Skip Navigation Links   
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
National Hurricane Center
Local forecast by
"City, St" or "ZIP"

Alternate Formats
   Text     |   Mobile
   Email   |   RSS XML/RSS logo
   About Alternates
Cyclone Forecasts
   Latest Advisory
   Past Advisories
   About Advisories
Marine Forecasts
   Atlantic & E Pacific
   Gridded Marine
   About Marine
Tools & Data
   Satellite | Radar
   Analysis Tools
   Aircraft Recon
   GIS Datasets
   Data Archive
   Forecast Accuracy
Outreach & Education
   Storm Surge
   About Cyclones
   Cyclone Names
   Wind Scale
   Most Extreme
   Forecast Models
   Glossary | Acronyms
   Frequent Questions
Our Organization
   About NHC
   Mission & Vision
   Staff | Q&A
   Visitors | Virtual Tour
   Library Branch
   NCEP | Newsletter
Contact Us
Follow the National Hurricane Center on Facebook Follow the National Hurricane Center on Twitter
Subscribe the National Hurricane Center on YouTube Read the National Hurricane Center Inside the Eye blog on WordPress is the U.S. Government's official Web portal to all Federal, state and local government Web resources and services.

Tropical Cyclone Storm Surge Probabilities



The Tropical Cyclone Storm Surge Probabilities (P-Surge 2.0) is a graphical product developed by the Meteorological Development Laboratory (MDL) of the National Weather Service (NWS), in cooperation with the NHC, with the intent to provide the emergency management community; federal, state, and local government agencies; media; maritime interests; and the general public with information that enhances their ability to make preparedness decisions specific to their own situations with regards to storm surge. The Tropical Cyclone Storm Surge Probabilities product was created in response to user requests for additional tropical cyclone probabilistic information, and the National Research Council's Fair Weather Report encouraging probabilistic products.

Product Description

The Tropical Cyclone Storm Surge Probabilities graphics show the overall chances that the specified storm surge height will occur at each individual location on the map during the forecast period indicated. The probabilities are based on errors during recent years in the official track and intensity forecasts issued by the NHC. Variability in storm size is also incorporated. Storm surge values used in the calculations are produced by the Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model.


The calculation of the Tropical Cyclone Storm Surge Probabilities is accomplished by statistically evaluating a large set of SLOSH model runs based on the current NHC official forecast, and taking into account historical errors in official NHC track and intensity forecasts. Track forecast errors are considered in terms of both along-track (i.e., forward speed) and cross-track (i.e., landfall location) errors. The astronomical tide is explicitly modeled in P-Surge 2.0, which means that the timing of cyclone landfall relative to the tidal signal (i.e., along-track variability) is fully captured in each SLOSH model run. Variability in the radius of maximum wind, which is also known to have a significant impact on storm surge, is also considered. The result is a map of cumulative storm surge probabilities that indicate the overall chances that the indicated storm surge will occur at each location on the map during the period between hour 0 (the beginning of the forecast) and 3 days (72 hours) after the beginning of the forecast.

It is important for users to realize that probabilities that may seem relatively small may still be quite significant. The probabilities might indicate there is a chance that a damaging or even an extreme event could occur at your location. As a storm gets closer to land, relatively small probabilities may warrant making preparations to protect lives and property. Users are urged to consider the potentially immense cost (in terms of lives, property, etc.) of not preparing for an extreme event, even if the chances at an individual point are only perhaps 1 in 20 (5%) or 1 in 10 (10%) that the event will occur.

A full description of other NWS Tropical Cyclone Weather Services Program Products is provided in NWSI 10-601, which is available on the Internet at the following URL:


The NHC will produce a set of updated storm surge probability graphics whenever a hurricane watch or hurricane warning is in effect for any portion of the Gulf or Atlantic coasts of the continental United States. These graphics will take approximately 30 minutes (perhaps more) to update on the NHC website following the issuance of the NHC tropical cyclone advisories at 5:00 AM EDT, 11:00 AM EDT, 5:00 PM EDT, and 11:00 PM EDT (or 4:00 AM EST, 10:00 AM EST, 4:00 PM EST, and 10:00 PM EST).

These graphics can be found here when advisories are created for an active storm.


P-SURGE Heights Example Example 1. Static example of the Probabilistic Storm Surge Heights output. Note that the actual product is interactive with pan and zoom capability.

P-SURGE Exceedance Example Example 2. Static example of the Probabilistic Storm Surge Exceedance output. Note that the actual product is interactive with pan and zoom capability.

Quick Navigation Links:
Tropical Cyclone Forecasts  -  Tropical Marine Forecasts  -  Data Archive
Outreach  -  Prepare  -  About Cyclones  -  About NHC  -  Contact Us

NOAA/ National Weather Service
National Centers for Environmental Prediction
National Hurricane Center
11691 SW 17th Street
Miami, Florida 33165 USA
Information Quality
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities
Page last modified: Monday, 19-May-2014 15:59:15 UTC