Dan’s Wild Wild Weather Journal

I write this on the coldest night of the Winter so far. Now before you start writing me an email me that it is not Winter yet, save your bandwidth. Meteorological Winter began on the first of December.

This week is going to be cold..as a matter of fact, another surge of cold air will come through on Wednesday night. By the end of the weekend, however, the cold will slip off to the East, and milder Pacific air will return. The long range guidance has been very consistent in indicating a pattern change across North America, and I think it has the right general idea.

Long range forecasters look at something called the North Atlantic Oscillation. The NAO is a pressure pattern over the Atlantic. The negative phase tends to bring cold air into the East. We have had a negative NAO for several weeks but it is now going positive. This should bring 2-3 weeks of milder air.

Don’t make the mistake of thinking this means a mild Winter is in the offing. Some of our coldest winters started in late December after a good long mild spell. There has already been a lot of cold air already. I was visiting my family in Tulsa over the weekend and when I arrived there was 10 inches on the ground. It was so cold that it was still there when I drove back to the airport last night! (they know how to drive on it back in Oklahoma by the way!)

So enjoy the return to milder weather starting next week. It is probably only temporary!

Later,

Dan

I hope you are enjoying this mild weather, because there is little doubt that it will come to an abrupt end late Thursday. Over the weekend, I saw some -40 readings up in N.W. Canada, and that air is still sinking southward.

Take a look at this link. It is a high definition camera on a mountain over the beautiful village of Banff in Alberta. I have been watching the Bow River freeze up as it runs through town. The low this morning there was -25C. About -15F.

http://www.banffgondola.com/live_cam.asp

The numerical weather computer models are bringing the front through the Tennessee Valley late Thursday night, into early Friday morning and I expect temps will slide slowly, during the day on Friday. Make no mistake though, the coldest air will slide north of us.

Arctic airmasses make for some tough forecasting because the real cold air is shallow and heavy. Weather models tend to push it down too slowly and out to quickly. More improtantly, the storm track pattern is changing and I think this is just the first surge of some arctic air. More to come! (Can you tell I like the cold? “wink wink” )

Will it be cold enough to snow-yes. Will it snow.. very unlikely but we might see some wet flakes before the air drys out behind the front on Friday. Don’t give up hope, if you are a snow lover.. winter is just beginning and I did not see an airmass this cold all winter last year! Mother nature is making a lot of it this year, and it usually ends up heading south!

Later,
Dan

In the last 30 days, we have added 3 major new computer and software systems to the weather office.

The first is a new weathenet system that allows us to show any and all of our weatherbug sensor stations. Along with this is a new weatherbug for our viewers. If you have not already downloaded it, it is on our weather page on whnt.com. Just put in your zip code and it will find your nearest weatherbug sensor. These are professional grade stations and the data is very accurate.

I have had some emails from a few people who have found that the weatherbug sets off their anti virus software. This is a known problem and be assured the weatherbug folks in Maryland would not allow something like that on their software.

We have also upgraded some software we have been testing to allow us to see radar images in 3d. We can now see what armor sees in 3 dimensions! With this software upgrade we started running our Armor radar in what we call a volume scan. It actually does scans 7-12 different angles as the antenna rotates. This gives us a view of the entire atmosphere within 100 miles(every 3 minutes!).

Not only is this valuable for real time severe weather forecasting but it will help our partners at UAH who use this radar for research. There are only 4 or so dual polarimetric radars in the USA and we have the only one in a television station weather office in the world. (Although I hear that several stations around the world are now looking at building one).

I will be presenting a paper on our radar to the American Meteorological Society conference in San Antonio in January.

Last and not least (Certainly most expensive!) we have upgraded our work station/graphics computer. You have probably noticed this with improved graphics. Actually you have seen just a fraction of this systems capabilities. We will show more as Winter comes on.

The biggest change we have made is to produce a more forecast driven weathercast for you. Instead of spending time on the weather that is happening now, we will focus on what will happen! This new system allows us to show you the actually computer models we look at each day. I can show you the model that I think is the most likely to be right and strip out the complicated Meteorology and just show clouds and precip. and or temps. (The Metr. stuff we need to see is still available for us and I may show some of it from time to time.)

