Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 3:55 PM GMT on November 12, 2009
A historic Nor'easter, energized by the remains of Hurricane Ida, is pounding the coast form North Carolina to New Jersey with heavy rain, tropical storm-force winds, and a destructive storm surge. Wind gusts of 64 mph were reported at the Chesapeake Bay Bridge Tunnel and at Cape Henry, VA this morning. The high winds, combined with the slow movement of the Nor'easter are acting to push near-record storm surges onto the coast in Virginia, Maryland, and Delaware. At Norfolk, Virginia, the storm surge from Ida-ex was 5.0 feet at 10 am EST, the third highest storm surge there since tide gauge records began in 1927. Only Hurricane Isabel in 2003 and the Chesapeake-Atlantic Hurricane of 1933 have brought higher storm surges to Norfolk. Serious coastal flooding is occurring from northern North Carolina to the Delaware/New Jersey border, and the storm surge at Lewes Point, Delaware at 10 am this morning was 4.0 feet, just below the record high of 4.17' set during the January 4, 1992 Nor'easter. Tide records go back to 1919 at Lewes Point.
Figure 1. The Ida-ex Nor'easter at 9:31 am EST 11/12/09. Image credit: NASA/GSFC.
The highest storm surges on record at the Sewell's Point tide gauge in Norfolk, Virginia are:
5.62' Sep 2003 Hurricane Isabel
5.61' Aug 1933 Chesapeake-Atlantic Hurricane
5.00' Nov 2009 Ida-ex
4.73' Sep 1933 Hurricane 13, Cat 1
4.66' Mar 1962 Ash Wednesday Nor'easter
4.05' Sep 1936 Hurricane 13, Cat 2
And the highest water levels, measured above Mean Lower Low Water (MLLW, the lowest tide measured in a full 19-year natural tidal cycle):
1933 hurricane (Aug 23rd 1933)..............8.9 feet MLLW
April 11th 1956 Nor'easter..................8.0 feet MLLW
Hurricane Isabel (Sep 18th 2003)............7.9 feet MLLW
Ash Wednesday storm (Mar 7th 1962)..........7.8 feet MLLW
The water level during high tide this morning at 5 am EST reached 6.7' MLLW in Norfolk at Sewell's Point, but the storm surge of Ida-ex has increased by a full foot since then. The next high tide at 5 pm may see water levels near 8.2 feet. The tremendous amount of rain Ida-ex is dumping over the coast is adding to the storm surge, since the drainage of the rivers into the coastal bays raises the water level above what the wind pushes in.
Figure 2. Predicted storm tide (height above Mean Lower Low Water (MLLW, the lowest tide measured in a full 19-year natural tidal cycle, black line) for Sewell's Point, Virgina in Norfolk, as predicted by the GFS model. A storm tide of 8.0 feet is forecast this afternoon during the 5 pm EST high tide. For a full description of this plot, see the NOAA Extratropical Surge web site.
Figure 3. Tide gauge trace from the Sewell's Point gauge in Norfolk, VA, shows a storm surge of 5 feet (green line) at 10 am EST, and a maximum tide of 6.7 feet above MLLW so far today. Image credit: NOAA Tides and Currents.
Figure 4. Radar-estimated rainfall from the Norfolk radar shows a large area of 4 - 5 inches of rainfall over coastal Virginia and North Carolina. The band of very high rainfall amounts of 5 - 8 inches shown in the northeast part of the radar display is not real; rainfall amounts in that region have been closer to 2 - 4 inches. The error results because at that distance from the radar, the beam is about 8,000 feet above the ground, and is hitting a "bright band" of highly reflective precipitation, where snow is melting and forming rain. The highly reflective rain/snow area reflects much more of the radar beam back, making the software algorithm used to estimate precipitation amounts fail.
You can follow the storm today with our Severe Weather Page.
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