Click for next page ( 30


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 29
Findings and Recommendations The seven findings discussed below were distilled from the responses to the questionnaire, workshop presentations, open discussions, and work- ing group reports. They represent a synthesis and consensus statement by the committee of topics that need to be addressed to improve the pro- duction and dissemination of marine forecasts in the support of safety of life and property and the enhancement of our economic use of the sea. They are prioritized by the order in which they should be implemented. Although a considerable effort was made by the committee to quantify the cost, schedule, and potential benefit that could be realized by the implementation of these recommendations, these could not be estimated with sufficient accuracy for inclusion here. Many of the recommendations can be implemented incrementally, with benefit increasing with both time and cost. The first five findings (better management, hurricane forecasting, more synoptic data, better space/time resolution, and improved broadcast services) are primarily concerned with the maintenance and incremen- tal improvement of existing products and services. The remaining three (operational oceanographic satellite, forecast internal ocean weather, and episodic waves/explosive cyclogenesis) are necessary to move into a new generation of improved products and services. FINDING 1: IMPROVED COORDINATION IS NEEDED All too frequently the committee was unable to identify the per- son or agency clearly and singly responsible for operation of the obse~v- ing/forecasting system and end user support. Throughout the workshop and 29

OCR for page 29
30 in subsequent discussions by the committee, the need for improved coor- dination among the various agencies became evident. Nine executive level departments and nearly 40 federal agencies deal with the oceans. There is, in addition, a private sector industry of approximately $100 million annually providing forecasts and tailored products to various users. Marine Data Collection The committee found abundant evidence of inadequate coordination in the observation and collection of marine data. One of the working groups estimated that 25 to 30 percent of the observations collected at sea are not transmitted to shore, and a significant percentage of those observations are not used in the analysis and forecast process. Many reasons for this were related to transmission and quality control and to the lack of any responsible individual or agency. Data Assimilation and Modeling Data are processed and numerical models are run by both the National Weather Service and National Ocean Service components of NOAA and by the Fleet Numerical Oceanography Center of the U.S. Navy. Although the forecast products of the centers are generally available to each other, the Navy cannot depend on non-Navy sources that might disappear during times of increased tension, and NOAA must develop its own products in case the Navy classifies its products. At the present time, both agencies share unclassified data, but classified data are restricted to military use. Product Dissemination Nowcast and forecast data are disseminated by NOAA, Navy, Coast Guard, news media, and private services. Forecasts for the same place from two or more of these sources may not agree because they are based on different analyses and prepared by different experts. There are many offshore regions that are now covered only by Navy facsimile broadcasts. When the Navy shifts to encrypted digital transmission of its environmental information, most ships in these regions will be left with no source of information. Private Sector Forecasts There has been considerable debate during the past 5 years over "privatization" of forecast services. Private forecasters are concerned that the government issues, at no cost, products that they could sell to individual

OCR for page 29
31 customers. The committee believes that the growth of the "value-added" private sector by a factor of 10 over the past decade demonstrates that there is a reasonable balance between government and private sector products. - 0 ~ r -- - RECOMMENDATION: Improve Management. Improved coordina- tion of the national ocean forecasting program is of such critical importance that a review of policy should be undertaken by the administrator of NOAA and the oceanographer of the Navy. Among the specific issues of concern to the committee are designation of a national policy and a lead agency for an operational oceanographic satellite system; designation of a national policy and a lead agency for nowcasting and forecasting internal ocean weather; maintenance and improvement of the services provided to the civil sector; and maintenance of the free exchange of data and information. These issues are discussed in detail in the following findings and recom- mendations. This recommendation has the highest priority because it Is necessary for the successful implementation of those that follow. FINDING 2: HURRICANE FORECASTING IS ADEQUATE AND SOURCES OF DATA AND FORECASTING TECHNIQUES SHOULD BE MAINTAINED The hurricane (known as a typhoon in the Western Pacific Ocean and a cyclone in the Indian Ocean) is the single most feared and potentially destructive weather event at sea. These intense storms, with wind speeds that can reach well above 100 miles per hour, are well-known hazards to all forms of marine and coastal commerce. There is ample record of the loss of property and life caused by the hurricane and its winds, waves, and resultant coastal flooding. With modern satellite systems, numerical weather models, dedicated hurricane reconnaissance aircraft, and modern communications, the threat of the unannounced onslaught of these storms has been greatly reduced, especially in and around the continental United States. Accordingly, the National Weather Service has dedicated a priority effort to tracking and forecasting hurricanes from the National Hurricane Center (NHC) located in Miami, Florida. This is matched in the Pacific by a combined effort of the Navy and Air Force to man the Joint Typhoon Warning Center located in Guam and the Central Pacific Hurricane Warning Center (CPHC) in Honolulu. The NHC and the CPHC rely on conventional meteorological reports from shipping and weather centers around the globe, dedicated aircraft flights into the centers of known storms that threaten the United States, and, for detection and tracking, available satellite and

