Table of Contents Previous Chapter 5 Marine Products
This chapter describes marine products that will be supported by AFPS for Stage 2 AWIPS. These product descriptions are largely based on current products. Significant changes in the marine program are expected before Stage 2.

At this time we do not have complete information on how marine products in Stage 2 will differ from current (1992) marine products. Minor changes, where known, are noted following the phrase "in Stage 2." The source of the information is the National Weather Service Operations Manual, chapters D-51 (oceanic) and D-52 (Great Lakes), unless otherwise specified.

Table12 summarizes the product parameters for the marine products.

Table 12 - Marine Product Parameters 
------------------------------------------------------------------------------------------
Parameter                      Coastal   Great     Great      Local     Alaska    Offshore  
                               Marine    Lakes     Lakes      Marine    Coastal   Forecast  
                               Forecast  Forecast  Nearshore  Forecast  Marine              
                                (CWF)     (GLF)     Marine              Forecast            
                                                   Forecast                                 
                                                   (NSH)                                    
------------------------------------------------------------------------------------------
Synopsis                       X         X         X                    X         X         
Advisory/Watch/Warning         X         X         X          X         X         X         
Headlines                                                                                   
Wind Direction                 X         X         X          X         X         X         
Wind Speed                     X         X         X          X         X         X         
Wave Height                    X         X         X          X         X         X         
Swell Height                   X                              X         X         X         
Swell Direction                X                              X         X         X         
Significant Weather            X         X         X          X         X         X         
Sky Cover                                          X                                        
Precipitation Intensity        X         X         X          X         X         X         
Probability of Precipitation             X         X          X         X         X         
Visibility                     X         X         X          X         X         X         
Obstructions to Vision         X         X         X          X         X         X         
Coastal/Lakeshore Flooding     X                   X          X         X                   
Heavy Surf                     X                                        X                   
Beach Erosion                  X                                        X                   
Tidal Anomalies                X                              X         X                   
Superstructure Icing or Icing  X         X                              X         X         
Sea Ice                        X                                        X         X         
Temperature (Air)                                                       X         X         
Other Forecast Elements                                       X                             
Additional Information         X                   X                                        
Coastal Forecast Summary                                                X                   
Table                                                                                       
Outlook                        X                                        X         X         
------------------------------------------------------------------------------------------

5.1 Coastal Marine Forecast (CWF)

5.1.1 Description

The Coastal Marine Forecast (also known as the Coastal Waters Forecast) is a free-formatted product containing forecast elements and derived parameters. It is issued four times per day, and covers three periods (36 hours) from issuance time.

Coastal marine forecasts are designed to serve the needs of the widest variety of maritime activities. Coastal water traffic ranges from numerous small and weather-sensitive craft, many of which do not venture far from land, to oceangoing vessels. Another important activity is offshore oil and gas production which operates drilling ships and fixed platforms.

In Stage 2, CWF areas will be aligned with public zones, and will extend to 100 nautical miles offshore, corresponding to the effective seaward range of coastal NEXRAD network coverage. The present Offshore forecast will be replaced by these enlarged coastal forecasts, and by modified High Seas forecasts, except in Alaska.

An example of the CWF is shown in Figure5.

Figure 5 - Example Coastal Marine Forecast

5.1.2 Product Parameters for the CWF

5.1.2.1 Synopsis

The synopsis provides a verbal picture of the weather patterns producing the conditions described in the forecast. The description identifies major weather systems and their strength, trend, movement and location at the end of the forecast period.

Major weather features include pressure systems (highs, lows), fronts, troughs, and ridges. Locations of low pressure centers are described by distance in nautical miles and by compass direction to 8 points (e.g., NORTH, NORTHEAST) from a known landmark. Locations of high pressure centers are described in terms of general area proximity (e.g., SOUTHEASTERN U.S.; OFF THE MID-ATLANTIC COAST). Locations of fronts, troughs and ridges are described in terms of general area proximity or by compass direction and distance offshore. Movement of major weather systems is expressed by direction and speed in knots. Strength and trend of pressure centers is expressed qualitatively (e.g., STRONG, WEAK; DEEPENING, WEAKENING). Central pressures in millibars are given rarely.

