Dan’s Wild Wild Weather Journal

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

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!

27 May, 2005

I showed some of our first echo id data on air at 10pm Thursday.(See the last blog)
Using ARMOR and it’s dual polarimetric capability, a computer program can be run to analyze the radar echoes using different variables like differential reflectivity and specific differential phase etc. (I have a link at the end that will explain these)

This program can then estimate whether the echo is rain..sleet hail etc. Truly the future of weather radar technology and I just bet I am the first person to ever show it on tv! (Something I care about and no one else!)

Missed it? Here it is (It will make sense when you look at it!)
HYDRO ID

A great web site on how dual polarimetric radar works is at this NSSL web site.

Our next goal is to be able to have this data in real time during severe storms.

Later,
Dan