OCR for page 29
32 radar data. This focus has been highly effective in providing nowcasts and forecasts of hurricane formation and behavior. It was the general consensus of those providing user inputs to the committee, and of the committee itself, that present efforts are adequate to the user need.lAll parties emphasized, however, that present capabilities should not be degraded in any manner. There was general consensus that while current satellite observations are essential, the present state of sensor development and the lack of assured redundancy on orbit continue to make dedicated aircraft reconnaissance of active storm centers the only way to define central pressures, to ascertain accurate wind velocities, and often to localize the storm center when a well-defined eye is not observable from space due to clouds or darkness. The following comments extracted from the reports of the working groups shed additional light on this situation. Forecasting by the National Weather Service and user response to such forecasts have been successful in minimizing loss of life due to hurricane occurrence in U.S. coastal regions. User groups are aware of the uncertainties of hurricane forecasting and generally accept the burdens of false alarm evacuation. The potential for improvements notwithstanding, the present forecasting of tropical storms lay NWS is considered satisfactory by the fishing and shipping fleets. There seems to be low prospect for technical improvement in forecasting hurricane tracks until all-weather satellite remote sensing is developed and made operational. Federal agencies and local authorities or users should place emphasis on improving evacuation and decision making. NWS needs to assure that real- time or near-real-time, hurricane weather data gathering and distribution are maintained or even improved, such as by the installation of a coastal radar [referring to a Doppler radar or NEXRAD in the Gulf Coast region, offshore]. There is general satisfaction with the NOAA [hurricane] products in terms of how they are handled and how people respond. There is a feeling the NWS in their hurricane watch and warning business provides what is needed. There is great concern that there be no degradation in the quality and nature of what is produced. The real-time data from aircraft flights, satellites, and buoys are being used, and there is an urgent recommendation not to cut any of these inputs. The NWS forecasting of hurricanes and user response has been judged a success in guarding public safeW. It is important to maintain or even increase public confidence in hurricane evacuation management. FINDING 3: MORE SYNOPTIC DATA ARE NEEDED Typically in ocean nowcasting or forecasting, the field to be forecast 1 It is important to note that the committee did not have the benefit of the views of local disaster preparedness agencies.

