Wednesday, October 30, 2013
One thing I never really paid attention to coming into this class was the surface station models. They are helpful and all, but they are difficult to look at. I mean, take a look at this chart below. It’s ugly enough as is, and to think that it’s a simplified version of what is usually used… well… you can see why I’m not a big fan of them.
But they are an essential part of communicating weather observations, so let’s take a look at some!
Above is a wonderful graphic from a PDF put together by Professor Houze himself. Some parts of the diagram are is pretty self explanatory, but there are several more advanced features, namely pressure, wind, cloud cover, and “current weather”. Temperatures are in Fahrenheit.
The pressure is not 138 mb. Atmospheric scientists are too lazy to add that 10 at the beginning. However, if the pressure reads something like 999, that DOES NOT mean that the pressure is 1099.9 mb. My head might very well explode under conditions like that (not really, but no atmospheric pressure ever recorded on Earth is that high). Instead, you add a 9 to the beginning. Determining whether to add a 9 or a 10 is pretty easy, and although there are situations where there could be an overlap (for example, 400 could correspond to 940 for a tropical cyclone or 1040 for a strong ridge of high pressure), you can just look at nearby stations and other indications on the map to get an idea of what the prefix is.
Wind is not measured by numerical units. Instead, we have barbs. Small barbs are equal to 2.5 m/s, while large ones are equal to 5 m/s. When it gets really windy, we also use flags, which are equal to 25 m/s. The diagram below shows a nice example of some different wind barbs. However, keep in mind that the below one uses knots. To get meters/second, just divide knots by 2. If we tried to use knots for that intense 150 knot jet at the 200mb level of the atmosphere, we’d only be making a bad situation worse.
|Retrieved from the “Weather Informer” blog – http://brianmejia.wordpress.com/terms-concepts/|
Cloud cover is denoted by that circle at the middle. In the example above, it is black, but it is not always black. The chart below is pretty self explanatory. “Sky obscured” generally means fog, although I guess it could represent a cumulocannibis cloud arising from one of the bored forecasters at the airport as he toked up while simultaneously taking cloud observations. You think all the fog lately has been because of an inversion? Maybe, but let’s just say there’s a little more particulate matter there this year than last year.
|Retrieved from http://weather.about.com/od/forecastingtechniques/ss/mapsymbols_4.htm. Yes, about.com is legit.|
Temperature, wind, and all that jazz are all very nice, but we want to know what’s actually happening at the station. And that’s where the current weather symbols come in. These symbols generally let us know what’s happening precipitation-wise. Take a look below.
|Retrieved from http://www.hpc.ncep.noaa.gov/html/stationplot.shtml|
If none of these are happening (ex: the sky is clear and sunny and there are no crazy dust devils or haboobs going on), I wouldn’t be surprised if this part is simply omitted. But I don’t know for sure. Here’s what the NWS claims to be signals they claim to use 99% of the time.
I’d definitely practice the surface station model stuff for the test, there could very well be a question on it. On to the next blog!