National Weather Service (NWS) Hurricane Centers provide tropical cyclone advisories to NAVEASTOCEANCEN Norfolk, Virginia, and NAVWESTOCEANCEN Pearl Harbor, Hawaii, for the Atlantic Ocean and Pacific Ocean (east of 180 longitude) respectively. These centers take the advisories and formulate warnings for their respective areas of responsibility. Since there is no NWS Hurricane Center in the western Pacific, the NAVOCEANCOMCEN/Joint Typhoon Warning Center at Guam has the responsibility for issuing warnings there and in the Indian Ocean.

All tropical cyclones are numbered and/or named. Tropical depressions are numbered, and once they intensify to tropical storms they are named. This is standard operating procedure at the COMNAVOCEANCOM activities listed above. However, the numbering system is not standard. The procedures for numbering the military advisories and warnings differ. These procedures should be checked when operating in each Centers area of responsibility. Tropical cyclone advisories and warnings contain the following information:

. Current position (latitude/longitude) of cyclone

. Method of determining position (satellite, radar, observation, etc.)

. Position accuracy assessment (excellent, good, fair, poor)

. Direction and speed of the cyclone

. Diameter of eye (if known)

. Maximum sustained winds and gusts

. Extent of gale-, storm-, and hurricane-force winds

. Extent of high seas (12 feet or greater)

. 12-, 14, 48, and 72-hour forecast positions verifying at synoptic times

Because of the highly erratic courses taken by many of these cyclones and their destructiveness, advisories and warnings are issued at least every 6 hours. An example of a tropical cyclone warning is shown in figure 9-3-11.

Most weather offices maintain track charts on each tropical cyclone. You simply plot the current position as taken from each warning issued. Some offices use acetate-covered charts. The current position is plotted using one color grease pencil, and the forecast positions are plotted on the acetate in another color grease pencil. When the last warning issued is received, the track is transferred in ink to the base chart for historical purposes. Track charts are an excellent briefing tool.