Tropical cyclone information consisting of an appropriate identification of the tropical cyclone, its location, movement, and time (local) derived from the latest official advisory, and the statement SEE LATEST ADVISORY appears within the synopsis if appropriate. The location of the cyclone is given by direction, using a 16 point compass, and by distance in nautical miles, from a known landmark.(1)

5.1.2.2 Advisory / Watch / Warning Headlines

Appropriate advisories, watches, and warnings are headlined for small craft, gale, or storm-force winds, tropical cyclone conditions, coastal flooding, heavy surf, or winter storm conditions.

5.1.2.3 Wind Direction

The wind direction at or near the surface is described to 8 points of the compass, e.g., NORTHEAST. The term VARIABLE or the suffix -ERLY may be used at 15 knots or less in areas where topography is a factor.

5.1.2.4 Wind Speed

Speed at or near the surface is described in knots to the nearest 5 knots. Wind below 10 knots may be described as 10 KNOTS OR LESS.

If a range of wind speeds is given, it is not usually more than 5 knots for speeds up to 25 knots and 10 knots for higher speeds. A wider range is given under certain extratropical and tropical conditions.

Variations in strength are described (e.g., GUSTS, VARIABLE, DIMINISHING). Gusts are described if significant, as for example, WITH FREQUENT HIGHER GUSTS, or GUSTING TO 55 KTS. Variations with time or location are described when significant. Qualitative terms may be used, such as LIGHT.

If winds are expected to increase to an advisory category beyond 12 hours or a warning category beyond 24 hours after forecast issuance, statements such as SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED (TIME) or GALE (STORM) FORCE WINDS ARE EXPECTED (TIME) are headlined.

5.1.2.5 Wave Height

Seas are waves made by local wind and are described in terms of height to the nearest foot, where height has a special definition as "significant wave height," the average height of the one-third highest of a record of waves. This is the value reported by NOAA data buoys and observers at sea. Variations with location are described. Time variations such as BUILDING TO 15FT BY TONIGHT are described. Qualitative terms such as HEAVY, ROUGH, and MODERATE may be included.

5.1.2.6 Swell Height

Swell is generated by remote storms, and is described in terms of height in feet in the same sense as above.

5.1.2.7 Swell Direction

Swell direction is indicated by eight compass points, if possible. Period in seconds is rarely included.

5.1.2.8 Significant Weather

Significant weather is that weather which is expected to have a significant effect on marine operations. Emphasis is placed on thunderstorm activity, since this may produce locally hazardous winds and seas.

The types of weather reported in the CWF are listed in Table13. Thunderstorm descriptors include FREQUENT LIGHTNING, HEAVY DOWNPOUR, GUSTS, HAIL, CHANCE OF THUNDERSTORMS, CHANCE OF SEVERE THUNDERSTORMS, DAMAGING WINDS, and LARGE HAIL.

Table 13 - Precipitation Types for Marine Forecasts 
----------------------------------------------------------------------------------------------
Type              Description                                                                   
----------------------------------------------------------------------------------------------
Thunderstorm      A local storm produced by a cumulonimbus cloud. It is always accompa          
                  nied by lightning and thunder, often with strong gusts of wind, heavy         
                  rain, and sometimes with hail.                                                
Rain              Steady fall of several hours of liquid precipitation. Drops are larger than   
                  0.02 inch or small drops which are widely separated.                          
Rain Showers      Short duration of intermittent rainfall.                                      
Sprinkles         Short duration of very light intermittent rainfall.                           
Drizzle           Fairly uniform liquid precipitation composed exclusively of fine drops        
                  very close together.                                                          
Freezing Rain     Rain which freezes on contact with the ground or other exposed areas.         
Freezing Drizzle  Drizzle which freezes on contact with the ground or other exposed areas.      
Hail              Precipitation of small balls or other pieces of ice falling separately or     
                  frozen together in irregular lumps.                                           
Sleet             Frozen raindrops which, like hail, usually bounce when hitting a hard         
                  surface. Does not "stick" to surfaces.                                        
Snow              Steady fall of several hours of frozen snow crystals, typically in the        
                  shaped of six-pointed stars.                                                  
Snow Showers      Short duration of intermittent snowfall. Some accumulation possible.          
Flurries          Short duration of very light snow showers.                                    
Snow Squalls      Intense snowfall, with gusty winds. Accumulations may be significant.         
Ice Crystals      A fall of unbranched ice crystals in the form of needles, columns, or         
                  plates.                                                                       
                                                                                                
----------------------------------------------------------------------------------------------

5.1.2.9 Precipitation Intensity

Precipitation intensity is classified into categories. Only significant intensities are forecast: HEAVY and VERY HEAVY.

