Center. In their study it was found that the standard rule for steering tropical cyclones (the movement of the storm from about 10° to 20° to the right of the current flowing over the top of the core) was only reliable prior to  recurvature  and  that  storms  after  recurvature frequently move to the left of the steering current. Operating on the premise that the motion of the tropical storm is not governed by forces acting at any one level, their study encompasses three levels, the 700-,500-, and 300- hPa levels. They found that the 700- and 500-mb charts were about equal in forecasting hurricane motion. In the final analysis, the 700-hPa level was selected and combined  with  the  previous  12-hour  motion  of  the storm. From their study, a slightly better verification of predicted tracks of hurricanes resulted rather than from use of sea level data (statistical method) or the 500-mb chart alone. The Basic Grid in Steering Tropical Systems The basic grid is essentially the same as that used in the  500-hPa  method  except  that  gradients  were computed at intervals of 2.5° latitude instead of 5°. The previous  12-hour  motion  was  also  incorporated  into  the forecast. This method was tested on 23 forecasts during the  1958  hurricane  season.  The  average  error  was  95 nautical miles for the 24-hour forecast and ranged from 15 nautical miles to 170 nautical miles. A  further  explanation  of  this  method  and  its procedure for application may be found in the Bulletin of  the  American  Meteorological  Society,  Vol. 41, No. 2, February  1960. TROPICAL  CYCLONE  WARNINGS Tropical cyclone warnings are issued to protect not only Department of Defense assets but also those of allied nations. Tropical Cyclone Warnings of the Atlantic Tropical  cyclone  warnings  are  issued  to  operating forces of the Atlantic Ocean, the Gulf of Mexico, and the   Caribbean   region   by   NAVLANTMETOCCEN Norfolk, Va. Warnings for the southern hemisphere are provided  as  required. NAVLANTMETOCCEN primarily   uses   the   National   Hurricane   Center’s interagency  and  public  advisories  as  guidance. Hurricane, tropical storm, and tropical depression warnings are issued four times daily at 0300 UTC, 0900 UTC, 1500 UTC, and 2100 UTC. They are listed under the MAANOP heading WHNT__ KNGU. The blank space is for the numerical sequence of the warning. Special advisories and warnings are issued in the event of significant changes in intensity or movement. Daily tropical weather summaries are issued at 1800 UTC  from  01  June  through  30  November  for  the subtropical Atlantic (south of 30°N), the Caribbean, and the Gulf of Mexico. Daily tropical weather summaries are listed under the MANOP heading ABCA KNGU. Tropical  cyclone  warning  messages  are  transmitted via  AUTODIN  and  the  Fleet  Multichannel  Broadcast every 6 hours for storms in the Northern Hemisphere. Tropical Cyclone Warnings of the Pacific Tropical  cyclone  warnings  are  issued  to  operating forces of the Pacific Ocean (west of 180° longitude), Philippine  Sea,  South  China  Sea,  Bay  of  Bengal,  and Indian  Ocean  in  both  the  Northern  and  Southern Hemispheres by the Joint Typhoon Warning Center (JTWC),  Guam. Tropical  cyclone  warnings  are  issued  to  operating forces of the Pacific Ocean east of 180° longitude by NAVPACMETOCCEN   Pearl   Harbor,   Hawaii. Warnings for the Southern Hemisphere are provided as required. NAVPACMETOCCEN primarily uses the National Hurricane Center’s interagency and public advisories  as  guidance. Typhoon,  tropical  storm,  tropical  depression,  and tropical cyclone warnings are issued four times daily at 0300 UTC, 0900 UTC, 1500 UTC, and 2100 UTC. The warnings from the JTWC are listed under the MANOP heading  WTPN  PGTW  and  the  warnings  from NAVPACMETOCCEN  Pearl  Harbor  are  listed  under the MANOP heading WTPZ PHNL. The blank space is for the numerical sequence of the warning. Special advisories and warnings are issued in the event of significant changes in intensity or movement. Tropical  cyclone  warning  messages  are  transmitted via  AUTODIN  and  the  Fleet  Multichannel  Broadcast every 6 hours for storms in the Northern Hemisphere. NAVMETOCCOM  centers  monitor  Southern Hemisphere  tropical  cyclones  in  their  individual  AORs. Because  of  the  limited  data  and  weather  satellite coverage of the Southern Hemisphere, warnings are issued  by  AUTODIN  and  Fleet  Multichannel  Broadcast only at 12- and 24-hour intervals and may contain less specific   information   than   Northern   Hemisphere warnings. 11-10