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 are characterized by the origin of the disturbance and the wind speed.

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