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Updates and Changes to the October Long Term Forecast

4 Oct 2017, 2:19 pm

Earlier this week, the Climate Prediction Center (CPC) updated it’s 30 day forecast for October and made several changes from the outlook issued last month. Temperatures over most of the west are now predicted to be below average. The previous forecast issued two weeks ago had most of the west seeing warmer than normal weather. Parts of the Southwest are still expected to see above average temperatures. The Northeast is still expected to see warmer than normal weather, with even higher probabilities forecast of that occurring. The Tennessee Valley is now expected to see a warmer than average month as well, with the previous forecast calling for below normal temperatures.

Significant changes were also made to the precipitation forecast. An area of wetter than normal weather has been shifted from the Northwest to the Upper Midwest and High Plains. Drier than normal conditions are now in the forecast from the Middle Atlantic into the Tennessee Valley, shifting out of the Central Plains. Florida is still expected to see above average precipitation this month.

The CPC states that the October outlook ” required substantial changes from the preliminary outlook. This is not surprising given that this time of year tends to observe some of the highest variability, large uncertainty and so often the lowest predictability during any time of the year.” The CPC expects that the first half of the month will see an upper level pattern with a period of robust troughs and storm systems across the west, with high pressure ridging in the Central and East. Later in the month, there are signs that the pattern may shift, or retrograde. This would focus the trough closer to the West Coast, with ridging in the Central sections of the nation. This accounts for the shift in precipitation forecasts and the change in the temperature forecast for the West.

The forecast was based on error correction (with the pattern shift), forecast model guidance, and long term trends. Even with NOAA issuing a La Nina watch recently, it will not be a factor here this quickly in October with development likely to be slow.

For WeatherNation: Meteorologist Mace Michaels

 

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