Dr. Jeff Masters' WunderBlog

Last Updated: 4:00 PM GMT on November 12, 2009 — Last Comment: 9:04 PM GMT on November 12, 2009

	Historic Nor'easter pounds Mid-Atlantic coast

Posted by: JeffMasters, 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.

Jeff Masters

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Updated: 4:00 PM GMT on November 12, 2009

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	Ida's remnants pounding North and South Carolina; El Salvador flooding toll at 160

Posted by: JeffMasters, 3:06 PM GMT on November 11, 2009

The remnants of Tropical Storm Ida have pushed off the coast of Georgia, and are adding fuel to a developing extratropical storm that is pounding North and South Carolina with heavy rain and high winds. Over two inches of rain has fallen across much of the region, and NOAA's Hydrometeorological Prediction Center (Figure 1) predicts that up to eight inches of rain could fall in coastal North Carolina by Saturday. Adding to the rainwater flooding problems from all thi...

Ida on Tuesday Pensacola Beach Pier

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Updated: 4:02 PM GMT on November 11, 2009

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	Ida pulls its punch; El Salvador floods kill 130

Posted by: JeffMasters, 3:01 PM GMT on November 10, 2009

A weakening Tropical Storm Ida limped ashore near Dauphin Island, Alabama at 5:40 am CST this morning, as a tropical storm with 45 mph winds. Winds at coastal locations during Ida's landfall were mostly below tropical storm force. One exception was Dauphin Island, where winds peaked at 40 mph, gusting to 50 mph, near midnight. Radar-estimated rainfall from Ida showed many regions received 3 - 5 inches of rain (Figure 1), which has caused some minor river and street ...

Tropical depression IDA

Tropical Storm Ida

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Updated: 8:50 PM GMT on November 10, 2009

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	Ida lashing the Gulf Coast; no change in strength

Posted by: JeffMasters, 12:16 AM GMT on November 10, 2009

Tropical Storm Ida is pounding the coasts of southeast Louisiana, Mississippi, Alabama, and the Florida Panhandle with high winds, huge waves, and heavy rain. At 6 pm EST, the Mobile, AL NWS office reported that coastal flooding had begun on Dauphin Island and at Fort Pickens in the Florida Panhandle. Surf heights of 5 - 8' are expected tonight on Dauphin Island as Ida storms ashore, and heights of 10 - 15' are possible from Fort Morgan, Alabama to Destin, Florida....

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	Ida not weakening; spreading heavy rains inland

Posted by: JeffMasters, 8:31 PM GMT on November 09, 2009

Data from the Hurricane Hunters this afternoon indicates that Ida has not weakened, and remains near hurricane strength. AT 3 pm EST, an Air Force airplane reported that the pressure had fallen to 991 mb, and a small area of hurricane force winds of 75 - 80 mph had developed in the outflow from a intense burst of thunderstorm activity on the southwest side of the eye. Surface winds elsewhere in the storm were 60 - 70 mph, so NHC decided that the hurricane-force wind...