OCR for page 29
33 is underdefined. Increasingly, the amount of accurate and timely data to initialize the analysis model significantly increases the accuracy of the resulting forecast. Obtaining high-quality data on internal ocean fields and the atmosphere over the oceans and repeating this on a regular basis is the starting point for all marine forecasting. The oceans, which comprise some 70 percent of the earth's surface, are vast and remote. There are few reporting points except for islands and vessels at sea. The NWS and the Navy have extensive programs to get data reported from ships at sea. 1b be useful in the model runs that are the basis of forecast guidance, the observations must reach the modeling center in a timely manner. They must arrive, sometimes from far-flung locations, in time to be quality checked for errors and entered into the model. The value of satellites that can sample the entire earth's surface one or more times per day is immediately obvious. Satellites, even those with sensors greatly limited by cloud cover, can provide more data about the ocean's surface and a better areal coverage than that available from vessels steaming a limited number of great circle routes between major ports of call. Operational Oceanographic Satellite The nation now has no plans to field a suite of sensors tailored to measure, in an operational mode, the ocean variables deemed most critical to ocean forecasting. These sensors would include the altimeter for measuring ocean topography from which currents can be determined, the scatterometer with a primary role of measuring the wind speed and direction over the ocean and thus allowing for better estimation of wave parameters, the scanning microwave sensor to measure sea surface temperature and the presence or absence of ice and for providing another estimate of wind and waves, and the low-frequency microwave radiometer to provide a cloud-independent look at sea-surface temperature. The potential to revolutionize ocean forecasting may be realized if these fields are measured simultaneously from an orbit optimized for synoptic forecasting, and the data are transmitted to primary operational ocean modeling centers. NASA is continuing a program to demonstrate the utility of several of these sensors. These include a high-quality altimeter with precision orbital tracking, a scatterometer, and an ocean color instrument to be flown in cooperation with industry. Flights of these instruments will be in partner- ship with programs of other countries to ensure a launch vehicle. NASA is also entering into a cooperative venture to obtain synthetic aperture radar data for the study of ice in polar regions. It was made clear to the committee that the NASA effort was not a program designed for provision of a near-real-time data stream to operational analysis and forecast centers. At best, the operational agencies with need for ocean remotely sensed data

OCR for page 29
34 will continue to rely on the NOAA weather satellites, the DOD weather satellite, and whatever quasi-operational data can be gleaned from other programs, such as the extended oceanographic mission of GEOSAT and the SEAWIFS program proposed by EOSAT. While certainly beneficial and endorsed by the committee, these measures do not have the overall impact of a set of dedicated operational oceanographic sensors in orbit linked by rapid communications to the major analysis centers of NOAA and the Navy. Lost Data Opportunities While an operational oceanographic satellite is necessary for improved ocean forecasting, ship reports are equally necessary because only they provide data on subsurface ocean conditions. There Is a surprising inef- ficiency in the collection of oceanic and atmospheric data from various marine platforms. The committee found that only about 50 percent of potentially available marine data reports are being operationally utilized in nowcasts and forecasts. The remaining reports are either not sent, lost in transmission, arrive too late for the model run, or contain too many errors to be useful. The provider and user representatives and the members of the committee felt that a concerted effort should be made to solve this problem. The following comments were made by the working groups. Ibe present functioning of the Vessel Observation Service (VOS) is plagued by numerous problems related to quality control, timeliness of reporting, commu- nications processing, and shipboard procedures. [For example, the committee learned that on U.S. flag ships it is common not to report observations at night because transmitting at night requires special overtime pay for radio operators.] The assessment of the disappointing electiveness of the VOS program strongly suggests that the program suffers from a lack of nurturing. The following deficiencies were found: significant loss of data within complex communication system, significant delay on delivery of data to forecasters, insufficient provision for providing unused data to forecasters, antiquated and slow communications, and insufficient use of reliable, quality controlled satellite communica- tions. RECOMMENDATION: Operational Oceanographic Satellite System. A national program for an operational oceanographic satellite system should be established. RECOMMENDATION: Improve Data Collection. NOAA should make a strong effort to increase the efficient voluntary reporting of timely marine observations and to increase the number of vessels providing these important data. Automation of shipboard observation systems and the use

