Tonight we will take a look at hurricanes and the dangers they pose to New England.
The United States began naming hurricanes in 1953. Names were used to reduce confusion when two or more tropical systems were in existence at the same time. Female names were used for many years.....but with increased pressure to be politically correct...male and female names were used from 1979 to the present.
Hurricanes form over warm ocean waters....which have to be at least 78 deg or warmer. They form between 10 and 30 degrees latitude...as they need the effects of the coriolis force to help get organized and to assist in their initial circulation. Powered by the heat from the sea, they are steered by the easterly trade winds...and in later stages...by the temperate westerlies as they move into higher latitudes. Unlike other weather systems...their size and energy allow them to move somewhat on their own as well. Most hurricanes range from 300 to 700 miles in diameter...with effects on winds and waves extending thousands of miles in some cases.
Hurricane season in the Atlantic Ocean runs from June 1st
through November 30th...although hurricanes have been known to form in December.
Hurricanes and tropical storms differ from the normal storm system in several ways. For instance...hurricanes and tropical storms have no fronts. Their winds weaken with height. The centers of hurricanes are warmer than their surroundings. Hurricanes and tropical systems form under weak high-altitude winds. Air sinks at the center of the hurricane...thus the calm conditions and somewhat clear skies associated with the eye of a hurricane. A hurricanes main energy source is the latent heat of condensation. Hurricanes weaken rapidly over land.
Severe weather associated with hurricanes includes; Storm surge...storm tide...high winds...Tornadoes...and especially heavy rains and floods.
Storm surge is a large dome of water that sweeps into the
coastline near where the hurricane makes landfall...on the right side of the hurricanes
eye. This surge of high water topped by 6-12 foot waves is devastating. The stronger the
hurricane and the more shallow the offshore water, the higher the surge. Along the
immediate coast, storm surge is the greatest threat to life and property.
If the storm arrives at the same time as high tide...the height of the water will be even greater. The storm tide is the combination of the storm surge and astronomical tide.
Hurricane force winds, 74 mph or greater, can destroy poorly constructed buildings and mobile homes. Debris, such as signs...roofing material...siding...and small items left outside become flying missiles in a hurricane.
Widespread torrential rains often in excess of 6 inches in less than 12 hours can produce deadly and destructive floods. THIS IS THE MAJOR THREAT TO AREAS WELL INLAND.
Hurricanes also produce tornadoes. The tornadoes occur in thunderstorms embedded in the rain bands well away from the center of the hurricane.
New England feels the effects of hurricanes on average once every three years. Since 1900, 33 tropical cyclones have impacted the region, 24 as hurricanes. 9 of these hurricanes made landfall on the New England coast.
15 tropical cyclones caused inland flooding in rivers and streams. In the hurricane on 1938, up to 17 inches of rain fell across southern New England in less than 48 hours. Slow moving tropical storms can dump over 25 inches of rain over a five day period.
Of the 9 hurricanes that made landfall in New England, 4 were Category 3 in intensity. Storm surges ranged from 8 to 12 feet along the south coast, and 15 to 25 feet over portions of the north shore.
The strongest sustained wind associated with a hurricane in New England was 121 mph, and the strongest gust was 186 mph.
Southern New England is susceptable to all three hurricane threats: coastal inundation due to storm surge, inland river flooding, and wide spread wind damage.
This script, along with all of the others scripts used in this training, can be found at: http://www.qsl.net/kb1dfe.