Long Range Pattern Outlook #3

Brief Overview:

Tonight’s long range pattern outlook focuses on the first half of November, regarding the medium range pattern and the warmer pattern developing, along with the November outlook. The final winter outlook will be posted towards late November.

 

 

 

 


Pattern Outlook Archive

<< Pattern Outlook #2 – October 16, 2012
Pattern Outlook #3 – November 4, 2012
>> Pattern Outlook #4 – November 11, 2012

 


“Long Range Pattern Outlooks” are short discussions focusing on the pattern near and beyond the seven day range, regarding where temperatures and precipitation may end up compared to average, occasionally including hints of the longer range beyond the 2-3 week range. Pattern outlooks are usually issued weekly, unless a significant weather event happens in which case they may be delayed or cancelled for that week.

 


Expected Pattern Teleconnections:

  • NAO – positive; becoming neutral mid month

  • AO – positive; becoming neutral mid month

  • PNA– negative

  • EPO – negative; becoming neutral mid month

Medium-Long Range Outlook:

Following hurricane Sandy, the highly anomalous block south of Greenland fell apart, although ridging continued near Greenland over the last few days. The Northeast US region remains in a colder then average pattern which started with Sandy and will last through late this week, when a nor’easter affects the region – more information on this will be posted with a special update on Monday afternoon. Behind the nor’easter, however, changes in the pattern will take place which will last through the middle of the month and potentially towards the end as well.

The PNA (Pacific / North American Pattern) is currently positive, which supports ridging in the western US, but will turn strongly negative as ridging shifts into Alaska and a strong trough drops into the western US. Meanwhile, the NAO will rise to slightly positive with lower heights returning into Greenland, which along with the -PNA will support a strong ridge developing over the eastern half of the US, as the GEFS 500mb anomaly map from the PSU e-Wall shows to the left. The ridge building in from 11/10 to 11/13 will result in warmer temperatures affecting the region, with widespread highs in the 50s expected and the potential for a day or two of 60+ degrees in the NYC area.

A developing low pressure will move through the Great Lakes region into Canada with a cold front approaching the region around the 13th, but with a continued negative PNA and slightly positive NAO, is not expected to bring any strong cool down to the East, with a ridge likely rebuilding behind the storm. Overall, the pattern through somewhere around 11/18, possibly earlier or later, is expected to end up warmer than average for the East, with near to below average temperatures in the western US, western Canada and southern Alaska. This time period will start out drier than average, mostly due to the strong ridge in place, but may trend wetter towards the end. Towards the end of this time period, however, the NAO slightly drops while the PNA rises back towards neutral; there is more uncertainty towards the 11/18 time frame but while at this time, it does not appear that a strong pattern develops afterwards, the warm pattern for the middle of the month is likely to moderate by then.

Regarding the November outlook, while the first week of the month is colder than average, the middle of the month will be warmer than average, perhaps much warmer on a few occasions. While the end of the month will determine the final outcome of the month, the possibility is there that parts of the area end up with their 20th consecutive warmer than average month, even if only slightly warmer than average, with precipitation potentially slightly wetter than average. More information on the November temperature outlook will be posted with the next long range pattern outlook.


Pattern Outlook Verifications

Verifications of each pattern outlook are posted 3 outlooks afterwards; for the 1st outlook, the verification will be posted with Pattern Outlook #4.

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