Hurricane Sandy 's "perfect storm" threat to the East Coast is drawing worldwide attention to forecasting by both the National Hurricane Center and the local forecasting stations of the National Weather Service. I've put together some basic tips on how to look for information on the web as Sandy approaches the New Jersey coastline overnight. First, a bit of...
Hurricane Sandy 's "perfect storm" threat to the East Coast is drawing worldwide attention to forecasting by both the National Hurricane Center and the local forecasting stations of the National Weather Service. I've put together some basic tips on how to look for information on the web as Sandy approaches the New Jersey coastline overnight.
First, a bit of basics about why Sandy has been dubbed a "Frankenstorm" by the media, with assistance from Barry Keim, Louisiana State Climatologist, who is at Louisiana State University:
"We have a tropical hurricane merging, or folding in, with a mid-latitude weather system, one of those low pressure systems that track across the country," Keim explained. "The two systems' dynamics are very different and when they occasionally fold together, they actually produce the worst characteristics of both."
That includes storm surge that usually accompanies a tropical system, with up to 11 feet predicted for New Jersey and New York, including Manhattan, and the prospect of 2 to 3 feet of snow in West Virginia.
These kinds of storms typically occur in the fall, when frontal systems built around mid-level low pressure areas begin marching across the United States, pushing cooler, drier air capable of producing snow, at the same time that ocean temperatures in the tropics remain warm enough to fuel a hurricane, he said.
"This is the same thing that happened during the perfect storm of 1991, and at roughly the same time," he said. Before the movie of the same name documented that storm's effects on the hapless Andrea Gail, a swordfishing boat based in Gloucester, Mass., that weather system was known as the All Hallow's Eve Storm.
But Sandy also is different in its size, rivaling the largest cyclones ever recorded around the globe, Keim said, with hurricane-force winds extending outward 175 miles from its center and tropical storm-force winds extending out 485 miles. That's why forecasters are warning repeatedly that people should not focus on the skinny black line indicating the path of Sandy's eye.
Sandy's track also is problematical, especially for the threat of storm surge. Normally, storms that threaten the East Coast move parallel to land in an arc, leaving the strongest quadrant of the cyclone offshore, points out LSU graduate student Hal Needham in his "Hurricane Hal's Storm Surge Blog."
But Sandy is forecast to move due west into the coastline, with its strongest winds, and highest surges, pushing into the L-shaped area formed by the coasts of New Jersey, New York, Connecticut, Rhode Island and Massachusetts.
And then there's the unusual wind patterns that the National Hurricane Center has tracked during Sandy's move towards shore. Over the past few days, research planes traveling through the system have found high winds near the on-again, off-again eye at Sandy's center, but have found equally high or higher winds well away from the eye.
According to the Multiplatform Tropical Cyclone Surface Winds Analysis conducted by Colorado State University and the National Weather Service, an elongated area of 50-knot winds was already near the shorelines of New Jersey and New York this morning, well ahead of Sandy's center.
Here are some tips for searching for information about Sandy:
The main forecast from the National Hurricane Center. This link leads you to the graphics page, which includes links to rainfall potential, warnings map, and wind speed probabilities.
The public advisory is the best compendium of general information about Sandy until it moves ashore, but go to local NWS sites for detailed information, including more specific information about how surge will affect a specific location. Generally, a browser search using the city name, state NWS and forecast will lead you to that site.
For instance, when you go to the Manhattan, N.Y., site, a coastal flood warning message warns of high surf along ocean facing shorelines this afternoon into the night, including breaking waves building to 15 to 20 feet. Waves of 6 to 12 feet are expected along exposed eastern and northeastern facing portions of Long Island Sound, Peconic and Gardiners Bay, and New York Harbor.
"The destructive waves on top of the storm surge will cause overwashes and significant damage to coastal structures nearest to sea level," reads the warning message. "This is especially true for low lying areas along Ocean Parkway and Dune Road, the Twin Forks of Long Island, Fire Island communities such as Fair Harbor, Ocean Beach, Cherry Grove, Fire Island Pines, and Davis Park, and historically vulnerable locations along Long island Sound."
A reminder that surge refers to the "stillwater" rise of water in advance of a storm, which will be topped by waves that can be a third to half as high.
You can also find additional surge and tide information from the NWS Meteorological Development Laboratory by clicking on a location on the regional map, although the site is still in development and the exact heights listed in its predictions have not necessarily been updated to reflect changes in local sea level heights.
NWS web sites also often have a local storm report page that lists information that forecasters have received from calls from the public or from local emergency management officials. The location of this page on the local web sites varies, but the link often is listed on the page where residents are asked to submit their reports.
Here's an example from the main New York City site: The New York Fire Department reported that water rescues were occurring at Atlantic Beach at 10:30 a.m. today.
A national compendium of storm reports also is available.
Sandy also is likely to deliver heavy rainfall beyond the coast, which could lead to high river levels and interior flooding. To track rainfall, go to the NWS Precipitation Analysis Page. River level observations also are available.