Floods
Floods are the number one killer in the United States according to government statistics, accounting for an average of 100 fatalities a year and an average of more than two billion dollars in damage annually. And approximately half of all flood fatalities occur in automobiles. It can take as little as six inches of flowing water to float an SUV sized automobile, which is why you should NEVER drive into or across a flooded road.
In the Northeast, spring and especially summer thunderstorms can produce extremely heavy rainfall in very short periods of time causing rapid flash flooding. When tropical air migrates into the Northeast and the upper level steering winds are light or non existent, thunderstorms can form and remain stationary for several hours dumping inches of rain on a localized area resulting in flash flooding. One such event occurred during the evening of June 13, 2005, when localized torrential thunderstorms produced between five and six inches of rain in approximately three hours near Bolton Landing in Warren County. The torrent of water caused a severe flash flood that washed out and destroyed both the north and south bound lanes of Interstate 87, closing the highway between exits 23 and 25 for over a week.
Another local mechanism for producing flash flooding is the case where thunderstorms continuously form and move over the same areas, something called "Training of echoes" producing very heavy rainfall and flash flooding.
Tropical systems, such as topical storm Floyd in September 1999, occasionally produce excessive rain in the Northeast as well leading to both flash and large scale river flooding. Floyd in combination with a synoptic scale weather front, produced between four and fourteen inches of rain in eastern New York and western New England which caused significant flooding on some area waterways.
In the winter, floods can occur due to the combined effects of a rapid melt down of a snow pack due to a warm up and/or a significant rain system. This occurred on January 19, 1996 when a particularly deep snow pack was melted in approximately 24 hours by a major storm tracking west of the region. The storm track caused a strong southerly flow of wind pushing temperatures to around 60 degrees. The runoff from the snowmelt and heavy rain from the storm caused record flooding on many area rivers and streams.
Ice Jams are also a major cause of river flooding in New York and New England in some winters. Ice jams occur when thick river ice breaks up due to a warm spell or a rainstorm. The large chunks of ice can then jam on bridges and around bends in rivers, causing running water to back up behind the jam producing very rapid flooding.
Flash Flood Safety
* If you live in a flood prone area and thunderstorms are occurring you should always remain alert to changes in water levels and waste no time moving to higher ground if the water starts coming up.
* NEVER drive into or through a flooded road. It is impossible to know the depth of the water or strength of the current, especially at night. Approximately one half of all flash flood fatalities occur because people drive into flooded areas and their vehicles are then swept away.
* Outside or Camping: Know your campsite and its history to determine if the location is prone to flooding or not. If the site is prone to flash flooding, move to a safer location at the first sign of a thunderstorm in your area. In mountainous areas, it does not necessarily have to rain on your location for a flood to occur. If heavy rains occur over a ridge top, the runoff can inundate lower elevation areas close to but not directly under the thunderstorm. Many flood fatalities have occurred in mountainous areas due to upstream thunderstorms producing runoff floods catching victims completely without warning. This is a scenario that plays out frequently in especially the western United States, but can occur anywhere.
Flood Watch/Warning System
Local National Weather Service forecast offices will issue a FLOOD WATCH for a county or number of counties as much as twenty four hours in advance of a weather event that is forecast to produce conditions that could cause flooding. In this area, National Weather Service forecast offices in Burlington, VT, Albany, NY and Binghamton, NY issue flood advisories for the counties covered by the WRGB Channel 6 broadcast. A FLOOD WATCH means that conditions during a period of time are favorable for flooding either of small streams and creeks or major rivers. If you live in a flood prone area, it is during the WATCH period that you should prepare for the potential of flooding and put your safety and escape plan on standby.
A FLOOD or FLASH FLOOD WARNING is issued by the local National Weather Service forecast offices for counties or parts of counties when flooding is either being reported or Doppler weather radar is indicating that a sufficient amount of rain has fallen in a given period of time to push streams and rivers out of their banks. When the warning goes out you need to act immediately to move to higher ground. Very often, FLASH FLOOD WARNINGS are issued after flooding has begun, giving you little time to react. Therefore, it is critical for you to have a flood plan in place if you live in a flood prone area so you can take immediate action when the water begins to rise.
A RIVER FLOOD WARNING is issued for a main stem river, like the Mohawk, Hudson, Housatonic, Schoharie Creek, etc. Since mainstream rivers generally take longer to respond to a heavy rain or runoff event, flooding is often much slower to occur giving you more time to move out of the way. At the same time, the slow response from the major rivers can give you a false sense of security as was the case in January 1996 when the Hudson river flooded twelve hours after the rain had ended swamping hundreds of cars along river street in Troy. A flood warning had been issued, but the slow rise led many to believe that the river would not flood. You should note, though, ice jams can cause major rivers to flood very rapidly, leaving little time to take action.
Steve LaPointe
WRGB Chief Meteorologist
