Summer Thunderstorms

An area of summer thunderstorms and cumulus convection is moving through tonight, and for many of you this is the first rain in weeks.

Let's look at recent radar imagery every two hours.

5 PM:  lots of showers on the coast and offshore.

7 PM:  the coastal showers moved inland and substantial thunderstorms hit eastern WA.

9 PM:  Puget Sound gets moistened and a very heavy show (red color) is moving through south of Yakima

The 12-h totals as of  9 PM, modest precipitation is found around the region.  Few hundredths to a few tenths in general.

The cause?  The classic NW convection pattern.  A trough or low off the coast and a trough embedded in it moving across the region (see graphic).

That plus air that was primed for convection and only required a bit of lift to get it going.  One measure of this potential is something called CAPE...Convective Available Potential Energy.  You can think of it as the amount of energy that can potentially be released by buoyant convection.  Today, the values got up to a few hundred Joules per Kilogram...quite respectable for around here (see graphic). But pathetic in the Midwest and upper Plains.

The approach of the trough/low provided the lift that released the instability.  I flew in tonight from California and was impressed that some of the convection looked like it reached 20-25 thousand feet.  Substantial for these parts.

Halos and contrails: Is there a connection?

The short answer is YES!

Today I received pictures from several of you regarding some wondrous halos in the sky.  Others noted an  impressive collection of contrails...and there is no accident that both apparitions appeared at the same time:  the ultimate cause is the same.

Here is a very nice picture from Brendan Fields showing both appearing at the same time!

And from Jules submitted to the Seattle Times:

 A high resolution MODIS image from today shows an extensive collection of high cirrus and cirrostratus clouds  and if you look carefully you will see lines:  those are contrails!

Halos occur when rising air in the upper tropospherc causes condensation and the formation of ice crystal clouds (cirrus and cirrostratus).   When the sun's ray's intersect the randomly oriented ice crystals, the light is bent preferentially by 22 degrees...thus producing a 22 degree halo.

Contrails occur then the air is very near or at saturation, and the addition of water vapor from the combustion in the jet engines causes the formation of a line the of clouds behind the plane.

So both halos and contrails are dependent on the upper troposphere (roughly the layer of the atmosphere from roughly 15,000 ft to 35,000 ft) become saturated or near saturated.   We can tell whether this is true of the real atmosphere by taking the observations from balloon-launched weather instrument radiosondes)  and plotting the temperature and dew point temperature on a chart (a.k.a. a sounding).

Below is the sounding from Quillayate, on the Washington coast, at 5 PM Saturday.  Note the temperature lines (red) and dew point lines (blue) are very close together from 500 hpa (around 18,000 ft) to around 350 hpa (around 25,000 ft).    The atmosphere is either at or close to saturation in this layer (saturation is evident when the temperature and dew point are the same) .

This saturated layer is associated with rising motion from an east Pacific trough/close low (see image of upper atmospheric flow at 2 PM this afternoon), the ultimate cause of both the halos and contrails seen today.

Can You Get More than 100% Solar Energy? The Answer is Yes!

More and more folks are putting up rooftop solar panels here in the Northwest.  And some of them are getting results that seem bizarre.

Take the case of Ted Weiler of Kenmore, WA, who sent me a note that other day wondering why he sometimes gets higher peak solar output from his panels during partly cloudy days than clear ones. 

Here is a plot he sent me for his system output for a few days during the past week.  The green line shows the power produced on June 4, a day that was nearly clear.  Nice cosine shape.   The blue line/area shows the output on June 9th, a partly cloudy day---something very strange is going on!  At some times the solar power output was GREATER on the partly cloudy day than on the clear day.  How could that be?   And an even cloudier day is shown with the red line...even THAT day had a period with greater output than the clear day.

Can this be right?   Lets check the solar radiation measured on the roof of the atmospheric sciences building at the University of Washington.  First, lets look at the amounts on June 3, 4, and 5 (the times are in GMT/UTC, so they are offset 7 hr from PDT).   June 4th, the middle one, almost looks like a perfect cosine.  The 3rd and the 5th had some clouds.  But wait!  Look carefully and you will see that the partly cloudy days had some spikes (associated with clouds) that had peak values greater than the clear day.  Ted Weiler might be on to something!