OCR for page 29
35 of satellite communication links are vital to increasing the quantity and quality of marine data. FINDING 4: IMPROVEMENTS ARE NEEDED IN RESOLUTION IN SPACE AND TIME ANI) FORECAST HORIZON Many users, especially those whose use of the ocean is generally within 50 miles of shore, found that the present system of forecasting and forecast dissemination provided information that did not meet their needs. This was based on the spatial area covered by the forecast, the spatial resolution of the forecast, the time interval between forecast updates or modifications, and the forecast time horizon, that is, the future period covered by the forecast such as the 24-hour or 12-hour outlook This situation was exacer- bated for operations that were critically weather dependent. An example of this type of operation would be dredging or the operation of small pleasure craft. Shipping A major concern for vessel operators is the nature of extratropical storms over the high seas. Often, forecasts are for vast ocean regions, especially when large air masses dominate a region such as the Eastern North Atlantic. The vessel operators desire more specific location data on frontal systems, especially the horizontal depth of the frontal feature, the speed with which the front is progressing, and, when possible, the exact position of the center of low pressure. This information is desired on a fairly frequent interval to permit evasive action to be taken during transit. A specific area of concern to the shipping community is the landfall region for approach to ports. Here the ship operator is interested not only in pressure systems and the associated wind and wave fields, but also visibility and, in high latitudes, ice. Topography also has an impact on wind direction and wind speed both in benign and storm situations. In general, smaller area forecasts would be beneficial to the shipping community in terms of minimizing time lost, vessel and cargo damage, and the potential loss of human life due to weather. A review of documents recording marine losses provided to the com- mittee by several insurance underwriters indicates that weather losses are a steady source of claims each year. While specific conclusions cannot be drawn from those documents without additional data and extensive analysis, the trend of a constant worldwide impact on shipping is clear. It should be noted that weather is a prominent factor listed in claims where total loss of the vessel is involved.

OCR for page 29
36 Oil and Gas Exploration and Production Offshore oil and gas exploration and production operations often need small area and short time window forecasts. They need specific projections of sea state and wind conditions when conducting critical operations. For such highly specific operations as the evacuation by boat or helicopter of offshore oil fields that lie in the path of a severe storm, or the tow and placement of platform structures, highly site- and time-specific weather forecasts can significantly reduce the risks to both men and materials and ultimately translate into large cost benefits if done on time and without damage. A reasonably significant body of private forecasters and private forecasting service companies are key assistants to the major energy extrac- tion companies in support of such decision making. Fishing and Recreational Boating This community of relatively small boat owners and operators is ex- tremely sensitive to the local area nearshore forecast. Users commonly complain that the forecast areas are often much too large to be meaningful to an operator whose sailing radius from a port may be less than 20 miles. Forecasts that cover 100 miles or more of coastline often do not contain sufficient local detail. Local conditions may vary a great deal from the wide area forecast. General comments obtained by the committee through its survey and workshop request more detail on local wind and wave con- ditions, the time and speed of frontal passage, and expected conditions. Small changes in wind or wave forecast may have a real impact on this class of operator. For example, a wind speed forecast of 15 to 25 knots does not help operators who will be heading home at 15 knots, in difficult at 20 knots, and a potential search and rescue case waiting to happen at 25 knots. These users would like additional forecasts at both ends of the time scale, more frequent forecast updates or nowcasts for local areas to support actual operations, and a better 24-hour outlook to support plan- ning. For example, many recreational boats plan to stay in port based on a marine forecast tailored to a 10(\ to 200-mile coastal area. The forecast that causes numbers of recreational boaters to choose to stay in port can mean significant dollar losses to a local community, especially if a season for a particular fishery is short in duration. Overall, more frequent and more site-specific forecasts would be of extreme benefit to the fishing and recreational boating communities. The benefits would be measured in in- creased safety, improved utilization of resources, and a potential financial plus for the region.

OCR for page 29
37 Dredging and Ocean Engineering These operations are often extremely sensitive to very local nearshore marine conditions. Dredging operations generally rely on machinery and barges that are not self-propelled and cannot avoid the onset of unexpected adverse weather. Commonly these platforms and equipment are sensitive to swell conditions in excess of 3 to 6 feet and can be carried from their moorings and set aground by strong wind and wave combinations. Knowledge of near-term weather is needed to permit adequate preparation without constant costly downtime. A typical dredging operation takes place within a 5 nautical mile radius of some given location. This highlights the site specificity of the forecasts desired. Ocean engineering activities that include such common coastal developments as construction of piers, jetties, and seawalls to laying of subsurface piping and the building of bridges all can be extremely dependent on weather for personnel safety and the prevention of equipment loss. Included under ocean engineering from this perspective is the cleanup of pollution events with the use of booms and small boats. All of the operations discussed above could be aided by more site-and time-specific forecasts, especially in the coastal region. Additional detailed discussion may be found in the reports of Working Groups 1 and 2 (see Appendixes E and F). RECOMMENDATION: Improve Resolution. NOAA can and should increase the usefulness of its products, where supported by present analyses and forecasts by increasing the resolution in space and time, extending the time horizon of forecasts, and increasing the frequency of issue. Future product improvements should emphasize increased resolution and meeting user needs. FINDING 5: IMPROVED DISSEMINATION SYSTEMS AND LINKAGE TO NAVY MARINE FACSIMILE BROADCAST ARE NEEDED The dissemination of marine weather information and the potential loss of the Navy marine facsimile broadcast was a common point of discussion by almost all vessel operators. As technology and federal budgets rapidly change, there is a strong feeling among several user communities notably fisheries and marine transportation- that federal agencies will be setting policy and adopting new communications systems with little interaction with the users. NOAA Weather Radio The primary means of disseminating marine weather information to

