Why the Strange Radar Echo over the Pacific Ocean?

I have gotten quite a few emails asking about a strange radar echo off the Washington Coast, including a few claiming a secret military operation and one suggesting an alien presence.

Here is an example, showing the Langley Hill radar on March 15th at 0503 UTC (10:03 PM March 14th PDT).  The is one of the lowest scan angles:  0.5 degrees.  Radars are tilted at various angles in the vertical and scan around in direction (azimuth). 



You see the echo off of Hoquiam?  That is what I am talking about...and here is an expanded version


Two hours later...still there.  Very strange.  A meteorological feature would not do that.


When the radar is scanned at a higher angle (1.3 degrees), the echo goes away.  Bizarre!



But at the lowest possible scan angle  (.176 degrees), the echo gets stronger!



Pesky aliens again or more secret flights from Whidbey?   I wish, it was so exotic.

In reality, the radar beam is hitting the ocean and reflecting/scattering back to the radar antenna.

When the radar signal leaves the radar, it moves out as a cone that widens with distance.  The Langley Hill radar near Hoquiam and all National Weather Service radar beams have a width of 1 degree, which means most  (but not all) of the energy stays in a 1-degree cone.  And note that the cone widens away from the radar.


The Langley Hill, like all NWS radars, scans at various angles as it circles around in what is called a scan strategy (see example below).    Note how the beams widen and reach higher elevations away from the radar.   

When the Langley radar was installed, all NWS radars but one had their lowest angle at 0.5 degrees above the horizontal.   The ONLY radar allowed to go lower was OURS at Langley Hill...and you can thank U.S. Senator Maria Cantwell for that.  More recently, a few radars have been allowed to have angles below 0.5 degrees.
So why is the echo offshore of Hoquiam?  
Answer: The lowest bean from the Langley Hill radar is hitting the Pacific Ocean and reflecting back to the radar.  That is why the echo is stronger fore for the lowest beam and goes away when the bean is elevated.

And there is a fun way to prove this is not a real meteorological target.  Langley Hill is a Doppler radar that provides the speed of the echo towards or away from the radar.   Below is the Doppler velocities at the same time as the first image above.  No velocity towards or away from the radar (light gray color)!  Most meteorological targets are moving because of the wind.


  


I will try to have an open mind about other explanations.


Comments

Post a Comment

Popular posts from this blog

The Time of Year You Can See the Air Move

Image
  Most of the time, you can not see the air move.   You can feel it, but the complex, turbulent motions are invisible to you, except when it interacts with leaves and branches on trees and plants. But for a few weeks of the year, the sky is full of small, cotton-like tuffs that like a natural MRI machine reveals the complex three-dimensional motions of the atmosphere.   Cottonwood season.  And we right in the middle of it.   Being cottonwood aware is of particular value this year.  It reveals the active dispersion and movement of air that makes the outdoors essentially COVID safe, and thus should be of some comfort for those nervous about transmission outside. Cottonwood seeds are embedded in small cotton-like fibers.   A million seeds weigh about 3 pounds.  Yes, each seed and tuff weights about .000003 pounds.   And that fact, plus the cottonwood tuff, means that these seeds fall VERY, VERY, VERY slowly.   So slowly that they are excellent markers for the three-dimensional flow of the
Read more

Why so little lightning in the Pacific Northwest? And a very nice weekend ahead.

Image
During the past 24-hours, there have been a few lightning strokes over the region (see below) but nothing to write home about (see below). It turns out that the Pacific Northwest and the remainder of the West Coast have some of the lowest frequencies of thunderstorms in the entire country (see below). But why?    My podcast provides the answer. And I also give the weekend forecast....and I think most will like what I have to say. To listen to my podcast, use the link below or access it through your favorite podcast service. Some major podcast servers:     Like the podcast? Support on Patreon 
Read more

Strong Atmosphere River Heads into British Columbia and Southeast Alaska

Image
While the Northwest has been drier than normal, it has been drenching wet a few hundred miles to the north. An unusually strong atmospheric river ....a long current of moisture stretching southward to the subtropics...has been in place for days, bringing large amounts of water vapor to Alaska.   And the atmospheric river will be in place for several more days, slowly moving southward. To illustrate, the scale and beauty of the atmospheric river, here is a water vapor satellite image for 11 AM today. The lighter areas have more water vapor.  You can see the current of moisture extending from near Hawaii into central BC.  This current is the result of low pressure over the Gulf of Alaska and high pressure offshore of California.   A forecast of total water vapor content in the atmosphere for 11 PM tonight shows a healthy atmospheric river (white and blue colors indicate the higher amounts of moisture). As this atmospheric river slams into the mountainous West Coast, the air is forced to
Read more