5.1.2.10 Probability of Precipitation

Probability of precipitation is given categorically. Valid probabilities are CHANCE, OCCASIONAL, LIKELY, and no mention, denoting definite.

5.1.2.11 Visibility

Visibility is expressed in miles. In the absence of data or reliable techniques, the mention of obstructions to vision is sufficient.

5.1.2.12 Obstructions to Vision

The obstructions to vision that may be mentioned in a coastal waters forecast are listed in Table14. Combinations of obstructions are allowed.

Table 14 - Obstructions to Vision for Marine Forecasts 
------------------------------------------------------------------------------------
Obstruction to Vision  Description                                                    
------------------------------------------------------------------------------------
Fog                    Visible aggregate of minute water particles (droplets)         
                       which are based at the Earth's surface.                        
Haze                   A suspension in the air of extremely small, dry particles      
                       invisible to the naked eye and sufficiently numerous to        
                       give the air an opalescent appearance.                         
Smoke                  A suspension in the air of small particles produced by         
                       combustion.                                                    
Blowing Spray          Water droplets torn by the wind from a body of water           
                       and raised in such quantities as to reduce the visibility at   
                       eye level to 6 miles or less.                                  
                                                                                      
------------------------------------------------------------------------------------

5.1.2.13 Coastal/Lakeshore Flooding

Information on coastal or lakeshore flooding is included when significant. Variations with time or position are included as needed.

5.1.2.14 Heavy Surf

Information on heavy surf is included when significant.

5.1.2.15 Beach Erosion

Information on beach erosion is included when significant.

5.1.2.16 Tidal Anomalies

Information on tidal anomalies is included when significant. Tidal anomalies are given in feet above a customary level, such as ABOVE NORMAL. Variations with time or position are included as needed.

5.1.2.17 Superstructure Icing

Superstructure icing indicates the likelihood of ice accretion on exposed surfaces. Its forecast is based on wind, air and sea temperatures, and wave action. The valid categories for superstructure icing are listed in Table15.

Table 15 - Superstructure Icing Categories 
-------------------------------------------
Category    Ice Accretion Rate               
-------------------------------------------
Light       Up to 0.3 inches per hour        
Moderate    0.3 to 0.8 inches per hour       
Heavy       0.8 to 2.0 inches per hour       
Very Heavy  2.0 inches and greater per hour  
                                             
-------------------------------------------

5.1.2.18 Sea Ice

General ice information is included in forecasts for mid-Atlantic and New England coastal areas if conditions are expected to have an adverse effect on marine traffic. This is rare.

5.1.2.19 Additional Information

Additional information can be included at the end of the forecast with regional approval. Normally this would be a statement of water temperature for recreational users such as WATER TEMPERATURE AT THE MOUTH OF THE BAY IS 64 DEGREES.

5.1.2.20 Outlook

An outlook through 5 days is appended to the forecast. It simply mentions Gale or Storm Force Winds for the period or portions thereof and, if applicable, forecast location of tropical cyclones extracted from the latest official advisory. If winds are forecast to be below gale force, a statement such as GALE FORECE OR STRONGER WINDS NOT EXPECTED is included.

5.2 Great Lakes Forecast (GLF)

5.2.1 Description

The Great Lakes Forecast (also known as the Open Lake Forecast or the Lake Forecast) is a free-formatted product containing forecast elements and derived parameters. It is issued four times per day by Ann Arbor (Lake Huron), Buffalo (Lake Ontario), Chicago (Lake Superior and Michigan), and Cleveland (Lake Erie), and covers three periods (about 36 hours) from issuance time. The forecast is valid beyond five nautical miles from shore. This product presently (1992) includes the MAFOR, a coded 24 hour forecast.

In Stage 2 the forecasts will be issued by five WFO's (those above plus Marquette - Lake Superior). Cleveland will continue regional focus and coordination.

An example of the GLF is shown in Figure5.

Figure 6 - Great Lakes Forecast

5.2.2 Product Parameters for the Great Lakes Forecasts

5.2.2.1 Synopsis

Significant weather systems affecting the Great Lakes region are described. The synopsis is similar to that described in Section 5.1.2.1, Synopsis, on page27. The synopsis is issued only by WSFO Cleveland.

