Friday, 15 February 2013

Stormy Pattern Reverses By Mid March

The next 3-4 weeks will be pretty exciting for winter weather lovers across most of the nation. Blocking will be a key player with the MJO headed into unfavourable phases after the 20th of february. The wave will weaken as it propagates eastwards towards indonesia and the philippines which should keep the impacts much smaller. A less active SE ridge will hold until mid march.
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From Feb 20th-March 10th the mean trough will set up in the rockies with a strong blocking high across east hudson bay. Another key player will be the strong trough east of hawaii which will help enhance STJ disturbances. This will cause the mean storm track to set up across the ohio valley, interior northeast and great lakes with phasing possible if the timing is right. The recent SOI drop has definitely enhances STJ moisture which should make for an interesting few weeks as numerous storm systems move across the CONUS. Many storms will take a more southerly track with weakening as they move north into the eastern canada block.
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As we head into week two and three of march I do believe the SE ridge will begin to take over. Warmth will dominate the east as the stratosphere has cooled rapidly and the la nina continues to intensify. The IOD also looks to be transitioning into a negative state which will help contribute to mid latitude ridging. The GWO continues to stay in la nina phases with very negative MT anomalies and a northward momentum transport. This is responsible for the very active rossby wave train in the pacific and inevitable SE ridge strengthening that should occur in march. The GWO will head into 3/4 with strengthening IO convection.
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Currently we are seeing a CCKW propagating eastward in the central atlantic which may help amplify the MJO in a couple of weeks as convection increases in the IO region. The -NAO/ phases 1-2 of the GWO will keep the pattern very stormy over the next few weeks from the plains east. By mid march tropical forcing will cause the wintry pattern to break down especially if the MJO re-amplifies in the IO.
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