The new 10 day forecast is a part of our “new look” and as I say each time I show it, the last 3 days are an educated guess and could change dramatically. Still, I feel that it has some forecast value as long as we warn our customers (That is you!) I will write my next blog solely on the 10 day forecast.

Later,

Dan

PS Thanks to all of you who emailed to say how much you enjoyed Elvis-it was a real hoot to do it!

Category: Forecast Center, Forecasting, Meteorology, Weather,

Well, we finally broke the heat wave. Many areas had some heavy rains over the last 48 hours as well, so that should make the farmers happy.

I have a tree in the yard that’s about 3 years old. It was almost dead from lack of water. After a good heavy rain Thursday night, it had perked back up nicely! I had been kicking myself for not noticing it, but the rains came just in time!

The damage may be done for many of the farmers in these parts. Several counties in the area are now classified as in severe drought now.

It might seem easy to classify a drought - just look at rainfall and perhaps temperatures, right?

It’s not that simple though.

Do you classify drought conditions based on rainfall for the past 30 days, or 60. What abut 90-180 days? Even rainfall over 6 months ago can impact crops. Some crops need more rain than others and some crops can handle a dry spell better than others.

You see it’s not really that easy!

There are several different drought classification methods in place. Each with their attributes and deficiencies.

One of the older ones is the Palmer Index. There are actually several different versions of it, but the main index is a long term index. The Palmer index will not change much for our area, in spite of getting 1-2 inches of rain late last week.

Below is the Palmer Index for July 2006:

There is a newer more experimental index that has been developed by the USDA and NOAA. This index reacts a bit more quickly to drought busting rains.

The link at the bottom of the image will take you the drought monitor web site where you can read more about how the chart is made.

One final note. The temperature is vitally important in a drought. In the winter, the air and ground are cold, and there is little evaporation from the soil. Just the opposite in the warm season. Evaporation rates are very high and plants are green. The high rate of photosynthesis and transpiration also uses up the soil water quickly.

This means that an inch of rain in January, will keep the soil wet much longer than even 2-3 inches of rain in early August.

It looks like we will go back to a fairly dry pattern next week (But not as hot!). The warm weather, and green plants will suck that moisture out of the ground quickly, and the soil will be bone dry again in just a few days!

The news media seems to love these long range hurricane forecasts. Dr. William Gray started forecasting the number of tropical storms and hurricanes in the Atlantic Basin over 20 years ago. NOAA in Washington has begun to make an annual prediction as well.

There is some good in these predictions. They get lots of attention, and hopefully get coastal residents thinking about what they would do if they were faced with an impending category 5, on their door step. That’s where the good ends in my opinion.

NOAA today and Dr. Gray last week revised down the number of storms expected this year. That did not surprise us in the weather office. JP, Spencer and I have all thought that it would be extremely unusual to have another record breaking year in the tropics. That said, we did, and still do expect an above average season. You will not see any forecasts like that from the WHNT weather center. Frankly, it is just not possible yet to make a prediction of how many storms will develop several months ahead of time.

A forecast of an above normal, or well above normal season, is not beyond current science, and most meteorologists I know will agree that an above normal year is still likely.

There are a bunch of factors that go into these forecasts. Some are obvious, like the sea surface temperature anomalies. If the water in the tropical Atlantic is well above normal then that would favor a more active season.

Another factor that is not so obvious, is the wind direction in the stratosphere above 75,000 feet. These winds tend to switch directions from West to East every few years. This is called the QBO or (get ready for it) the Quasi Biennial Oscillation. When the winds are strong from the East we tend to see considerably fewer tropical storms in the Atlantic and Gulf. This is likely because of the high wind shear in the Stratosphere. A Westerly QBO tends to bring an active hurricane season.

There are other factors as well, but suffice it to say- take these hurricane forecasts with a grain of salt. If you hear that we are expecting an active season- that is a forecast that will probably verify.

If you hear that we are going to have 9 hurricanes and 14 tropical storms, three of which will hit land-then do what I do-laugh.

Later,
Dan