5.2.2.2 Watch / Warning Headline

Gale and Storm warnings are headlined in the product if appropriate.

5.2.2.3 Wind Direction

Wind direction is forecast to eight points of the compass. The term VARIABLE or the suffix -ERLY may be used for winds at 15 knots or less.

5.2.2.4 Wind Speed

Wind speeds in the open lake forecasts are intended for use primarily by large vessels with anemometer heights 60 to 100 feet above the water line. Speeds are described in 5- or 10- knot ranges, rounded to the nearest 5-knot increment, up to 25 knots. Thereafter, a single wind speed is used such as NORTH GALES TO 35 KNOTS. If winds are expected to be in a warning category in the third period (beyond 24 hours) a term such as 40 KNOT GALES or STORM FORCE WINDS 50 KNOTS or A GALE WARNING MAY BE ISSUED BY (TIME) is added to imply later warnings.

Note that this procedure may be changed to that described in Section 5.1.2.4, Wind Speed, on page28.

5.2.2.5 Wave Height

Significant wave height (the average trough to crest distance of a record of the one third highest waves) is forecast. A range of values indicates the height to the nearest foot at the end of the fetch (downwind end of the lake - that area where the greatest significant waves are expected). The range is intended to show the uncertainty of precise values in the downwind area. It is not intended to indicate a range of heights over the entire lake. The mariner should infer the heights in other areas based on his position and the wind direction. Swells are not described.

5.2.2.6 Significant weather

Significant weather is that weather which is expected to have a significant effect on marine operations. Emphasis is placed on thunderstorm activity since this may produce locally hazardous winds and seas.

The types of weather reported in the GLF are the same as for the CWF, listed in Section 5.1.2.8, Significant Weather, on page29.

5.2.2.7 Precipitation Intensity

Precipitation intensity is classified into categories. Only significant intensities are forecast: HEAVY and VERY HEAVY.

5.2.2.8 Probability of Precipitation

Probability of precipitation is given categorically. Valid probabilities are CHANCE, OCCASIONAL, LIKELY, and no mention, denoting definite.

5.2.2.9 Visibility

Visibility is forecast in miles. In the absence of data or reliable techniques, the mention of obstructions to vision is sufficient.

5.2.2.10 Obstructions to Vision

The obstructions to vision that may be mentioned in a Great Lakes Forecast are listed in Table14, Obstructions to Vision for Marine Forecasts, on page30. Combinations of obstructions are allowed.

5.2.2.11 Superstructure Icing

Superstructure icing indicates the likelihood of ice accretion on exposed surfaces. Its forecast is based on wind, air and sea temperatures, and wave action. Refer to Table15 on page31 for icing categories.

Note that lake ice is not included in the GLF.

5.3 Great Lakes Nearshore Marine Forecast (NSH)

5.3.1 Description

The Nearshore Forecast is a free-formatted product containing forecast elements and derived parameters. It is issued four times per day by twelve offices on the Great Lakes, and covers three 12-hour periods (36 hours) from issuance time. The forecasts are issued on a seasonal basis, spring through fall. The forecast is valid within 5 nautical miles of shore. Nearshore forecasts are concise and include only predominant conditions.

In Stage 2 the Nearshore forecast will still extend to 5 nautical miles offshore, and forecast areas will be aligned with public zones.

An example of the NSH is shown in Figure5 on page27.

Figure 7 - Great Lakes Nearshore Forecast

5.3.2 Product Parameters for the Nearshore Forecast

5.3.2.1 Synopsis

Significant weather systems affecting the forecast area are described. The synopsis is similar to that described in Section 5.1.2.1, Synopsis, on page27. The synopsis is issued only by WSFO Cleveland.

5.3.2.2 Advisory/Watch/Warning Headline

Small craft advisories, gale warnings, and storm warnings are headlined in the product if appropriate.

5.3.2.3 Wind Direction

Wind direction is forecast to eight points of the compass. The term VARIABLE or the suffix -ERLY may be used for winds at 15 knots or less.

