Effective May 15, the National Hurricane Center will implement the following changes to its text and graphical products.
Changes:
1) Product headers will now indicate the correct status of a system on its final advisory. NHC stops writing advisories on tropical cyclones when they lose tropical characteristics or when they dissipate. In the past, product headers on final advisories have caused confusion – for example, when the header reads “TROPICAL STORM FRAN ADVISORY…”, but the body of the advisory indicates that the system is no longer a tropical cyclone. Beginning this year, when NHC writes the final advisory on a system, the product headers will now indicate the actual status of the system (e.g., REMNANTS OF FRAN ADVISORY…”). The complete list of cyclone types that may appear in the header block is:
Tropical Depression Tropical Storm Hurricane
Subtropical Depression
Subtropical Storm Post-Tropical Cyclone Remnants of
An example and complete list of affected products is found at:
http://www.nhc.noaa.gov/2011_types.shtml
2) The Tropical Cyclone Discussion (TCD) will include forecast intensity in miles- per-hour (mph). The TCD that is issued with each advisory package contains a table that includes the forecast valid times, forecast cyclone locations and intensities. Previously, the table displayed forecast intensity in knots (KT). Beginning May 15, the table will also include the intensity forecast in miles-per- hour (MPH). See the example below:
FORECAST POSITIONS AND MAX WINDS
INIT 28/0900Z 15.7N 50.1W 50 KT 60 MPH
12H 28/1800Z 16.0N 52.7W 60 KT 70 MPH
24H 29/0600Z 16.5N 55.7W 65 KT 75 MPH
36H 29/1800Z 17.2N 58.3W 75 KT 85 MPH
48H 30/0600Z 18.2N 60.5W 85 KT 100 MPH
72H 31/0600Z 20.8N 64.2W 100 KT 115 MPH
96H 01/0600Z 24.5N 67.5W 110 KT 125 MPH
120H 02/0600Z 29.5N 69.5W 100 KT 115 MPH
3) The pronunciation guide for storm names as been updated to include phonetic pronunciations of all Atlantic and Eastern North Pacific storm names. The list of names and pronunciation guide is found on the NHC website at:
Atlantic:
http://www.nhc.noaa.gov/pdf/aboutnames_pronounce_atlc.pdf
Eastern North Pacific:
http://www.nhc.noaa.gov/pdf/aboutnames_pronounce_epac.pdf
4) The abbreviation for kilometers per hour in the NHC products will change from
KM/HR to KM/H.
5) Storm Surge Exceedance products will become operational in 2011. The exceedance graphics show the storm surge height, in feet above normal tide level, which has a specific probability of being exceeded in the next 3 days. The available probability thresholds range from 10 to 90 percent, at 10 percent intervals. The products are available on the NHC website when a hurricane watch or warning is in effect for the United States.
Information on NHC Storm Surge products is found at:
http://www.nhc.noaa.gov/ssurge/ssurge_products.shtml
Other information items of interest for 2011:
1) A reminder that the lead times of tropical cyclone watches and warnings were increased in 2010. The definitions of tropical storm and hurricane watches and warnings are as follows:
Tropical Storm Watch: An announcement that tropical storm conditions (sustained winds of 39 to 73 mph) are possible within the specified coastal area within 48 hours.
Tropical Storm Warning: An announcement that tropical storm conditions (sustained winds of 39 to 73 mph) are expected within the specified coastal area within 36 hours.
Hurricane Watch: An announcement that hurricane conditions (sustained winds of 74 mph or higher) are possible somewhere within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds.
Hurricane Warning: An announcement that hurricane conditions (sustained winds of 74 mph or higher) are expected somewhere within the specified coastal area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds.
2) The size of the tropical cyclone forecast cone will be adjusted. The cone represents the probable track of the center of a tropical cyclone, and is formed by enclosing the area swept out by a set of imaginary circles placed along the forecast track (at 12, 24, 36 hours, etc.). The size of each circle is set so that two-thirds of historical official forecast errors over the previous five years fall within the circle. The circle radii defining the cones in 2011 for the Atlantic and
eastern North Pacific basins are given in the table below:
Forecast Period (hours)
Circle radius Atlantic Basin (nautical miles)
Circle radius
Eastern North Pacific Basin
(nautical miles)
12 36 33
24 59 59
36 79 79
48 98 98
72 144 134
96 190 187
120 239 230
3) The National Hurricane Center now has a Facebook page. The “NOAA NWS National Hurricane Center” page will provide updates about the NHC outreach and education campaign and other items that might be of interest to the public throughout the year. During the hurricane season, the site will contain links to
the NHC web site (hurricanes.gov) highlighting active tropical weather. The
NHC Facebook page is found at:
http://www.facebook.com/US.NOAA.NationalHurricaneCenter.gov
Experimental Products: (Note that the timeliness and accuracy of these products cannot be guaranteed)
1) Audio podcast RSS/XML feed for top-of-the-hour briefings when the media pool is activated:
http://www.nhc.noaa.gov/audio/index.shtml
(The media pool is typically activated when a hurricane watch is issued for any portion of the U.S. contiguous coastline.)
2) Live video/audio feed of top-of-the-hour hurricane briefings when the media pool is activated:
http://www.emergency.info/nhc/
3) Various GIS products:
http://www.nhc.noaa.gov/gis/
On the Web:
National Hurricane Center http://www.hurricanes.gov
National Hurricane Center Product Description Document-A User’s Guide to Hurricane
Products:
http://www.nhc.noaa.gov/pdf/NHC_Product_Description.pdf
Graphical Tropical Weather Outlook:
http://www.nhc.noaa.gov/aboutnhcgraphics.shtml#GTWO
Saffir Simpson Hurricane Wind Scale:
http://www.nhc.noaa.gov/aboutsshs.shtml
Definition of NHC Track Forecast Cone:
http://www.nhc.noaa.gov/aboutcone.shtml
National Hurricane Center Facebook page:
http://www.facebook.com/US.NOAA.NationalHurricaneCenter.gov
Contact: NHC Public Affairs, nhc.public.affairs@noaa.gov
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