Friday, 4 January 2013

Winter Is Coming Mid Month

In the Equatorial Pacific we can see the upwelling of colder then normal SST anomalies from 140w to 90w.
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This has contributed to the cooling of nino regions 3, 2 and 1. Further west the recent kelvin wave and WWB has caused subsurface warming in the western nino regions. Intensification of the WWB near 120w has worked to upwell warmth along the thermocline.
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We will see another spike in SST anomalies in nino 3 and 4 as the warming reaches the surface further east and MJO propagates into the western pacific around the 15th. This should help to enhance -OLR anomalies causing further warming in nino 4. The west/central based warmth along with the SOI drops should allow for significant cooling across eastern and central north america in late january and february. A tropical cyclone NE of New Zealand is contributing to pressure drops near tahiti but as it moves out a strong HP anomaly should move into the area. MJO propagation across the Eastern IO/maritime continent will allow for further SOI rises in the short range as low pressure anomalies continue across southeast asia. This signals a relaxation in the subsurface warming/SOI drops for the short term but as the EAMT gets going we should see these LP anomalies attempt to move eastwards in line with the MJO wave around mid month.
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The ECMENS are coming more in line with the GEFS pointing to an east based -NAO, -EPO and neutral to -PNA developing past the 15th which forces the core of the cold into the rockies/northern plains with storminess across the st lawrence valley, interior northeast and ohio valley. A strong SE ridge keeps the east coast above normal in this time period. Past 300 hours the GEFS is pointing towards a shift west in the blocking which allows the cold to propagate east and sets up the east coast for more storminess. Take the GEFS FWIW at this range but this is possible as the effects of the SSW slowly beat down the SE ridge from the 20th onwards. The brunt of the cold and snowfall should stay north of 1-95 with this setup overall. We are seeing conflicting signals between the unfavourable MJO, SOI drops, SSW and central based ENSO warming but i expect the cold to win out in much of the east by the 20th as the MJO losses amplitude and other cold signals win out. 

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