5.3.2.4 Wind Speed

Wind speed in the nearshore forecast is intended for use primarily by small vessels and applies within a few feet of the surface of the lake. Speeds are described in 5- or 10- knot ranges, rounded to the nearest 5-knot increment, up to 25 knots. Thereafter, a single wind speed is used as NORTH WINDS 30 KNOTS. If winds are expected to be in an advisory category in the second period (beyond 12 hours) or a warning category in the third period (beyond 24 hours) a term such as 40 KNOT GALES or STORM FORCE WINDS TO 50 KNOTS or A SMALL CRAFT ADVISORY MAY BE ISSUED BY (TIME) is added to imply a later advisory or warning. Note that this procedure may be changed to that described in Section 5.1.2.4, Wind Speed, on page28.

5.3.2.5 Wave Height

Significant wave height (the average trough to crest distance of a record of the one third highest waves) is specified. A range of values is used to indicate the height to the nearest foot. Swells are not described.

5.3.2.6 Significant Weather

Significant weather is that weather which is expected to have a significant effect on marine operations. Emphasis is placed on thunderstorm activity since this may produce locally hazardous winds and seas.

The types of weather reported in the NSH are the same as for the CWF and GLF, listed in Section 5.1.2.8, Significant Weather, on page29.

5.3.2.7 Sky Cover

Since much of the NSH's audience is recreational, terms such as SUNNY and PARTLY CLOUDY are helpful for planning activities.

5.3.2.8 Precipitation Intensity

As for the CWF and GLF, precipitation intensity is classified into categories. Only significant intensities are forecast: HEAVY and VERY HEAVY.

5.3.2.9 Probability of Precipitation

Probability of precipitation is given categorically. Valid probabilities are CHANCE, OCCASIONAL, LIKELY, and no mention, meaning definite.

5.3.2.10 Visibility

Visibility is forecast in miles. In the absence of data or reliable measurement techniques, the mention of obstructions to vision is sufficient.

5.3.2.11 Obstructions to Vision

The obstructions to vision that may be mentioned in a Nearshore Forecast are listed in Table14, Obstructions to Vision for Marine Forecasts, on page30. Combinations of obstructions are allowed.

5.3.2.12 Coastal/Lakeshore Flooding

Information on coastal or lakeshore flooding is included when significant. Variations with time or position are included as needed.

5.3.2.13 Additional information

Additional information can be included at the end of the forecast with regional approval. The only actual use of this option noted in recent forecasts is a statement of water temperature nearshore, presumably for recreational users, such as THE WATER TEMPERATURE OFF CLEVELAND IS 64 DEGREES.

5.4 Local Marine Forecast(2)

5.4.1 Description

Certain areas in the United States have a heavy mixture of large commercial ships and smaller commercial and recreational vessels. To enhance the safety of mariners, NWS regions may authorize individual offices to issue Local Marine Forecasts for such areas. These forecasts may be appended to the coastal waters forecast for the adjoining marine area, may be appended to the associated public forecast, or may stand alone.

Local Marine Forecasts include wind, sea state, and significant weather as described earlier in this chapter. However, regions may allow individual element forecasts for special cases such as the Columbia River Bar. Emphasis is placed on conditions where poor visibility or severe local storms may directly affect mariners. Tide information is included if significant.

In Stage 2, the Local Marine Forecast will presumably be a stand-alone product. An example is shown in Figure8.

Figure 8 - Local Marine Forecast Example

5.4.2 Product Parameters for the Local Marine Forecast

5.4.2.1 Advisory / Watch / Warning Headlines

Appropriate advisories, watches, and warnings are headlined for small craft, gale, or storm force winds, coastal flooding, heavy surf, or winter storm conditions.

5.4.2.2 Wind Direction

Surface wind direction (nominally 10 meters above sea level) is forecast to eight points of the compass. The term VARIABLE or the suffix -ERLY may be used for winds at 15 knots or less.

5.4.2.3 Wind Speed

Wind speed in the local marine forecast is intended for use by both small and large vessels and applies to within a few feet of the surface. Speeds are described in 5- or 10- knot ranges, rounded to the nearest 5-knot increment, up to 25 knots. Thereafter, a single wind speed is used as NORTH WINDS 30 KNOTS.

If winds are expected to increase to an advisory category beyond 12 hours or a warning category beyond 24 hours after forecast issuance, statements such as SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED (TIME) or GALE (STORM) FORCE WINDS ARE EXPECTED (TIME) are headlined.

