A tale of two storms

The mystical nature of tropical cyclones is that they even form at all. They begin as convective cells (what could be called large thunderstorms).  What appears to be a disorganized grouping of storm cells, can organize, begin spinning and in no time, appear to be a fully organized system. Of course there are very technical descriptions as to how this occurs, but from satellite imagery, it can be amazing to watch. While some of the larger convective (colder) cells can appear to be a separate system, they often are actually part of the original circulation. Here are a couple examples recently brought up on the talk forum at talk.cyclonecenter.org, both of which had two significant landfalls.

1989 Typhoon Gay

Time series of the winds associated with Typhoon Gay

Time series of the winds associated with Typhoon Gay

This system was interesting in that it is a system that began in the Gulf of Thailand – considered the Pacific Ocean – then moved west into the Indian Ocean, eventually making landfall in India as – potentially – a very strong cyclone. Of course I must qualify that statement because of the differences in the best track data. The graph at right shows the best estimates of the storm’s intensity, in maximum sustained wind speed. The system gained strength near day 2, then crossed into the Bay of Bengal and regained strength. At landfall in India, it was likely between 70 and 150 knots, kind of a large range. Some of these differences in intensity are due to the data available to each agency. Another could be in the interpretati0n of the imagery.

Typhoon Gay during development

Typhoon Gay during development

A recent talk post from ibclc2 noted the features in Typhoon Gay during its development in the Gulf of Thailand. The organization of the system is beginning to take shape. The convective cell  near B is close to a banding feature (if you were doing a detailed classification). But it is not, since the region between it and the central part of the system is not warm enough (it needs to be red or warmer, see the field guide for more information). The portion near A appears to be an embedded center. But upon further review, there appears a warm spot just north of the darkest blue colors. It could be the beginnings of an eye, but only time will tell … and it does. In the next few images, that small warm spot becomes an eye just prior to making landfall on the Kra Isthmus. So how would you classify it?  Well it’s likely best left as an embedded center with no banding. While there is the hint of an eye, the primary characteristics of an eye (cold cloud surrounding a warm center in a circular fashion) aren’t complete yet.

2005 Hurricane Dennis

Hurricane Dennis in the Caribbean

Hurricane Dennis in the Caribbean

An image of Dennis recently noted by bretarn showed a large system. Similar to Gay above, the satellite image showed a cold center (A) with a large cold band to the east. The convection near A is showing some circulation, so the center is somewhere below that cold cloud cover. So it is an embedded center. Like the Typhoon above, this is an image just prior to an eye emerging. The next question is what to do with B. It is definitely associated with the system, because it appears to be wrapping around the circulation center near A. The region between A and B is warm, with the warmest color being red. So for a detailed classification, this might be considered a banding feature.

In its own right, Dennis was a very severe system, making landfall in Cuba and in the Gulf on the Florida panhandle. However, its fast movement lessened the impact. It is also less memorable because its Gulf landfall was eclipsed by Hurricane Katrina later in the season. Nonetheless, the name was retired from the North Atlantic hurricane names after the season.

About K Knapp

I am a meteorologist at NOAA’s National Climatic Data Center in Asheville, NC. My research interests include using satellite data to observe hurricanes, clouds, and other climate variables. *******Disclaimer******* The opinions expressed in these blogs are mine only. They do not necessarily reflect the official views or policies of NOAA, Department of Commerce, or the US Government.

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