Milutin Who???

I meant to update this blog sooner than this but I have been studying for a Historical Geology Final- It's been a real bear.

Some odds and ends on my mind tonight:
The Mets. over at Huntsville NWS went out and did a storm survey of Dekalb county after Friday's storm and upgraded the severe thunderstorm to an F zero tornado.Look for a pic of the wall cloud over Fort Payne on our web site picture gallery.

I'm planning a series of BLOGS on global warming.
There is so much confusing info out there, I think it would be a good idea to write up what is known with a high degree of certainty first. I expect to take some heat though. It seems a lot of people get there science on global warming (either view point) from talk radio hosts these days...

On the subject of planetary climate, Lets mention an almost forgotten scientist. Milutin Milankovitch.
Back inthe 1920's he proposed a theory for explaining the glacial cycles that show up so clearly in the rock record.

Milankovitch cycles are based on 3 variations in earth's orbit.

1.ECCENTRICITY- which varies on a 100,000 year cycle

2. OBLIQUITY. Which causes the seasons
(presently at 23.5 degrees) This is a 41,000 year cycle

3. PRECESSION: The changing of the dates of the seasons.
Right now Dec. 21st is the beginning of Winter, when we are closest to the sun. In 11,000 years it will be June 21st. When we are farthest from the sun.

This theory is still controversial among researchers, but most think it has a lot to do (in one way or another!) with the coming and going of the ice sheets over the continents.

The Naval Observatory has a good explanation of these cycles on it's web site. I have linked directly to it at the top of this blog.Click on LINK.

Over the last 250,000 years..the earth has been a snowball most of the time and we may very well be headed back that way again...well after the ice caps melt from global warming and Birmingham is ocean front property..but I will save that for another blog...

Stormy Weather and Screaming Sirens

Looks like we will see a significant severe weather event on Friday. Even the risk of some tornadoes is a bit higher than I thought earlier in the day. Then come a real cold snap!

Right now it still looks to me as if mid 30's are likely Sunday morning. On Monday with calm winds the cold pockets in Dekalb and Jackson counties may very well see some frost. In case your wondering, the latest freeze on record for Huntsville is May 2, 1909.

The severe storms have got me to thinking about an issue that is getting more attention lately. The criteria for Severe Thunderstorm Warnings.

Presently a severe thunderstorm is defined as winds greater than 55kts (58mph) and hail greater than 3/4inch in diameter.

However, research has shown that damage from hail does not really start until the hail size reaches 1 inch and even then it is not common.

This issue was discussed at a weather conference I attended a couple of years back. If the criteria were raised to say 1 inch hail and winds greater than 60 mph, there would be fewer warnings and the ones that were issued would have more impact.

I come down on the side of changing the criteria. I do not like to break into programming for a severe thunderstorm warning with penny size hail. It rarely causes damage.

Changing the criteria would mean fewer weather alert maps on the screen as well...that is a real plus!
(An NWS office in the Midwest is presently issuing severe warnings on the higher criteria on an experimental basis.)

It will require a real effort to educate the public though. I very frequently get calls from viewers who want to know why I haven't broken into programming when they are getting dime size hail and 50 mph winds. When I explain that the storm they are experiencing is not severe, I'm usually met with great skepticism.

No warnings are presently issued for lightning, but it kills more than tornadoes in most years!. I now will crawl a warning to viewers if I see a storm with a very high flash rate moving into a dense population area (That usually causes power outages)

One last thing while we are on the subject...
Tornado Sirens

They cost a bundle.
They're 1920's technology
-and think to yourself, how many times was your first warning of severe weather from a siren?? Very few I suspect.

Usually people hear the tornado warning on TV or radio and run out into the yard to listen to the sirens!
Something is wrong here.

I did the math one time and figured out that for the cost of a new tornado siren, you could buy everyone within the sound of it a NOAA weather radio with money left over!

Yes, there are a few cases where they may do some good...but the question is-
Can you justify the expense when more technologically advanced methods of warning are now available??

That and every community has a different standard for setting them off. I no longer make "siren announcements" during severe weather coverage..I have more important information to pass on.