5.4.2.4 Sea State

Wave height and swell height and direction are included, in the same fashion as described earlier in this chapter. See Section 5.1.2, Product Parameters for the CWF, on page27.

5.4.2.5 Significant Weather

Significant weather is that weather which is expected to have a significant effect on marine operations. Emphasis is placed on thunderstorm activity since this may produce locally hazardous winds and seas.

As for the other marine forecasts, the types of weather are as listed in Section 5.1.2.8, Significant Weather, on page29.

5.4.2.6 Precipitation Intensity

Precipitation intensity is classified into categories. Only significant intensities are forecast: HEAVY and VERY HEAVY.

5.4.2.7 Probability of Precipitation

Probability of precipitation is given categorically. Valid probabilities are CHANCE, OCCASIONAL, LIKELY, and no mention, denoting definite.

5.4.2.8 Visibility

Visibility is forecast in miles. In the absence of data or reliable techniques, the mention of obstructions to vision is sufficient.

5.4.2.9 Obstructions to Vision

The obstructions to vision that may be mentioned in a local marine forecast are listed in Table14, Obstructions to Vision for Marine Forecasts, on page30. Combinations of obstructions are allowed.

5.4.2.10 Coastal/Lakeshore Flooding

Information on coastal or lakeshore flooding is included when significant.

5.4.2.11 Tidal Anomalies

Information on tidal anomalies is included when significant.

5.4.2.12 Other Forecast Elements

Other forecast elements may be placed within the local marine forecast per regional approval.

5.5 Alaska Coastal Marine Forecast(3)

5.5.1 Description

The Alaskan Coastal Marine Forecast is identical to other Coastal Waters Forecasts, with the exceptions described here. Currently there are fourteen coastal forecast areas controlled by WSFO Juneau, WSFO Anchorage, and WSFO Fairbanks. The forecasts are issued twice a day. The forecast period is for 26 hours plus a 24 hour outlook. Unlike other Coastal Marine Forecasts that are formatted in terms of discrete 12 hour forecast periods, each containing all pertinent weather elements, the Alaska Coastal Marine Forecast is formatted according to weather elements where each element (e.g., winds) is described for the 24 hour period.

In Stage 2, the Coastal Marine Forecast areas will be extended to 100 nautical miles offshore, but no other boundary or landmark changes will be made.

An example of the Alaska Coastal Marine Forecast is shown in Figure10.

Figure 9 - Alaska Coastal Marine Forecast

5.5.2 Product Parameters

5.5.2.1 Synopsis

See Section 5.1.2.1, Synopsis, on page27 for a description of the synopsis parameter.

5.5.2.2 Advisory / Watch / Warning Headlines

Appropriate advisories, watches, and warnings are headlined for small craft, gale, or storm force winds, coastal flooding, heavy surf, or winter storm conditions.

5.5.2.3 Wind Direction (10 meter)

Wind direction at 10 meters is described to 8 points of the compass, e.g., NORTHEAST. The term VARIABLE or the suffix -ERLY may be used at 15 knots or less in areas where topography is a factor.

5.5.2.4 Wind Speed (10 meter)

Speed at the 10 meter height is described in knots to the nearest knot but is normally rounded to the nearest 5 knots. Ranges of wind speed are not given.

Variations in strength are described (e.g., GUSTS, VARIABLE, DIMINISHING). Gusts are described if significant, as for example, WITH FREQUENT HIGHER GUSTS, or GUSTING TO 55 KT. Variations with time or location are described when significant. Qualitative terms may be used, such as LIGHT.

If winds are expected to increase to an advisory category beyond 12 hours or a warning category beyond 24 hours after forecast issuance, statements such as SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED (TIME) or GALE (STORM) FORCE WINDS ARE EXPECTED (TIME) are headlined.

5.5.2.5 Sea State

Wave height and swell height and direction are included, as in other products. Descriptions of these parameters appear in Section 5.1.2, Product Parameters for the CWF, on page27.

5.5.2.6 Significant Weather

Significant weather is that weather which is expected to have a significant effect on marine operations. Emphasis is placed on thunderstorm activity since this may produce locally hazardous winds and seas. Terms listed in Table13, Precipitation Types for Marine Forecasts, on page29, are permitted, with the exception of FLURRIES, SNOW SQUALLS, ICE CRYSTALS, and HAIL.

