The Pacific Northwest has the Worst Coastal Weather Radar Coverage in the Continental U.S.:  Documentation of the Problem and a Call for Action
 
 


A National Weather Service WSR-88D Doppler Radar

  • There is little useful weather radar coverage over the Northwest coastal waters or along the immediate coast.
  • Northwest meteorologists lack radar information about crucial weather features along the NW coast, such as heavy precipitation and strong winds.
  • In contrast to the rest of the country, Northwest weather forecasters cannot view the details of weather systems approaching the coast.  As a result...
  • The lack of a coastal radar degrades warnings and forecasts for the entire region from what could be possible with proper coverage.
  • Research on Northwest coastal meteorology is greatly hindered by the absence of an operational coastal radar.
  •     This report describes the situation and what needs to be done to correct it.


     Background:

         The National Weather Service has recently completed a major modernization, a central component being the installation of powerful Doppler weather radars across the country.   Such units, known as WSR-88Ds or NEXRADs, provide the distribution of precipitation and winds in their environs and have revolutionized forecasting and meteorological research.
        The range of useful radar coverage is controlled by a number of factors.  Terrain blockage is important in mountainous regions like the Northwest.  Furthermore,  the height of the radar beam increases with distance from the radar--resulting in an inability to see important low-level features far away from the radar.  Under perfect conditions, the maximum range of the WSR-88D to get wind information is 230 km (138 miles).
        An official National Weather Service map of national weather radar coverage (for precipitation) is shown below.  A second image with a blow-up of the Northwest section is also provided.  These radar coverage maps are valid at 10,000 ft ABOVE THE RADAR SITES (many of which are already thousands of feet above the surface!), not at the surface.  Radar coverage near the surface is far less, particularly over the western U.S. where blockage by terrain is significant.  Even from the optimistic 10,000 ft coverage, the Northwest coastal zone is poorly served compared to the California, Gulf of Mexico, and Atlantic coastal regions.  But as shown below, the NWS radar coverage maps do not show the real story.
     
     

    The National Weather Service installed three radars to provide coverage over western Washington and western Oregon:  Camano Island (WA), Portland (OR) and Medford (OR).  The figures shown below indicate their locations and provide more exact coverage maps using high-resolution terrain.


    The left diagram shows the location of the National Weather Service radars (tower symbols)
    and some other sites of interest.  The right diagram indicates the effective coverage of the
    Weather Service radars (at 3-km, approximately 10,000 ft above mean sea level), with hatching indicating
    substantial blockage. Coverage at lower levels is far worse.  Notice that coastal coverage is virtually absent.

        The Camano Island and Portland radars are blocked to the west by the Olympic and coastal mountains and provide little information about  weather over the coast and the near-offshore waters.  Even without the mountains, these radars are positioned too far inland to provide useful information about weather systems approaching the Washington and Oregon coasts.  The Medford radar is even more problematic:  it is located at a very high (7500 ft) elevation to minimize blockage, causing it to miss most coastal and valley precipitation.  The Medford radar is also too far inland to provide  useful information over the coast.  One has to go as far south as California (the Eureka radar) to get proper coastal radar coverage.
        These figures, and the experience of Northwest meteorologists, demonstrate that the coastal regions of Washington and Oregon have extremely poor or non-existent radar coverage--demonstrably the worst radar coverage of any coastal region of the continental U.S.  Such poor coverage is particularly disturbing considering the powerful weather systems that make landfall over the area, the continual threat of heavy precipitation and flooding over the Olympics and coastal terrain, and the intense use of the near-shore waters for fishing, shipping, recreation, and military exercises.  Some important considerations:
     

  •   The western entrance to the Strait of Juan de Fuca and the dangerous Columbia River bars do not have useful low-level weather radar coverage.
  •  Offshore military exercises run out of Whidbey Island Naval Air Station, McChord Air Force Base, the Everett Home Port, and the Bangor Submarine base are without the comprehensive meteorological oversight that coastal radars could provide.
  •  Weather Service forecasters cannot garner critical information on weather systems approaching the Northwest coast, clearly degrading short-term forecasts.  For example, on 15 May 2001 the National Weather Service had to deal with a difficult situation, as a small low pressure system approached the Washington Coast.  Satellite imagery was inconclusive, and without a good observational fix on the system, the NWS forecaster was forced to follow the computer models which indicated the potential for strong winds over Puget Sound.  Unfortunately, the low went farther north than the computer models predicted and the high winds never materialized.  A coastal radar would have provided the exact location for the low center hours before landfall and a far more accurate forecast could have been made.
  •  Incidents such as the grounding of the New Carisa and the loss of Coast Guard personnel during a rescue attempt in 1997 demonstrate the need for timely weather information over the Pacific coast for emergency situations.
  • Doppler winds from the Weather Service radar are only available within 230 km (138 miles) of the radar.  Considering that the nearest coastline is 160 and 100 km away from the Camano Island and Portland radars, respectively, offshore wind coverage would be very limited.
  • Radar beams ascend higher the farther they get from the radar.  By the time they get to the coast (approximately 150 km out), the radar beams are already at approximately 1500 m (approximately 5000 ft).  Thus, current radars cannot determine low-level coastal and offshore precipitation and wind features of great interest to mariners and people living on the coast, even if the coastal terrain wasn't there.


