Thursday, March 17, 2016

Was Sunday's Storm Like a Hurricane?

Several media outlets have described last Sunday's blow as similar to a hurricane.   Is that true?   Are there any similarities of our modest windstorm with hurricanes?  Let's check it out.

First, let me start with an impressive water vapor satellite image that shows the amount of water vapor in the upper troposphere, with green being the most, followed by white, gray and black. Amazing spiral, with intervening layers of moist and dry air spiraling in towards the center.

The infrared satellite picture (giving the temperature and thus the height of the clouds) shows the spiral, with the speckled clouds indicating cold air moving into the system.

The structure of hurricanes is radically different.  There is no spiral of moisture into the storm, no dry air or cold air spiraling towards the center.   Rather, there is a relatively uniform area of high moisture values associated with the eye wall clouds and the moist surroundings.   Here are two examples from real hurricanes.

Hurricanes form over tropical waters and require a warm, moist environment....dry and cold air spiraling towards the storm center would kill it.

Then there is the energy source of the Sunday storm and hurricanes.  Very different.  Midlatitude storms derive their energy from horizontal temperature contrasts (or gradients).  Hurricanes need warm water (more than roughly 80F), which provides both sensible heat and moisture.    You know what the temperature of the eastern Pacific off our shore is right now?  As shown by the NOAA  sea surface temperature map, around 10C (50F).   No true hurricane could survive over the northeast Pacific.

Hurricanes have sustained winds exceeding 64 kt (74 mph).  Sustained winds NOT gusts.  During the height of our storm, the strongest sustained winds were roughly 25-35 kt, with a few locations with the best exposure (like West Point, Seattle) getting into the 40s kt.  Not even close to hurricane levels.  For example, at the extremely well exposed UW Atmospheric Sciences site (on top of a 7 story building), sustained winds only reached around 25 knots (see below), with gusts hitting about 40 knots.

I could provide more illustrations and reasons, but the facts are clear.  Sunday's storm was not a hurricane, did not have winds even close to that of a hurricane, didn't have the structure of a hurricane, and derived it energy from a very different source.  Completely different animal from the tropical hurricanes striking the SE U.S.

Yesterday I talked to an experienced arborist, who told me that one reason so many trees fell during this event was due to the extraordinary saturation of our soils after the wettest winter in Seattle history.


Unknown said...

Dear Cliff,
I've long admired your meteorology as well as your often courageous stands exposing institutional dysfunctions. So my question this morning is this: While I do not own a television, just now while visiting in-laws who leave the screen on all the time, I cannot help but have been stuck by the epic disconnect between the mainstream "weathermen" going on about local temperatures and the size of hailstones in Arkansas, and no mention, not a single breath about NOAA having confirmed February as having had the greatest global temperature anomaly in recorded history, approaching the critical 2 degrees C increase. Now I am well aware of the important distinction you often make between weather and climate, but this seems like a vast institutional dereliction, that these mass media outlets utterly ignore this news whose importance so tremendously outweighs those hailstones. So what's up with this meteorological chunk of the media industry? Are they, like FOX news in the thrall of corporate black money? How can people be awakened to what is breaking over their heads?

Cliff Mass said...

TV weathercaster provide weather forecasts...that is their role. Most have little or no background in climate matters, so they are not the ones to be commenting or analyzing such trends. The general media give a lot of attention to climate change--I suspect few people are unaware of the issue. Keep in mind this year's warm is revved up by El Nino...cliff

Mark said...

Looks like a typical comma cloud to me.

Except for northern California, the rain situation for California looks bad.

Look at all the dead trees in Sequoia National Park:
Many of these trees died during last summer's extreme heat and drought.

Last February was very warm and dry across much of California. The remainder of March looks very warm and mostly dry across all but northern California.

After March, the probably of significant rain in southern and central CA is low.

Puget Sound:
A couple weeks ago we had ocean flooding during high tide on Vashon and around the Sound. Old timers on Vashon tell me they have never seen the water reach places it did. The tide waters floated large logs onto low lying roadways and into yards. I'm disappointed Cliff did not address the tidal flooding. I guess you have live near the Sound/ocean to notice.

Nuisance ocean flooding is increasing.

Winter Arctic ice is at record lows. The Global temperatures anomaly is at record highs.

February's global temperature anomaly of +1.32 C (NASA) will probably decline a couple tenths of degree C next year after the central Pacific reverts to ENSO neutral or La Nina conditions. But this summer, there will be some record heat waves around the world. Hopefully, western Washington will be spared.

We are still below the 1.5C anomaly that many climatologists regard as the threshold for significant climate change. So AGW deniers still have a couple decades to ply their political hoax that AGW is not real.

Beth Niquette said...

I found your assessment to be fascinating. I lived through the Columbus Day Storm, which was more like a hurricane. I read once that hurricanes are called cyclones here on this side of the world. Sunday's storm was not like that one at all. I like the description and your analysis very much. Thank you.

sunsnow12 said...

Cliff - You left out the "Weather Service Says" part of the Seattle Times headline.

2nd paragraph in the article: “Storm looks like a hurricane! The central pressure is deeper than expected, 978 mb,” the National Weather Service vented on Twitter around 1:30 p.m., with a photo of the eye of the storm offshore from Olympic National Park.

As you point out clearly (and factually), this storm never once "looked like a hurricane", nor acted like one, nor was derived as one.

The Seattle Times wants pageviews. What is the excuse for the NWS?

Jort Sandwich said...

Is it still time to "Stop the El Nino Forecast Complaints"? Was the celebration and defense of a fully successful El Nino forecast back on January 31st premature?

Admit it, Cliff: You guys HISTORICALLY BUNGLED the El Nino forecast this year. We are SOAKED.

Westside guy said...

Cliff can (and may! haha) correct me, but while El Niño is usually associated with slightly drier/warmer than normal winter weather... I believe the strongest correlations are actually with spring weather. So it's probably a few months too early to declare a bungled forecast.

Plus, it's just probabilities. Individual seasons can diverge dramatically from what's expected. One of the driest winters I remember was actually a La Niña winter.

You may win occasionally betting against the house, but it's still not a good long-term strategy.

RLL said...

The 'looks like' was OK, but should have been followed quickly with 'but isn't'. And a quick explanation of where the power of the two types of storms come from. Pubic announcement flub.

Westside guy said...

Of course, while this scientific analysis of the storm is interesting... to definitively answer the title's query a completely different question must be asked:

Did, or did not, Sunday's storm "rock you"?

Bob said...

The afternoon Langley radar looked pretty cool...