OCR for page 29
38 the general public, the recreational boating and fishing communities, and the commercial fishing fleet is either by commercial broadcast (radio and television) or the NOAA Weather Radio system. Many concerns about the existing NOAA radio system were driven in part by the larger number of boats using the coastal zone and the size and speed of today's boats that often can operate far offshore and remain out overnight. The concerns can be broken into three general areas: broadcast range, broadcast timing, and broadcast content. There was nearly unanimous consensus that the range of the present system should be expanded to accommodate vessels, both commercial and private, out to a range of at least 50 miles. Much discussion arose about centering weather information for particular regions at a fixed time every hour. For example, the marine forecast for the area from river mouth x to headland y would always fall at 27 minutes after the hour. Also, significant numbers of users wanted more information on specific weather features not now included in the broadcast. For example: more information on fronts and frontal passage; elimination of divergent forecasts for the same area when there is overlap by two stations; more information on weather to the west, that is to say, weather coming into the forecast area; and more frequent updates during storms. The NAVTEX System The NAVTEX system is an evolving, international, direct printing information dissemination system that will be mandatory by August 1993 for cargo vessels over 300 tons and for all passenger vessels on international voyages. Its proposed range under the provisions of the Safebr of Life at Sea Convention (SOLAS) is nominally out to 200 miles. NAVI~X will early marine safety and hydrographic information. It will also provide offshore weather products for the ocean region that is nominally 60 to 200 miles offshore.iUser community concerns about NAVTEX center on two Issues: 1. Will there be sufficient time available to get out the weather fore- cast, especially in view of the increased demand for ocean weather and smaller area forecasts? ~ Under the provisions of the SOLAS, high-seas weather information (beyond 200 miles) will be delivered over the INMARSAT system. Coastal weather information (to a nominal dis- tance of 60 miles offshore) will be provided separately lay the coastal countries.

OCR for page 29
39 2. Will the system be responsive enough to get out weather warnings in a near-real-time basis with no chance of a warning being omitted? NOAA, the Coast Guard, and others involved in the evolving use of NAVrI~X need to take full account of user needs and concerns in this process. The committee is concerned that NAVIES, which will not be operational for several years in the United States, is marginally capable of handling the products available today and might well be overloaded with the addition of higher resolution products. Manne Facsimile and Radio Teletype The general consensus of the user community is that it is absolutely necessary to continue both of these services as essential broadcasts for marine weather and ocean weather information. The central issue in this discussion was the potential termination of some marine facsimile broadcasts by the Navy. The Navy began to use a facsimile broadcast for marine information more than 30 years ago. The broadcast was not encrypted and thus could be received by any ship at sea with the proper equipment. This broadcast became standard in the marine community and its basic scenario is copied by many other nations who have the capability and need to disseminate marine weather information. Currently the Navy, for internal reasons, is considering terminating the facsimile broadcast. A differentiation is needed as to whether the Navy is just going to terminate broadcasting the marine facsimile information (in that case some other agency, such as NOAA, could arrange for broadcast to be accomplished if funding could be found) or if the information itself will be withdrawn from release to a civilian agency and thus to the public. The latter case would, in the view of the committee, have a serious impact on vessel safety, and should have detailed review before the marine facsimile information is withdrawn At present there is no planned replacement for this service. RECOMMENDATION: Improve Forecast Dissemination. NOAA should develop a national strategy for marine forecast product dissemi- nation to users. Specifically, it should define the role of NOAA Weather Radio for supporting the marine community and configure the system consistent with that role; structure a national plan for implementing NAVIEX so that it is responsive to the need for expanded marine forecasting service; provide for a full-period national marine facsimile service equiva- lent to the existing U.S. Navy service; and

