Reading between the lines of the most recent long term (December through February) forecast by the National Weather Service (NWS), one meteorologist notes it “does not discourage a long term forecast of cold temperatures in the East.”

The recent revision to the NWS long term outlook predicts a weather pattern that will carry above normal temperatures over the Southwest, and the western central U.S. What that suggests to Scott Yuknis, meteorologist with Meteorlogix, Boston, is that it’s very likely that it would be colder than normal somewhere else — possibly in the East.

Yuknis suggests that the way to use the NWS forecasts is to look at the elements that they appear to have confidence in and use them to derive what will happen elsewhere. The latest forecast suggests there is “a pretty strong onshore Pacific flow, and probably some downsloping Chinook type warming patterns coming off the Continental Divide or also a ridging pattern.” If this pattern does indicate their thinking, then it indicates cold temperatures in the East. Yuknis said. “The trough has to be somewhere.”

The warmer than normal temps in the Southwest and western central U.S. “implies to me that cold weather is going to occur somewhere else, i.e. colder than the averages for a 90-day period. The chances are that the colder weather is going to favor the East.” Changes in the NWS forecast can be as important as the new data itself. In earlier forecasts the NWS had predicted a warmer scenario over the Southeast, but that trend is now absent and that’s an important development, Yuknis said.

“The precipitation forecast is also worth noting. The long term NWS forecast suggests that it will be wet over Texas, wet over Washington — that is new — and dry over California. What this means on average is strong onshore flow over the northern Pacific Northwest,” says Yuknis. That indicates that the jet stream will be slightly further north than what it typically is and this implies a persistent ridge pattern over the western part of the country. That also demonstrates a downhill trough in the middle of the country probably merging with a southern tropical jet stream which produces the moisture over Texas.

Under those conditions Florida is typically dry and also mild, and that’s what the NWS is showing. “You have to apply a weather pattern that makes sense with all of this,” he said. An important part of the interpretation of NWS forecasts and updates is determining what has been left out. “What hasn’t been said can be as important as what they do say.”

“They have indicated warmer temperatures in the West, but where is the offsetting cold? Even though NWS is not saying specifically that the East will be cold at this particular point in time. Keep in mind that this particular forecast by the NWS does not discourage a long term forecast of cold temperatures in the East.” He pointed out that the trend from previous forecasts is taking the warmth out of the East and returning to normal temperatures.

Although a cold forecast for the East may not be discouraged, it’s important to note that the persistent bone-chilling experience of last year is not what is being suggested. The main point is that the weather patterns this year are likely to be highly transitional.

The NWS forecast may be viewed at www.cpc.ncep.noaa.gov.

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