Skip Navigation Links weather.gov   
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
   Audio/Podcasts
   About Advisories
Marine Forecasts
   Atlantic & E Pacific
   Gridded Marine
   About Marine
Tools & Data
   Satellite | Radar
   Analysis Tools
   Aircraft Recon
   GIS Datasets
   Data Archive
Development
   Experimental
   Research
   Forecast Accuracy
Outreach & Education
   Prepare
   Storm Surge
   About Cyclones
   Cyclone Names
   Wind Scale
   Most Extreme
   Forecast Models
   Breakpoints
   Resources
   Glossary | Acronyms
   Frequent Questions
Our Organization
   About NHC
   Mission & Vision
   Staff | Q&A
   Visitors | Virtual Tour
   Library Branch
   NCEP | Newsletter
Contact Us
   Comments
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
FirstGov.gov is the U.S. Government's official Web portal to all Federal, state and local government Web resources and services.
 
 

Service Change Notice


NOUS41 KWBC 281600
PNSWSH           
 
Service Change Notice 14-11
National Weather Service Headquarters Washington DC
1040 AM EST Fri Feb 28 2014
 
To:      Subscribers:
         -Family of Services 
         -NOAA Weather Wire Service
         -Emergency Manager Weather Information Network
         -NOAAPORT
         Other NWS partners and NWS employees
 
From:    Mark Tew
         Chief, Marine and Coastal Weather Services Branch 
 
Subject: Changes to text Tropical Cyclone Wind Speed Probability
         Product Effective May 15, 2014  
 
Effective May 15,2014 the following changes will take place with
the text Tropical Cyclone Wind Speed Probability (PWS) product
issued by the National Hurricane Center and Central Pacific
Hurricane Center: 
 
1. Removal of Maximum Wind Speed (Intensity) Probability Table
(Table I) This table gives the likelihood that a tropical
cyclone will be at any of several different intensity
categories (e.g., depression, storm, category 1 hurricane,
etc.) at fixed points in time (e.g., 12 hours, 24 hours, 36
hours, etc.). These probabilities are estimated by creating
a large number of potential track and intensity scenarios
based on the latest official forecast and a climatological
error distribution. NHC has learned that many users consult
this table to estimate the chances that a tropical cyclone
will make landfall at one or more of the various intensity
categories. Unfortunately, the current methodology provides
a highly misleading estimate of landfall intensity. 
 
The problem can be seen by considering a storm that is
forecast to be just offshore at 72 hours. A sizable fraction
of the potential scenarios have already encountered land by
that time, and for these over-land scenarios the expected
intensity at 72 hours will be much lower than what would be
expected for a storm that was still over water and about to
make landfall. Even though the table accurately assesses
what the intensity is likely to be at 72 hours, it grossly
underestimates the likely intensity for when the storm comes
ashore.
 
The table was originally intended to help users assess the
risk of different categories of storms at particular times,
and for storms well away from land the product serves that
function well; however, because of the high likelihood of
misuse for land-threatening storms, and the consequences of
that misuse for the general public, NHC and CPHC are
discontinuing this table until a better procedure to
estimate intensity risk can be developed.
     
2. Wind Speed Probability Table for Specific Locations (Table
II) - The name of one of the parameters in this table will
change from Individual Probability (IP) to Onset Probability (OP). 
This parameter is defined as the probability of the event
beginning during an individual time period (e.g., between
24 and 36 hours).  The name Onset probability better highlights
the difference between this parameter, which provides information
on when the event is likely to begin, and the Cumulative
Probability, which describes the likelihood that the event
will occur at all.
 
The PWS can be found online at:
 
Atlantic and east Pacific basin:
 
http://www.nhc.noaa.gov
 
Central Pacific basin:
 
http://www.prh.noaa.gov/cphc
 
The WMO headers and AWIPS Identifiers (AI) for the PWS are:
 
Basin                WMO Header              AI
Atlantic             FONT/11-15/ KNHC        MIAPWSAT/1-5/
East Pacific         FOPZ/11-15/ KNHC        MIAPWSEP/1-5/
Central Pacific      FOPA/11-15/ PHFO        HFOPWSCP/1-5/
 
An example of the changes can be found at:
 
www.nhc.noaa.gov/news/20140228_hsu_windProbsTextChanges.php
 
In addition, NWS will no longer provide the stand-alone Intensity
(Maximum Wind Speed) Probability graphic. This graphic contained
the identical information to Table I of the PWS product, which is
being discontinued.
 
If you have comments or questions please contact:
 
    John Kuhn
    National Weather Service
    Marine and Coastal Weather Services Branch
    Silver Spring, Maryland 20910
    Email: John.F.Kuhn@noaa.gov
    Phone: 301-713-1677 extension 121
 
National Public Information Statements are online at:
 
    http://www.weather.gov/om/notif.htm
 
$$


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
nhcwebmaster@noaa.gov
Disclaimer
Credits
Information Quality
Glossary
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities
Page last modified: Friday, 28-Feb-2014 19:33:01 UTC