Hurricane Irene -- Telling The Story Through Wind Data
When Hurricane Irene blew up the U.S. northeastern seaboard late this summer, she left devastation in her wake. She wreaked havoc in the Carolinas and Virginia, made a very light pass over Second Wind HQ in the Boston area, and washed out homes, roads, buildings, and bridges in Vermont and New York.
Second Wind's SkyServe Wind Data Service displays wind data from Triton Sonic Wind Profilers and tower-mounted sensors. Because a hurricane is such a dramatic weather event, looking at the wind data from Irene on SkyServe highlights meteorological features of a hurricane. As luck would have it, Second Wind has a Triton sodar deployed on Cape Cod and we got a Triton's-eye view of the hurricane.
First, What's A Hurricane?
A hurricane is a tropical cyclone with a large low-pressure center with higher temperatures than its surroundings. The winds flow counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. Because warm water is their main source of energy, cyclones occur most frequently in the summer and are strongest over the ocean. They weaken over land because of the lack of warm water and the added surface friction of the land. For this reason, tropical cyclones do their worst damage in coastal regions.
A hurricane has three major parts: the eye, the eye wall, and spiral bands of rain clouds surrounding the eye wall. The eye of the hurricane is the calmest area of the storm - an empty hole, often with clear skies overhead, measuring 20-50 km in diameter, and with the lowest pressure reading ever recorded on a barometer. The eye wall is the most dangerous part of a hurricane, with extreme winds, thunderstorms, clouds, and rain. Outside of the eye wall there are spiral bands of rain clouds.
Finding the Hurricane in August
If you were fortunate enough to escape Irene's severe consequences, you probably don't remember exactly when she blew through town. A quick look at our Triton's data for the month of August tells the story.
From the high wind speed, characteristic change in wind direction, and low pressure towards the end of the month, we can tell that the hurricane was near our Triton on August 28. The clearest indication of the storm is the dramatic drop in barometric pressure. Looking at the Standard Data screen and adjusting the timeframe, we can see that the barometric pressure measured by our Triton began to drop at 8 pm on Saturday (00:00 on Sunday August 28 in UTC) and was back to normal at 8 am on Monday, August 29.
Weather data showing the path of the storm center confirms that Irene (downgraded to a tropical storm by the time she made landfall in Massachusetts) was closest to our Triton during the day on Sunday.
Wind Speed
The graph of wind speeds shows that the high wind speeds in the middle of the day Sunday correspond to the low barometric pressure -- and there was also a fair bit of shear, or difference in wind speeds measured at different heights.
Wind Direction
The wind direction data gathered on Sunday tell the story of a hurricane with counterclockwise wind flow. As Irene was southwest of our Triton, the Triton was recording the east-southeast winds that were blowing at the northeast edge of the storm. After Irene had moved north, our Triton was recording the west-southwest winds from the southeast edge of the storm . . . and so on. SkyServe's time stamps are all in universal time code (UTC), so you need to adjust for local time.
We Are Wind Geeks
Second Wind's support team keeps an eye on the news just the way anyone else does. We definitely alerted our Triton customers with units in or near the storm that the hurricane was coming. Asked what special preparations the Triton needed, Tim Clarke, Second Wind's support manager, answered: "No special preparations. We just told them it would be really cool to watch on SkyServe."
