OFFSHORE CURRENTS.— These currents are
found outside the surf zone (both tidal and nontidal).
. Tidal currents are predominant near entrances to
bays and sounds, channels, between islands, or between
islands and the mainland.
. Tidal currents usually reverse direction on a
periodic basis (every 6 to 12 hours) and can reach speeds
up to several knots.
RIP CURRENTS.— These currents result from
waves piling water up against the coast. They flow
along the coast until they are deflected seaward by
bottom irregularities or until they meet another current.
. Flow can reach speeds as high as 12 kts, but
usually attain speeds of 2 to 4 kts. Prevents most landing
craft from making any headway ashore.
. The head (leading edge) of the current is often
discolored by silt in suspension.
l If the beach is irregular, they will flow along the
beach for a short distance and then flow out to sea.
l They are easily identified by aircraft, as they
create a turbid flume offshore.
SHORE CURRENTS.— The following discussion
deals with the formation and characteristics of shore
currents.
. Generated by waves breaking at an angle to the
beach.
l Littoral or longshore currents flow parallel to the
beach inside the breakers.
. Speeds increase with increasing breaker height,
with increasing angle of the breaker with the beach, and
with steeper slopes.
. Speeds decrease with increasing wave period.
. In areas where longshore/littoral currents are
common, sandbars are usually present.
. Longshore/littoral currents must be considered in
selecting a beach or landing site. A littoral current can
cause a landing craft to broach.
Further discussion of beach topography, beach
composition, beach surveys, breakers, and offshore
sealswells may be found in the technical manual,
CWOSM, Part 1, TM 04-92.
For further discussion of AMW operations refer to
the technical manual, CWOSM, Part 1, TM 04-92
and Joint Surf Manual, COMNAVSURFPAC/
COMNAVSURFLANT Instruction 3840.1. The last
topic of discussion in this chapter will be the briefing of
METOC services available from OA divisions.
BRIEFING OF AVAILABLE METOC
SERVICES
LEARNING OBJECTIVES: Brief OTCs and
interested personnel on METOC conditions, as
well as communications.
Previous discussions in this chapter have dealt with
various briefs that OA division personnel are required
to present on a routine basis. METOC support was
standardized recently to better support afloat units
Navywide.
This plan includes Meteorology/
Oceanography (OPTASK METOC) and several tactical
support summaries. This standardized format will now
be contained in ANNEX H to numbered fleet basic
OPORDs.
The standardization to ANNEX H to the numbered
fleet OPORDs and information previously presented in
this chapter and technical manual, CWOSM, Part 1,
should ensure all METOC briefs, regardless of
respective fleets, will outline all necessary elements of
benefit to OTCs.
SUMMARY
In this chapter we discussed various METOC briefs
conducted by Aerographer personnel. Among those
presented were tropical cyclone disaster planning,
tropical cyclone evasion/sortie, storm surge, MIW,
AMW, and those used in fleet coordinated
exercises/operations. It should be understood that these
are just a few of the many METOC briefs that
Aerographers may present.
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