As the hurricane hits New Jersey tonight just south of Manhattan, a good way to measure storm surge is to track tide heights.
Tides this morning at Sandy Hook, NJ were 3 foot above normal. High Tides will be even greater at 8:30 PM tonight , just before the storm hits, and afterwards at around 9:00 AM Tuesday morning.
This chart shows that the morning high tides were 8 feet above MLLW. Mean Lowest Low Water is the average of the lowest daily tide. The Blue line on the graph is the norm, the red is current. Today the high tide height was 8 feet above the low. Normally high tide is around 5 feet above the low. So this morning there was a 3 foot storm surge in Sandy Hook.
Now that we understand MLLW we can interpret these flood warnings. http://www.google.org/publicalerts/alert?aid=a1220a6e14dbe45f&hl=en&gl=US&source=web
For example Kings Point, NY is forecast to have a high tide 15 -16 above MLLW. Normally high tide there is around 8 feet above MLLW, so that represents a predicted 8 foot storm surge.
- Full moon could make Hurricane Sandy impact worse (cbsnews.com)
- Hurricane Track Has Shifted South, But Major Flooding Still Expected In New York And New England (spiceofyourlife.wordpress.com)