Extreme rainfall = excessive water
Fri, 01 Oct 2010 16:11:49 GMT —
Believe me, it was very difficult to go on the air yesterday and forecast a widespread 2 to 4 rainfall event with a good chance for some isolated locations to receive as much as 6 of rain all within less than 24 hours. It is very rare for this type of event to occur. I have been warning people since Tuesday, and repeated the warning on Wednesday, that an unusual set of circumstances was coming together to give our area the risk for excessive rainfall leading to localized flooding.
It may be difficult to imagine 6 of rain. Think of it this way: if this was winter, and the exact amount of liquid precipitation was converted into heavy, wet, dense storm snow, I would have had to go on the air predict some of our area to receive 6 feet of snow in less than 24 hours. That's more than the blizzards of 1993 and 1966! For the record, colder air cannot hold nearly as much water through the atmosphere. Therefore, the exact same conditions would not have yielded the same amount of snow. Still, as a point of reference, it is interesting to think about.
The map that accompanies this story shows the Doppler Radar estimate of how much rain occurred for the storm. This is a good image to show, because it gives you a real feel and full coverage of how the areas was covered with heavy rain. Notice the yellow, orange and red colors. This corresponds roughly to areas that received 4 to 7 inches of rain in 24 hours or less. The red and even purple areas show the 7 maximum. There have numerous reports of flooded basements, road closings, and even mudslides in the worst hit areas.
As of late this morning, Delaware County, located just southeast of Otsego County and the Interstate 88 corridor, was under a county-wide state of emergency with all roads within the county closed. In addition, the worst hit areas of Cortland County were still experincing high water.
Further north in Oswego County, the Salmon River has been an area of concern, even before the rain began. On top of the normal rainfall and runoff, the dam floodgate had to release excess water. According to the National Weather Service, at 9:24 a.m. the dam operators on the Salmon River reported that the water being released from the Lighthouse Hill Reservoir had to be reduced to 8,000 cubic feet per second. While the amount of water was lower, the water level on the Salmon River remains very high from Bennett's Bridge downstream through Altmar and Pulaski and all the way down to Lake Ontario. Numerous roads along the Salmon River have been flooded and washed out due to the earlier heavier water release. Salmon and steelhead fishermen should remain well clear of the river today as fast moving water can sweep you downstream. In addition, numerous snags may be in the river. Further river flooding is expected in this area through the afternoon.
Here is a list of rainfall amounts we received from our weather watchers and from the National Weather Service:
...BROOME COUNTY... VESTAL 5.55 WHITNEY POINT 5.45 BINGHAMTON_S 5.31 BINGHAMTON REG 5.00 WINDSOR 4.57...CAYUGA COUNTY... AURORA 3.18 LOCKE 3.60 AUBURN 3.30 MARTVILLE 3.37 PORT BYRON 3.33 MORAVIA 3.27...CHENANGO COUNTY... SHERBURNE 4.20 NORWICH 4.01...CORTLAND COUNTY... CORTLAND 6.70 WILLET 5.26 MARATHON 3.50 ...DELAWARE COUNTY... HANCOCK 7.25 ANDES 6.17 DEPOSIT 5.80 ROXBURY 4.94 ...JEFFERSON COUNTY... WATERTOWN 4.19 LOWVILLE 3.62 CARTHAGE 3.28 THERESA 3.14 FORT DRUM 3.58 ADAMS CENTER 3.18 WATERTOWN AIRPORT 2.89...LEWIS COUNTY... CONSTABLEVILLE 4.38 PORT LEYDEN 4.05 HIGHMARKET 3.89 HOOKER 3.48 ...MADISON COUNTY... CAZENOVIA 4.52 LAKEPORT 4.35 CAZENOVIA 3.95 ONEIDA 3.84 NELSON 3.65 CANASTOTA 3.53 ...ONEIDA COUNTY... WHITESBORO 4.24 VERONA BEACH 4.20 POINT ROCK 4.21 ROME 4.06 HOLLAND PATENT 3.93 DURHAMVILLE 3.92 VERNON 3.83 WESTDALE 2.87 ...ONONDAGA COUNTY... FABIUS 5.40 TULLY 4.45 JAMESVILLE 4.12 CAMILLUS 3.65 DEWITT 3.20 CLAY 3.12...ONTARIO COUNTY... GENEVA 2.99 HONEOYE LAKE 1.99...OSWEGO COUNTY... PULASKI 3.95 SCRIBA 3.79 MINETTO 3.61 OSWEGO 3.51 LACONA 3.35 REDFIELD 3.30...OTSEGO COUNTY... MOUNT VISION 4.50 ONEONTA 4.50 WORCESTER 4.50 RICHFIELD SPRINGS 4.27 COOPERSTOWN 3.83 UNADILLA FORKS 3.44...TOMPKINS COUNTY... BROOKTONDALE 4.47 DANBY 4.10 NEWFIELD 3.97 ITHACA 3.91 FREEVILLE 3.83 TRUMANSBURG 3.83 GROTON 3.66 LANSING STN 3.32...WAYNE COUNTY... WOLCOTT 3.11 NEWARK 2.87 MARION 1.93 WALWORTH 1.79
Anyway, the steady, important rainfall is history. Therefore, additional rain will not make the situation worse. However, standing flood waters will take time to recede.
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