Modifiers of these terms are allowable if they describe intensity or probability of occurrence, e.g., heavy, dense, chance, or occasional. However, terms like "periods of," "areas of," etc. are not used. They tend to obscure the required detail in the forecast. The intent is for the forecast to be as specific as possible, requiring a minimum of interpretation by the marine community.

5.5.2.7 Precipitation Intensity

Precipitation intensity is classified into categories. Only significant intensities are forecast: HEAVY and VERY HEAVY.

5.5.2.8 Probability of Precipitation

Probability of precipitation is given categorically. Valid probabilities are CHANCE, OCCASIONAL, LIKELY, and no mention, indicating definite.

5.5.2.9 Visibility

Visibility is forecast in miles. In the absence of data or reliable techniques, the mention of obstructions to vision is sufficient.

5.5.2.10 Obstructions to Vision

Only FOG and HAZE are allowed in this forecast. See Table14, Obstructions to Vision for Marine Forecasts, on page30 for a description of these phenomena.

5.5.2.11 Coastal Flooding

Information on coastal flooding is included when significant. Variations with time or position are included as needed.

5.5.2.12 Heavy Surf, Beach Erosion

Information on heavy surf and/or beach erosion is included when significant.

5.5.2.13 Tidal Anomalies

Significant tidal anomalies are included. Tidal anomalies are given in feet above a customary level, such as ABOVE NORMAL. Variations with time or position are included as needed.

5.5.2.14 Icing

Superstructure icing due to freezing spray is one of the most hazardous phenomena that the Alaskan mariner must contend with. Whenever available data on wind, air and sea temperature, and wave activity suggest the likelihood of superstructure icing, the Coastal Marine Forecast includes a statement on icing potential. Because ice accumulation rates are ultimately dependent upon individual ship characteristics and operating conditions, icing potential is stated using specific terms. These terms are described in Table16.

Table 16 - Alaska Coastal Waters Icing Categories 
---------------------------------
Category              Description  
---------------------------------
Freezing Spray        ???          
Heavy Freezing Spray  ???          
                                   
---------------------------------

5.5.2.15 Sea Ice

A description of potential sea ice and limits of sea ice is included in the product if expected to be hazardous to marine activities.

5.5.2.16 Temperature

Forecast air temperature is included in the product when expected to be below 32 degrees Fahrenheit.

5.5.2.17 Coastal Forecast Summary Table

A 12- and 24- hour forecast summary table follows selected Alaskan coastal marine forecasts. This is a summary of the coastal marine forecasts and is prepared by each WSFO for its areas of responsibility. The summary includes the forecaster's best estimate of the predominant conditions that will occur within the forecast area.

Included in the table are winds (direction to 8 compass points and speed in knots), sea (height in feet), weather (abbreviated weather term), icing, and warning (e.g., SMCR for Small Craft Advisory, GALE, BRSK for Brisk Wind Advisory, and STRM), for each of the coastal forecast areas for the 12- and 24- hour valid times.

5.5.2.18 Outlook

A 5-day outlook of the expected major storm track(s) affecting Alaskan marine waters is appended to the Alaska Coastal Marine Forecast. The text consists of a short statement of the expected storm track during the next five days and the relative intensity of storms. No specific reference to individual storm locations or intensities is made. The message is typically limited to 75 words or less.

5.6 Offshore Forecast(4)

5.6.1 Description

The Offshore forecast is issued twice a day at 1100 and 2300 UTC by the Anchorage, Juneau, and Fairbanks(5) WSFOs. Honolulu issues the Offshore forecast for the area near Hawaii. This section describes the Alaska Offshore Forecast; the Hawaiian Offshore Forecast is expected to be similar.

The content and format of the Offshore Forecast in Alaska is the same as the Coastal Waters Forecast in Alaska(6), except a 3 to 5 day extended marine forecast section is appended to each Offshore Forecast as outlined in WSOM Chapter D-51. The Offshore Forecast for each area contains:

An Extended Forecast for the combined areas is appended to the above forecasts, covering days 3 through 5, including an indication of gale or storm winds.

Currently there are two offshore forecast areas controlled by WSFO Anchorage (Gulf of Alaska, Bering Sea), two for Fairbanks(7) (Chukchi Sea, Beaufort Sea), and one for Honolulu(8).

An example of the Offshore Forecast is shown in Figure10.

