CHAPTER  10 SPECIAL OBSERVATIONS AND FORECASTS In  this  chapter  we  will  discuss  a  few  special observations and forecasts generated to ensure the safety   of   U.S.   Navy   ships,   aircraft,   shore-based commands, and personnel. The first topic to be discussed will be those products disseminated   by   theater   METOCCENS   and METOCFACS.    The  warnings  and  advisories  presented are further described in the  U.S.  Navy  Oceanographic and   Meteorological   Support   System   Manual, NAVMETOCCOMINST  3140.1,  as  well  as  local command  standard  operating  procedures. SIGNIFICANT  WEATHER, SEA ADVISORIES, AND WARNINGS LEARNING  OBJECTIVES:   Describe   the content of various warnings, advisories, and forecasts  issued  by  NAVMETOCCOM  and USMC units. Advisories and warnings of potentially destructive weather  are  routinely  issued  by  NAVMETOCCOM  and USMC  weather  activities.  These  services  are  provided in  direct  support  of  Navy  requirements  outlined  in OPNAVINST  3140.24,  Warnings  and  Conditions  of Readiness  Concerning  Hazardous  or  Destructive Weather Phenomena. Conditions of readiness are set by   the   local   area   commander   or   designated representative. NAVMETOCCOM does not set these conditions. These advisories and warnings are based on forecast wind velocities and significant wave heights. . Wind velocity.  Because of its variability, wind velocity is usually expressed in a 10-knot range in speed and 45-degree range indirection. Wind speed forecasts are not averages over the forecast period, but are rather the  sustained  wind  speeds  (2-minute  average)  expected over the period and area of the forecast. Amplifying remarks, such as backing, veering, shifting, and so forth, are   added   to   wind   advisories   and   warnings,   as appropriate. . Significant wave height. Significant  wave  height is defined as the average of the highest one-third of all waves  observed  in  the  sea,  which  includes  both short-period   and   long-period   waves.   Short-period waves (seas) are normally generated by local winds, while  long-period  waves  (swells)  are  generated  by winds at a distance. WIND  WARNINGS Wind warnings are characterized by the origin of the disturbance and the wind speed. Extra-tropical  Systems The following warnings pertain to extra-tropical systems, or tropical systems other than closed cyclonic circulations. l  Small  Craft  Warnings.  Small  craft  warnings are  issued  in  harbors,  inland  waters,  and  coastal OPAREAS, as well as other coastal inshore regions prescribed by the local area commander. The lower limit of the sustained wind speed used to set this warning varies  by  region  and  is  defined  by  the  local  area commander.  The  local  NAVMETOCCOM  or  USMC aviation  weather  activity  can  provide  further information. . Gale Warnings. Area(s) experiencing sustained wind speeds of 35 knots or higher will be bounded and a gale warning issued. . Storm Warnings. Area(s)  experiencing  sustained wind speeds of 50 knots or higher will be bounded and a storm warning issued. . Wind Warnings. Wind warnings for the Northern Hemisphere are automatically disseminated via the Fleet  Multichannel  Broadcast  or  Automatic  Digital Network  (AUTODIN).  Automatic  dissemination  of warnings in the Southern Hemisphere are limited to specifically  defined  areas  designated  by  fleet commanders  due  to  limited  naval  operations  and sparsity  of  observations.  Wind  warnings  are  normally issued every 12 hours. 10-1