Weather Q & A - Round One

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May 29, 2:15 PM

by Tony Hake, Denver Weather Examiner

 

 

Yikes! You’re asking me to second guess the big guys at the news stations and with the National Weather Service in Boulder. I certainly would never pretend to be on par in knowledge with them but of course I have the benefit of hindsight now so I can look pretty brilliant.

I presume you are talking about March 16 - 19, 2003. This was actually one of the most bizarre and peculiar storms to hit the Front Range – somewhat the proverbial “perfect storm.” March 16^th dawned as a beautiful day and we were seeing 60 degrees by noon. The next morning though clouds started to thicken and by the afternoon thunderstorms were producing rain, hail and even a short-lived tornado east of DIA. Soon thereafter, snow started falling and it did not end until the 19^th. By that time southwestern and western Denver had 3 – 4 feet of snow; over 31” at the official measuring station at Stapleton. 

This storm was the result of a number of factors. A low pressure system developed and stalled over the southeastern corner of the state. As it sat there, it fed off the cold air coming from the north and the wet air coming from the Gulf of Mexico. As the jet stream passed over, a circular motion in upper level winds setup spinning the air and causing it to move extremely slowly, nearly coming to a halt over the metro area. As it sat there being fed by the cold, wet air, snow continued to fall for three days. Why didn’t the forecasters see this at the time? It is simply a factor of Colorado’s unpredictable weather. That low that parked itself over southeastern Colorado simply was not expected to stay there.

Certainly there is no doubt that Colorado is colder than Florida – I can’t argue there. As for New York, a quick look at the numbers is kind of interesting. 

What these numbers show us is that the average high temperature in Denver is actually warmer than New York Central Park in 10 out of the 12 months out of the year. Conversely though, Denver’s low temperatures are indeed colder than New York’s. So we are colder at night but warmer during the day generally. This highlights the large difference that we see in Denver between nighttime and daytime temperatures which probably is why it seems like we are colder. We simply don’t have the benefit of an ocean nearby to help stabilize and moderate temperatures like those along the coasts do.  An interesting side note...  Across the 12 months, Denver's average high temperature is 64.2 while New York's is 62.3.

As for the 80 degree question… Statistically speaking, Denver begins to average high temperatures above 80 starting June 8^th and lasting through September 8^th – four full months. However, 80 degree days have been seen as early as March 20^th (1907) and as late as November 8^th (2006).

A myriad of factors contribute to Colorado’s weather. As an inland state it is as much a factor of geography and topography as much as anything. We are over 1000 miles from a major body of water and that causes our rather arid climate as moisture in the atmosphere just doesn’t make it this far inland as much as we would probably like. During the winter the path the jet stream takes oftentimes brings that cold, Arctic air from the north and moist air from the Pacific can make its way from the southwest to cause the big winter storms we see. 

My crystal ball is in the shop this week but let me take a stab at the first part. Overall, nationwide, 2008 has seen a significant increase in tornado activity in comparison to the last three years. 1,199 tornadoes have been reported as of yesterday – that is more than the total for the entire years of 2007 and 2006 and nearly as much as in the entire year of 2005. However, these numbers are preliminary meaning the National Weather Service has not completely vetted and analyzed them and when the official tally is reached the number will most likely drop, possibly by as much as 20%. This is a result of tornadoes often being double or triple reported by multiple people viewing the same storm from a different location. For instance, one local news station at one point during last week’s event was reporting up to eight tornadoes. We now know there were most likely only three or four. 

Tornado statistics have only been tracked since 1950 so we have a relatively short period of time to be able to look back on and analyze trends. Further, today we have a number of things that allow us to see and record tornadoes that we most likely would not have been aware of even 10 or 20 years ago. Advanced weather radar can “see” tornadoes when they happen. Before this technology was available, if these storms occur in a remote, rural area, they most likely would never have been recorded. Further, as population increases, there are simply more people around to spot these storms. It is my opinion that yes, we may actually see more reports of tornado activity in Colorado than in years past but this is simply because we have the ability to see storms that we could not previously – not because of some greater increase in the actual occurrence of the storms. 

Tornado and alert sirens do exist in some municipalities in the Denver metro area but not all. Boulder has a system (primarily due to flood dangers) as does the city of Denver itself. Many of the other suburbs however do not. For instance, Thornton, where I live does not which to me is somewhat odd as in 1982 Thornton was struck by one of the few tornadoes to have hit the metro area so you would think that would have caused them to consider building a system back then. I would recommend you contact your local municipality to find out for sure.   

Probably the best way to ensure you are warned about approaching dangers is to purchase what is commonly known as a “weather radio.” These radios are relatively inexpensive (around $40.00) and allow you to listen to and monitor the NOAA Weather Radio All Hazards (NWR) system. NWR broadcasts official Weather Service warnings, watches, forecasts as well as other hazard information like earthquakes, avalanches, chemical spills, and even AMBER alerts. These broadcasts continually run 24 hours a day, 7 days a week and provide a great way to stay up to date with developing weather conditions. Some of the nicer units even use what is called SAME - Specific Alert Message Encoding – which I would highly recommend. In essence you program in a code for the area in which you live and the radio will automatically turn on and sound an alert when something of note is in your area. These weather radios are very popular in rural areas in Tornado Alley but as we saw last week, they definitely can be useful here along the Front Range as well. More information about the system can be found on the National Weather Service’s website and you can find these at many electronics retailers, particularly those on the Internet like Amazon or NewEgg.

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