blocking pattern breaking down mid-late next week. Again, 'currently' it looks like we should see enough of a pattern shift to turn off the RDF machine and maybe even bring us some sunshine.
So yes, there is some light at the end of the tunnel, but until then, keep those Vitamin D pills handy. I'll keep you posted with your latest 7 day forecast, tonight on Here & Now.
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