OCR for page 29
40 provide for such other services as necessary to support user needs. FINDING 6: THE NEED FOR NEW SYSTEMS FOR FORECASTING INTERNAL OCEAN WEATHER EXISTS There exists a common national interest in, and need for, nowcasts and forecasts of oceanic velocity, thermal structure, and related fields. Significant and sustainable benefits to a variety of commercial, military, and recreational oceanic activities are identifiable and are now for the first time feasible based on existing ocean science and technolog'. Nowcasting, as it applies to internal ocean weather, is a novel approach that integrates new and existing in situ and remotely sensed observations, and incorporates the data directly into realistic oceanic numerical mod- els to define existing and future oceanic features and states. Although the need for nowcasting and forecasting of internal ocean weather was not as strongly supported by the working groups as the more obviously observable phenomena such as storms and rogue waves, it was a consen- sus of the committee that future improvements to ocean forecasting are critically dependent on the development of this capability. Commercial development, marine operations, and recreational use require expanded nowcasting and forecasting capability for mesoscale oceanic phenomena and related boundary processes of the U.S. coastal ocean and deep ocean. The mesoscale phenomena (such as eddies, jets, and meanders) pre- dominantly occur on space scales of tens to hundreds of kilometers and on time scales of days to weeks. Related boundary processes (like fronts, up- welling, advection, thermocline, and shelf-deep ocean interactions) occur on similar spatial scales, but frequently have broader temporal variabil- ity. Many of the oceanic processes that directly affect the U.S. Exclusive Economic Zone occur over and near the break of the continental shelf. The forecast problem is of two types, involving (1) evolution via in- ternal dynamic and (2) the response to local atmospheric forcing. Internal dynamical evolution drives the internal "weather" of the sea; the oceanic mesoscale is dynamically analogous to the atmospheric synoptic scale. Re- sponse to local atmospheric forcing occurring at and near the ocean surface (principally within the mixed layer depth) occurs at generally faster rates than that of internal dynamical evolution. Prediction of oceanic mesoscale phenomena and related boundary processes has become feasible due to recent rapid progress in ocean science and technology. Advances in scientific knowledge of phenomena have occurred, which in turn are leading to new theories. New data are becoming increasingly available in "real-time." New and innovative platforms and instruments (land, ocean, and space based) are significantly increasing the availability of timely ocean observations.

OCR for page 29
41 Furthermore, predictive methodologies and techniques as well as pro- cessing capabilities are providing the essential tools to assimilate informa- tion and model the ocean. Significant advances during the past 10 to 20 years have made available supercomputers, data management and commu- nications systems, new numerical models with realistic dynamics and real data initializations, and four-dimensional data assimilation capabilities. Significant economic benefits can be realized by implementing now- casting and forecasting capabilities for oceanic fields. The fishing industry can benefit substantially from reduced search time, fuel savings, increased safety, improved resource management, and possibly even by the creation of entirely new fisheries. The shipping industry can benefit from efficient and safe use of ship time, fuel savings, and avoidance of cargo damage. The offshore oil and gas and offshore construction industries can benefit from avoidance of equipment loss, unnecessary production or construction time loss, and over-engineering. The U.S. Coast Guard can benefit from an increase in the number of lives saved and amount of property recov- ered, as well as efficient and economic resource allocation, fuel savings, and disaster avoidance. The U.S. Navy can benefit from more effective defense measures and effluent resource allocation and utilization. Many of the users share similar needs and can identify similar economic benefits, especially within the U.S. Exclusive Economic Zone. Improved nowcasts and forecasts of internal ocean weather and related boundary processes are well within the national means. The technology (ob- servation, processing, and communications systems) is feasible, and recent advances in scientific understanding (phenomenology theories and numer- ical models) have made timely prediction realistic and accomplishable. RECOMMENDATION: Advance the Capability for Forecasting In- ternal Ocean Weather. The nation should establish an operational capa- bility for nowcasting and forecasting oceanic velocity, temperature, and related fields to support coastal and offshore operations and management. Development of these capabilities will require the establishment of an observational network in areas of high priority. FINDING 7: EFFORTS ARE NEEDED TO UNDERSTAND AND OPERATIONALLY FORECAST EPISODIC WAVES AND EXPLOSIVE CYCLOGENESIS Episodic Waves Leo distinct areas of marine weather were especially troubling to a significant number of users. The first area dealt with the occurrence of high waves known as episodic waves, more commonly known as "rogue" waves. These waves occur without warning and are uncommonly large for

