Friday, January 6, 2017

The Unusual for the Northwest: An Inferior Mirage

It is the mirage that we rarely see over water in the Northwest:  an inferior mirage in which objects look much lower than they actually are.

 In this blog I have frequently talked about summertime superior mirages over Puget Sound, in which warm air over cold water creates an atmospheric lens that makes objects near the water loom upwards in height.   Here is an example of one provided to me by Skunk Bay weather cam master, Greg Johnson, in chich the coastal cliff's loom upwards.


But during the last few days, we have had the opposite situation in very cold air (15-25F) has moved over the relatively warm water of Puget Sound and adjacent waterways (all around 48-50°F).   This warm water warms the air immediately above.

Cold air over warm produces a lens effect that results inferior mirages, in which objects are seen lower than they actually are (see schematic below).


 A frequent example of an inferior mirage is on hot summer days, a very warm roads heat the adjacent air, with cooler air above.   Light from the sky is bent down, giving the impression of water on the road, when it is actually light from the sky that provides the watery look (see below).  Inferior mirages often invert objects as they push them downwards.


As noted earlier, today we had cool air above warm water.  Furthermore, winds have been relatively light, which reduces mixing of air in the vertical.  Greg Johnson, located on Skunk Bay of the northern Kitsap Peninsula took some excellent pictures this morning of inferior mirages.  Here is a good example.  The top of the light color cliffs are push downward, as is part of the ships bow (which is also inverted).


A close-up shows the action better.


An image of a ship (the Evergreen) shows a similar downward displacement and inversion of features.


Another "mirage" have been the suggestions of moderate snow over the Puget Sound lowlands.   On Saturday, precipitation in some sea level locations will start as snow (Saturday evening), but will rapidly turn to rain.

13 comments:

Eric said...

I don't believe the bow appears inverted, we're seeing the wave over the bulbous bow at the waterline.

Unknown said...

Mirages are interesting. However, we've got all sorts of interesting weather happening in the U.S. right now. Not in the least, the forecasts for south of us in Oregon and California. Please give us your thoughts/predictions on these Prof. Mass.

Kelly said...

NWS just issued a Winter Storm WARNING for the Hood Canal region. Your thoughts?
I live in Seabeck

Gladys Gravyboots said...

The ~8" of snow we got in the SnoCo foothills on New Year's is still light & powdery, unusual but an excellent illustration of the low humidity.
UW Zone forecast predicts the freezing level rising to 2500' Sunday & I can't wait!! So tired of snow, ice & frozen water supply...

tmoose said...

I believe the mirage phenomenon is called "fata morgana".

Matt said...

Yes, would love if you discussed Oregon weather a little more..

Alex Maas said...

That kind of looks like a normal RO-RO (roll on roll off) car carrier, they are slab sided brutes. Bow looks kinda normal like Eric says.

Z said...

It always seems to me that mountains loom larger after a snowfall followed by clear air. Would love an explanation of that.

Gary said...

Will someone please help me see what Cliff describes in the final photo of the good ship Evergreen? Like where in the photo is a ship located? E.g., "halfway over from the left and 1/3 way up from the bottom".

And, without an "un-miraged" image of the ship in the previous image, I don't see what part of it is distorted/inverted as a mirage.

LewisLucanBooks said...

Anyone know what's up with Langley Hill radar? Been down more than up, the last several days. Since I live just SE of Cheahlis, this fairly new radar instillation has really enabled me to "see" what's coming at me. It is missed .... Lew

WQR said...

Gary said: Will someone please help me see what Cliff describes in the final photo of the good ship Evergreen?

I assume it is the white hourglass shape (and the darker shape) at the bow of the ship. It looks like it is perfectly inverted from the midpoint of where it narrows. Eric and Alex say it is just the wave over the bulbous bow at the waterline but I'm not sure that would look so symmetrical.

SkunkBayWeather said...

After the blog, I put together an image that shows a little more detail. I took another picture of the ship as it went by out front that day. I cropped the original photo (taken 15 miles away) and then cropped the close-up and aligned them proportionally on one image. They are aligned at the deck level. This really shows the difference. http://skunkbayweather.com/InferiorMirageComparison.jpg

Mosier Fire Chief said...

We see these inferior mirages on the Columbia River from time to time. Happened today in a very limited area.

Years ago I saw something like this from the air, flying in to SeaTac in very cold weather. Looking across the Sound, the Olympics appeared to be raised on pillars, as if the foothills were stretched vertically. No photo, sadly. One of the weirdest things I've seen.

Have also seen the mirage of objects over the horizon appearing above the horizon and inverted -- once an island from Resolute, Nanuvut (Inuits call this mirage "bobbing up", and once a ship sailing upside down into the Golden Gate from Stinson Beach.