Sunday, September 23, 2012

Special Long Range Lookout: Sustained Cold In Long Range

This is a special edition of 'Long Range Lookout', being presented after the 12z GFS brings unseasonably cold air to much of the north and west parts of the nation.

As seen above, the 11-15 day average for 850mb temperature anomalies is very cold- as low as 14 degrees below normal. This actually puts the 850mb temperatures cold enough to produce snow- an occurrence being shown by the same 12z GFS.

As is to be expected, the long range verifies a very small part of the time, so one would usually take this with a grain of salt. However, looking at past trends of the last few runs of the GFS focused on 11-15 day 850mb temp anomalies, the model has been steadily trending colder with each run. What I would take away from this is that an enhanced appearance of cold weather is likely in the next couple of weeks, but the intensity is unknown.

Also of interest is the 11-15 day 500mb height anomalies. Notice the strong signs of a positive PNA, with a strong ridge in eastern Alaska and western Canada. However, the lack of a ridge near Greenland will result in an obstacle of being able to get the cold air east.

Considering there is a strong disturbance anomaly over south central Canada and central Canada, there should be at least one storm system that sweeps cold air east and into the Midwest and Mississippi Valley. The west-to-east motion of systems in the North Hemisphere means that this cold air will eventually move east into the eastern US, but the intensity of that cold air is in question.


BREAKING NEWS: TS Nadine Regenerates

Tropical Storm Nadine has regenerated in the far northeast Atlantic this morning.

TS Nadine is now what I like to refer to as a zombie tropical cyclone, as it has come back from the dead. However, this system won't be eating anyone's brains, whether in the US or Europe. Nadine is expected to move generally west, with wobbles north and south while on that path.

Nadine should not pose a threat to land in the next several days, but in the future, the Azores may want to keep an eye on the system should it make a wobble north and send some moisture that way.


Minnesota Low Temps Typical of October

Observed low temperatures from last night and tonight's forecasted lows are actually typical of October in Minnesota.

Statistics show that the average low temperature in September is 46.6 degrees (F) for the state of Minnesota. However, yesterday's actual lows provided by show that some locations reached as low as 29 degrees in the far northern part of the state. This beats the average low temperature of 35 degrees (F) in October across the state.

So? Why should you care? In weather, many times forecasters can use the persistence method of forecasting to their advantage. For example, if it was unusually warm for a couple of days, a forecaster may use the persistence method and say that it will remain warm. If it has been very rainy the last several hours and the skies look dark, the forecaster may say it will continue raining.

If we use the persistence method here, averaged out over a long period of time, it is possible that this indicates that the Northern US may be cooler than normal for the rest of fall. Now, this method has a lot of caveats and is not really used now that we have computer models. However, the possibility is there that this is an indication from Mother Nature on what is to come as far as the rest of Fall goes.


Summarizing Recent Winter-Related Posts

I know what I have been putting out in the last several days has been confusing, because there's so much information and there isn't really any good way to put it out there without some confusion coming along. So, this post is dedicated to clearing up any confusion related to any of the posts I've been putting out in the last week or two.

Q: What's with the El nino?
A: The El Nino is present in the waters, meaning the waters are warmer than normal. However, the atmosphere is failing to recognize that there is an El Nino- lower level winds are not favorable for El Nino conditions.

Q: I heard of an underwater cold pool a few days ago. What is that?
A: There is a large expanse of cooler than normal waters that developed under the El Nino- about 100-200 meters below the surface. This cold pool of water could take away the warmth of the El Nino, possibly killing it altogether.

Q: So is there going to be an El Nino for the winter?
A: As of now, we're not sure. I am seeing some signs pointing towards a lack of an El Nino this year. However, climate models are keeping the Nino (albeit weak) through the fall and winter. The waters are pretty murky, so to speak, and nothing is set in stone.

Q: Is your Official Winter Forecast still valid after all this talk about no El nino?
A: For the moment, yes. I will make any big changes in the Final Winter Forecast, which will come out in late October or early November.

Q: So what should I think about the upcoming winter?
A: In a summary, cool and wet for the East Coast, slightly dry for the Midwest and portions of the Ohio Valley. Wet for the South, warm for the Northern Plains.

If you have any more questions, don't hesitate to ask them in the comments below.


Forecast Discussion for Sunday, September 23

Today's Weather Hotspot: Central Plains
Despite the presence of a cool high pressure over much of the central US, some spotty showers appear possible for the region. Additionally, a close proximity of a frontal system to the high pressure will create a windy situation for the region today. Bundle up and don't get blown away!

Great Lakes
Lake effect showers will be falling in the wake of a cold front that brings cool autumnal air into much of the eastern part of the nation today. The most intensely-hit areas will be the western Great Lakes, where some heavier precipitation should be observed.

South Florida
A disturbance in the region will provide ignition for showers and a possible storm. No severe weather is expected.

Western Rocky Mountains
A disturbance in the region will provide the base for some liquid precipitation. No severe weather is anticipated.

An incoming disturbance will provide some showers just offshore the region. A little moisture may reach the coastal regions, but other than that, conditions should remain dry.