JJS wrote:My wife works at NOAA, so I sent her the link to this comic with the subject, "Share with your weather buddies". Here is what she got back:
Cute, of course. There actually is some science behind this one. Beam filling is the proper term. I was taught to call it "The Tonganoxie Effect."
The radar beam is wider at distant points than it is at closer points. Thus, the resolution of radar data improves as a storm approaches the location of the radar. Precipitation lines that look threatening at a distance can actually "break up" and look more innocuous as they approach because of the sampling bias. It's easy to see on a single radar image, but modern mosaics can obscure it.
For years and years, instructors at the NWS Training Center in Kansas City, Missouri nicknamed this "The Tonganoxie Effect." Tonganoxie is a town a few miles west of Kansas City, Missouri. The joke, of course, was that something magic happened as a line of thunderstorms passed over Tonganoxie which caused the solid line to break up into smaller cells. The term was in common use at the Cleveland, Ohio weather office when I left in 1990.
Later . . . Jim
Hmmm, I hadn't given this any though. Of course, I'm still in college studying meteorology, so the forum members will need to take her knowledge on the subject as worth far more than mine. I think most people have hit the nail on the head with large cities, what we have observed to be the urban heat island effect. Owing to the large amounts of concrete, steel, glass, and asphalt in a large urban area, the region heats up more rapidly, retains more heat, and cools down more slowly. This is an easily observed phenomenon. Next time your local news shows regional temperatures, compare urban and suburban areas with rural temps.
However, there are many different reasons a storm will grow stronger or die out. Geography, lakes, boundaries between airmasses, local pockets of more dry/humid or warm/cool air, small regions of low/high shear... any of these can cause a storm to strengthen or weaken. One must also take into account the lifetime of a storm, which is dependent upon all of the above qualities, as well as the type of system that the storm is in (MCS, airmass storms, tropical, convective, stratiform, linear, etc). As one person mentioned, it would make a decent thesis topic, but would require a lot of observations... and not just at the surface. Radiosondes (weather balloons) are expensive, and, in order to achieve an accurate observation, must be launched relatively simultaneously. Currently, most locations only launch them at 12 and 00 Z (UTC), although some research locations (such as Boulder, CO in the US) launch them more frequently. The sheer logistics of getting a small resolution atmospheric profile is any meteorologist's dream, but the money and manpower just aren't there.
Regarding the storm motion: Systems in the US vary by region, season, and individual storms. A polar or Arctic airmass front can have a southward propagating line of storms in Texas, while the same system moves westward across Mississippi. It all depends. Generally, though, when the cells are linear north-south as they are, they'll move west to east in the continental US.