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Tropical Cyclone Advisory Format Changes

Effective May 15 response to the needs of NWS customers the Tropical Prediction Center/National Hurricane Center /NHC/ and the Central Pacific Hurricane Center /CPHC/ will extend tropical cyclone forecast products from 3 days (72 hours) to 5 days (120 hours). Increasing tropical cyclone forecasts to 5 days changes the following products.

Tropical Cyclone Forecast/Advisory

Product WMO Heading AWIPS ID
Atlantic WTNT<21-25> KNHC TCMAT<1-5>
East Pacific WTPZ<21-25> KNHC TCMEP<1-5>
Central Pacific WTPA<21-25> PHFO TCMCP<1-5>

Tropical Cyclone Discussion

Product WMO Heading AWIPS ID
Atlantic WTNT<41-45> KNHC TCDAT<1-5>
East Pacific WTPZ<41-45> KNHC TCDEP<1-5>
Central Pacific WTPA<41-45> PHFO TCDCP<1-5>

Note...there are no changes to WMO headings or AWIPS identifiers and no actions are required for continued receipt of products from NHC and CPHC. However...the issuing office line identifier in the Mass News Disseminator Block for the TCM and TCD will change to ensure these products conform to NWS Instruction (NWSI) 10-1701...entitled Text Formats and Codes.

The Issuing Office Line Identifier for NHC products will read


The Issuing Office Line Identifier for CPHC products will read


Other changes to the Forecast/Advisory (TCM)

  1. 48 and 72 hour OUTLOOK lines become FORECAST lines.
  2. 96 and 120 hour OUTLOOK lines added with FORECAST positions and forecast maximum sustained wind speeds (MAX WIND) reported to the nearest 5 knots.
  3. EXTENDED OUTLOOK CAUTIONARY NOTE modified to include the 96 and 120 hour track and wind speed average errors.
  4. REQUEST FOR 3 HOURLY SHIP REPORTS moved just prior to the NEXT ADVISORY line
  5. Tropical Cyclone code identifier in header changed to 4-digit year (format is BBNNYYYY where BB is basin (AL, EP, CP) NN is tropical cyclone number and YYYY is the year).

Other changes for the Discussion (TCD)

  1. 96 and 120 hour FORECAST POSITIONS and MAX WINDS (Maximum Sustained Wind Speeds, nearest 5 knots) added to the FORECAST TABLE
  2. Removed "S" from knots (KTS) in the FORECAST TABLE

Examples of the new formats (ASCII text files)

Users of tropical cyclone forecast products are encouraged to not focus on just the forecast position of a storm center...but to consider the uncertainty associated with storm track well as the potentially large geographic area that may be impacted by tropical cyclone conditions. Average errors noted in the TCM products are based on the past two years of experimental forecasts.

If you have any questions...please contact

Mr. Scott Kiser
National Weather Service
Marine and Coastal Services Branch
1325 East West Hwy Room 13126
Silver Spring, MD 20910
Phone: 301-713-1677 Extension 121