OCR for page 29
42 the sea states in which they are embedded. Although a body of literature exists on this phenomena dating back to the 1960s, no single mechanism or interactive series of events has been proven to be the cause of these waves or groups of waves such that the events are predictable. The major user impact of these episodic waves is felt by ships operating on the high seas and the open-ocean tuna fishery. In the case of these smaller vessels, it has been speculated that an encounter with episodic wave events may have been the cause of the loss of entire vessels and crews. Even for major vessels plying the world's sea lanes, the occurrence of such episodic waves Is a significant problem, as noted by the following remarks made at the committee's workshop: Mariners consider the occurrence of [meteorological] surprises as the governing threat to safety of transoceanic passage. In spite of all this [weather information] we still hear cases of severe cargo damage and loss of vessels. These are usually caused by large waves. We [the shipping industry] would like reports of certain areas designated as likely high wave problem areas and if possible a degree of probability regarding what wave heights, direction, and frequencies of such large wave patterns can be expected. Every so often there come a series of three waves that appear out of nowhere, you're not expecting them, you're not prepared. The consensus of the committee was that there is a body of anecdotal evidence to suggest the occurrence of waves dramatically larger than those anticipated on the basis of prevailing sea conditions. There does not appear to be technical consensus as to whether episodic waves reflect a particular physical phenomena or are instead merely a manifestation of the statistical variability within a given sea state. The cause notwithstanding, these events are perceived as a significant problem to the general mariner in terms of vessel, cargo, and financial damage and can result in the loss of life. No federal agency presently undertakes to forecast this phenomena. Explosive Cyclogenesis The second area of concern is the "surprise storm" referred to by scientists as explosive cyclogenesis. Explosive pyclogenesis describes ex- traordinary, low-pressure systems that deepen at rates of 1 millibar per hour or faster. Such storms are not well forecast by the National Weather Service. A common event in the winter months on the Eastern Seaboard is to hear that a local storm has moved on and "has passed harmlessly out to sea." With some troubling frequency these storms can suddenly strengthen, with central pressures falling much more rapidly than had been forecast, and the mariner's "surprise storm" has been born. As with episodic waves,

OCR for page 29
43 these events are rarely forecast and can catch the vessel operator ill pre- pared for heavy weather, resulting in damage to or loss of the cargo, vessel, or personnel While the primely damage by explosive cyclogenesis is to vessels op- erating on the high seas, vessels and operations taking place in more nearshore regions can suffer damage from large waves propagating out- ward from the area of the storm. This is also the case for inshore activities such as dredging, which is extremely weather sensitive, and other forms of . Ocean engmeenog. Explosive cyclogenesis has been the subject of study in a series of field experiments undertaken by the Navy, NOAA, and others. These initial research efforts will eventually improve our understanding of these phenomena. Research to this end needs to continue. Additional detailed discussion on explosive cyclogenesis and episodic waves can be found in the reports of Working Groups 2 and 4 (Appendixes F and H). The user community, primarily high-seas vessel operators, would like better forecasts of these events and especially warnings, by area, when conditions exist that favor such explosive storm formation, or when a specific storm has the potential for such explosive deepening in pressure gradient that can cause onset of high winds and increasing sea state. RECOMMENDATION: Research on "Bomb" Storms and Rogue Waves. The federal government should develop the capability to forecast both episodic waves and explosive cyclogenesis.