Figure 10 - Alaska Offshore Forecast

5.6.2 Product Parameters

5.6.2.1 Synopsis

See Section 5.1.2.1, Synopsis, on page27 for a description of the synopsis parameter. The major differences is that central pressures are given in millibars and locations are in terms of map coordinates (latitude, longitude). Significant features are described with reference made to forecast parameters.

5.6.2.2 Advisory / Watch / Warning Headlines

Appropriate advisories, watches, and warnings are headlined for gale- or storm-force winds, severe local storms, tropical cyclone conditions, coastal flooding, heavy surf, or winter storm conditions. Small craft advisories are not included in the Offshore Forecast.

5.6.2.3 Wind Direction (Sustained)

The wind direction at or near the surface is described to 8 points of the compass, e.g., NORTHEAST. The term VARIABLE or the suffix -ERLY may be used at 15 knots or less in areas where topography is a factor.

Wind can be defined relative to a meteorological feature, such as a front, low center, or high center, to better convey the forecast picture.

5.6.2.4 Wind Speed (Sustained)

Speed at or near the surface is described in knots to the nearest knot but is normally rounded to the nearest 5 knots. Ranges of wind speed are not given.

Variations in strength are described (e.g., GUSTS, VARIABLE, DIMINISHING). Gusts are more hazardous at sea than on land and should be described if present, as for example, WITH FREQUENT HIGHER GUSTS, or GUSTING TO 55 KTS. Variations with time or location are described when significant. Qualitative terms may be used, such as LIGHT.

Wind can be defined relative to a meteorological feature, such as a front, low center, or high center, to better convey the forecast picture.

5.6.2.5 Sea State

Wave height and swell height and direction are included, in the same fashion as described earlier in this chapter. See Section 5.1.2, Product Parameters for the CWF, on page27.

Each of these elements can be defined relative to a meteorological feature, such as a front, low center, or high center, to better convey the forecast picture.

5.6.2.6 Significant Weather

Significant weather is that weather which is expected to have a significant effect on marine operations. See Section 5.5.2.6, Significant Weather, on page39 for more information.

5.6.2.7 Precipitation Intensity

Precipitation intensity is classified into categories. Only significant intensities are forecast: HEAVY and VERY HEAVY.

5.6.2.8 Probability of Precipitation

Probability of precipitation is given categorically. Valid probabilities are CHANCE, OCCASIONAL, LIKELY, and no mention, indicating definite.

5.6.2.9 Visibility

Visibility is forecast in miles. In the absence of data or reliable techniques, the mention of obstructions to vision is sufficient.

5.6.2.10 Obstructions to Vision

The obstructions to vision that may be mentioned in a coastal waters forecast are listed in Table14 on page30. Combinations of obstructions are allowed.

5.6.2.11 Icing

Superstructure icing due to freezing spray is one of the most hazardous phenomena that the Alaskan mariner must contend with. See Section 5.5.2.14, Icing, on page40 for more detail.

5.6.2.12 Sea Ice

A description of potential sea ice and limits of sea ice is included in the product if it is expected to pose a hazard to marine activities.

5.6.2.13 Temperature

Forecast air temperature is included in the product when it is expected to be below freezing.

5.6.2.14 Outlook

A 5-day outlook of the expected major storm track(s) affecting Alaskan marine waters is appended to the Offshore Forecast. The text consists of a short statement of the expected storm track during the next five days and the relative intensity of storms. No specific reference to individual storm locations or intensities is made. The message typically is limited to 75 words or less.


Footnotes

(1)
Operations Manual Letter 4-91.
(2)
Information gleaned from NWS Operations Manual Letter 10-91, September, 1991.
(3)
Information obtained from the Alaska Region Regional Operations Manual Letter (ROML) A-13-87, November 20, 1987, and ROML A-02-88, June 27, 1988.
(4)
Information from Regional Operations Manual Letter A-02-91 dated March 11, 1991.
(5)
WSFO Fairbanks issues the Alaska Offshore Forecast only under special conditions.
(6)
Note that the High Seas Forecast issued by the Meteorological Operations Division of NMC includes the same waters. The High Seas and Offshore forecasts have different meteorological scales and user perspectives but must be consistent and coordinated.
(7)
These are issued only upon request.
(8)
The area consists of a one thousand mile radius from Honolulu.
 
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