Environment

A "Midget" Typhoon? Who Knew?

ImaGeo iconImaGeoBy Tom YulsmanJul 19, 2013 4:39 PM
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An animation composited of six images from NASA's Aqua satellite shows a possible midget cyclone cruising across the western Pacific. The Philippines are at the lower left of the frame, and the possible cyclone starts in the upper right. (Images: NASA) Because I'm such an unabashed weather geek, I check in most days with the awesome blog of the Cooperative Institute for Meteorological Satellite Studies. This morning was no exception, and what I found was a short post about a possible midget typhoon in the western Pacific Ocean. Who knew that such a thing existed?

Source: CIMSS Satellite Blog At the top of their post today, CIMSS ran an animation of the possible midget typhoon from Japan's MTSAT-2 satellite. Click on the thumbnail at right to see it full size. With that as a start, I thought I'd try to find it in images captured by NASA's Aqua satellite. The animation at top shows what I came up with. Click on it to see a larger version. The animation consists of six separate frames, each taken on a different day. (Please note that the distracting black bands could not be helped — they are areas that Aqua did not image in its passes over that part of the Pacific.) The sequence begins with the possible typhoon in the upper right. The outline of the Philippines can be seen in the lower left. That first frame is from July 14. In succeeding daily frames, the compact swirl of clouds cruises westward until the last one, captured today. The possible typhoon is, well, quite small. So if at first you don't see it, keep watching the animation and look for a little cyclone cruising across the top half of the frame. So, what's a midget typhoon? Let's start with nomenclature... "Typhoon" and "hurricane" both have these defining characteristics: a large-scale, non-frontal, low pressure system over tropical or sub-tropical waters that features organized thunderstorm activity and a closed pattern of wind circulation around a well-defined center. In other words, they are really different words for the same thing: a tropical cyclone. Typhoons are tropical cyclones that form in or move into the western North Pacific Ocean west of the dateline. The word "hurricane" is applied to cyclones in the North Atlantic, Northeast Pacific east of the dateline, or the the South Pacific Ocean east of 160E. (For more information, see this FAQ from NOAA's Hurricane Research Division, and this one from the National Weather Service.) Lastly, what about that "midget" designation? It turns out that tropical cyclones come in a variety of sizes. According to the U.S. Naval Meteorology and Oceanography Command, the very largest span more than 8 degrees of latitude. Each degree is about 69 miles, so these monsters are more than 550 miles wide. A medium size cyclone spans 3 to 6 degrees, or about 200 to 400 miles across. And to be considered a "midget," a cyclone must be less than 2 degrees, or about 140 miles across. Just because a cyclone may be a midget doesn't mean that it's weak. Research has shown that the size of cyclones is only weakly correlated with their intensity. That said, a large, lumbering cyclone with winds of equal intensity can still exact a much higher destructive toll upon landfall. That's because it will blast a much larger area with high winds and for a longer duration. Also, because its winds cover a much broader swath of ocean, its "fetch" is greater, and this typically results in more intense storm surge.

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