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--including east of the Cascades.
    •     This report describes the situation and what needs to be done to correct it.
    For more information:  Cliff Mass, Professor of Atmospheric Sciences, University of Washington (206-685-0910), cliff@atmos.washington.edu

     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, describe 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 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 not for the surface, but for 10,000 ft.  Radar coverage near the surface is far less, particularly over the western U.S. where blockage by terrain in significant.  Even from the optimistic 10,000 ft coverage, the Northwest coastal zone is poorly served compared to the California, Gulf, and Atlantic coastal regions.
     
     

    The National Weather 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 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 (coverage at 3-km, approximately 10,000 ft), with hatching indicates
    substantial blockage. Coverage at lower levels is far worse.




    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.  Doppler radar winds along the coast are not available at all.  The Medford radar is even more problematic:  it is located at a very high (7500 ft) elevation to avoid minimize blockage, causing it to miss most coastal and valley precipitation.  The Medford radar is also too far inland coast to provide  useful information over the coast.  One has to go south to California (the Eureka radar) to get proper coastal radar coverage.
        These figures and 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.
  •  Crucial offshore military exercises run out of Whidbey Island Naval Air Station, McChord Air Force Base, the Everett Port, and the Bangor Submarine base are without the comprehensive meteorologist 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 and high winds never materialized.  A coastal radar would have provided an accurate location for the low 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.

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



    What Would We See With a Radar on the Northwest Coast?

        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 Washington Coast near Westport.  The images from this period provides a wonderful 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 image (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 only showed only light precipitation along the Oregon and nothing north of the Columbia River, when in fact substantial precipitation actually occurred.


    S-Pol 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.

    9 January 2001 at 1900 UTC (11 AM PST):  At this time the S-Pol radar showed a heavy shower approaching the Oregon and Washington coasts. The Camano Island radar did not show the heavy rainband at all and just indicated some light shows off the Northwest coast.  The lack of any precipitation along the central Washington coast on the Camano radar is the result of total blockage by the Olympics to the southwest of the radar.  The Portland radar indicated nothing north of the Columbia River and greatly underplayed the intensity of the feature along the Oregon coast.


    S-Pol Image


    Camano Island (left) and Portland (right) radar images at the same time.

    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 Florence.   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, probably involving an initial investment of approximately 5 million dollars (based on conversations with individuals in the NWS Office of Meteorology) and recurring costs of several hundred thousand per year.  But such costs are small compared to the substantial benefits such coastal radars would provide.  It is of interest to note that a  Seattle TV station (KCPQ-13) was able to afford to place a Doppler radar on the coast at Neah Bay.  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 clearly 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 direct the National Weather Service to establish Northwest coastal radars and to provide the necessary funding.  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.