  • When the New Carisa grounded Near Coos Bay, Oregon, there
    was no radar coverage to help manage salvage operations.





    What Would We See With Radars on the Northwest Coast?

        To illustrate the kind of radar coverage two coastal radars could provide, the potential coverage of the lowest radar beam for the current and proposed radar networks is shown below.  The current network (left figure below) provides little radar coverage along most of the Oregon and Washington coasts, and what coverage does exists is for higher altitudes. In contrast, northern California enjoys excellent coastal coverage due to the Eureka radar site. Wth the addition of two radars along the coast at Westport (WA) and the central Oregon Coast (perhaps Newport), the Pacific Northwest gains excellent coastal radar coverage, allowing a clear view of storms approaching from the Pacific.
     
     


    Radar coverage maps for the lowest beam (.5 degree elevation angle) for the current
    network (left) and the proposed network (right) with radars at Westport (WA) and
    along the central Oregon coast.  Red areas indicate no coverage below 8000 m (25,000 ft).
    Note that someof the coastal terrain without coverage would be included at a higher scanning angle.





        During January and February of 2001, a research radar (the NCAR S-Pol), similar in capabilities to the National Weather Service WSR-88D, was placed on the central Washington Coast near Westport.  The images from this period provides an opportunity to determine what a coastal radar could do if the investment was made.  Below you can view a few examples.



    23 January 2001 at 1548 GMT (7:48 AM PST) The S-Pol radar (shown below) indicates a strong front with heavy rain approaching the Oregon and Washington coasts from the southwest.  If available operationally, such information would have provided coastal communities with an early warning of the potential for heavy rain and a substantial change in the winds. The Camano Island radar indicated nothing, while the Portland radar  showed only light precipitation along the Oregon coast and nothing north of the Columbia River, when in fact substantial precipitation actually occurred.


    S-Pol Coastal Radar Image

    Camano Island (left) and Portland (right) radar images at approximately 1550 UTC on 23 January 2001.
    The lowest radar scans (.5 deg) are shown.


    What would be the benefits of additional coastal radars?
  • Meteorologists would be able to see the details of incoming weather systems during the 6-18 hr period before they arrived.  Forecasts and warnings for the entire Northwest would improve.
  • Coastal search and rescue, as well as offshore military operations, would gain critical weather radar information on winds and precipitation.
  • The data from coastal radars could help provide a real-time detailed description of the weather in the coastal zone.  Not only could this information be provided to the public and interested users, but it could be used in numerical weather prediction models to improve downstream predictions.  Such data is particularly critical in the Northwest where we lack detailed observations upstream over the eastern Pacific.
  • For the first time, the distribution and intensity of coastal precipitation could be diagnosed, aiding more accurate streamflow and flood forecasting.
  • Researchers would gain a continuous view of the interaction of Pacific weather systems with Northwest coastal terrain, thus improving our understanding of these features, which should lead to better forecasts.
  • The radar would provide crucial data for homeland security needs.  For example, the data from the radars would enhance local weather prediction, thus providing better forecasts of toxic plume dispersion.  It would also help protect the population from major storms.
  • What needs to be done?

        To address at least one and more optimally two additional Weather Service radar need to be place on the Pacific Northwest coast.  With two radars, one radar could be place on the central Washington Coast--Westport would be a good placement--with the other radar along the central Oregon Coast, perhaps near Newport.   If only one radar could be acquired, the central Washington coast would probably be the best location, since it would provide surveillance for the entrances to both the Strait of Juan de Fuca and the Columbia River, would provide crucial precipitation information over the flood prone southern flanks of the Olympics, and would give upstream weather information for the highly populous region stretching from the northern Willamette Valley to Puget Sound.

        The acquisition costs for an additional radar would be substantial, with installation costing approximately 4.5 million dollars, with additional costs for utilities and maintenance each year (approximately $500K per year).  But such costs are small compared to the substantial benefits such coastal radars would provide.  A single improved forecast could save millions of dollars and several lives.  It is of interest that several local TV stations have been able to afford weather radars (although far less capable than the NWS units).  Surely, the U.S. government could make a similar investment.  Other regions of the country have requested and secured additional radars to fill in holes in coverage.  The Pacific Northwest has a strong claim to similar treatment.

      How do we proceed from here?  Perhaps the best approach would be to contact our representatives in the Senate and the House of Representatives, asking them to supply additional funds to the National Weather Service to add one or two Northwest coastal radars.  (Click here for Senatorial contact information).  Additional funds are crucial because the NWS does not have support for extensions to the current radar network.  It would also be useful to directly contact higher officials in the National Weather Service and NOAA, letting them know about our concerns regarding this major deficiency in the national observing network.

    For more information:  Cliff Mass, Professor of Atmospheric Sciences, University of Washington (206-685-0910), cliff@atmos.washington.edu

    Acknowledgment

        Ken Westrick of  . provided several of figures shown above and provided several useful comments.