Let's check out a different trio of dates (June 6, 7, and 8).  You can see the spikes above clear sky values again!  What is going on?

The answer is obvious if you think about it.  On partly cloudy days, we have periods with breaks in the clouds when you get direct solar radiation from the sun.  But you ALSO get solar radiation that is reflected off nearby clouds...solar radiation that is not getting to someone else because the cloud is intercepting it.   So you start with the clear-sky value direction from the sun, but you are also getting the radiation reflecting off clouds....the sum is clearly more than the clear sky value.

Here is the view from the top of my department at 2:30 PDT on June 9th.  It was partially cloudy at that time, and you can see some of the bright clouds that were giving the direct sunlight an extra boost.

Although you might get a boost above clear skies values for a short while, inevitably the direct solar radiation will get blocked by a cloud--thus, your total power output will be less than the clear sky total over the entire day.  If you can find a way to stay in the direct sun, while clouds surrounded you and never blocked the sun...you would have a really sweet situation.  My god, I know such a place.!..it is known as Sequim and its famous "blue hole."  No wonder so many California retirees are heading there, solar panels in tow.

Rainier's Shadow

Mount Rainier is perhaps the most famous landmark in our state...and it can cast the most amazing shadows.  This morning with a relatively uniform cloud deck that topped out around 6500 ft, the mountain's shadow was quite evident. For example, the 5:30 AM visible satellite image clearly showed Rainier's shadow and that of Mt. Adam.

And during the next hour or so, it quickly shortened.

And, of course, if there is a higher level cloud deck the shadow can appear on the bottom side of the clouds, as illustrated by the next two pictures.

Chuck Graham captured the upper photo from nearby Roy, Wash.

If aliens arrived at our planet, there is no doubt this mountain would be their first stop.  This conjecture is supported by the fact that the first flying saucer was observed over Mt. Rainer in 1947 by pilot Kenneth Arnold.

 Something to ponder....

Using Unmanned Aircraft for Severe Thunderstorm Prediction and Warning

After the tornado outbreaks in Moore City and Oklahoma City, Oklahoma, there was a flood of controversy about the role of storm chasers.   With the tragic loss of three experienced storm chaser/scientists, the injury of the several Weather Channel chasers (see picture below of their car), and the veritable traffic jam of chasers in the immediate vicinity of the Oklahoma City tornado (see image), a number of observers have suggested that there must be a better way of observing tornadoes.

Furthermore, when a severe thunderstorm pops up in an unexpected location (and this happens plenty of times), there are often no chasers in the neighborhood to give the National Weather Service ground-truth observations.

Position of storm chasers (with GPS and who reported their position) during the Oklahoma City tornado event.   There were certainly more chasers than this in the area.  The background image is the Doppler velocities, with the yellow/blue couplet indicated the mesocyclone of the storm

We need a way that puts fewer chasers at risk, reduces the potential for chaser-induced traffic jams, and collects more useful information.  An approach that would allow the National Weather Service to get the information they need when storms develop unexpectedly.    And a way to get large amounts of information before severe thunderstorms develop and thus enhance short term (1-12 hr) forecasts.

Could such a breakthrough be possible? 

I believe that answer is emphatically yes.

The approach?  Take advantage of small unmanned aircraft capable of providing both video and weather information while in flight.  And as I will explain below, the planes are ready for action and available from a local company here in the Pacific Northwest.

Imagine you had a small, relatively inexpensive aircraft (costing roughly 50 K$) that had the ability to fly with a high-definition video camera and the same weather instruments in radiosondes (balloon launched weather sensors).  The plane would have a large range (1000s of km) and the ability to stay aloft for extended periods (1-2 days).   A plane that had GPS so an accurate position was known at all times, satellite communication (so it was in constant communication), a sophisticated onboard computer for data collection and flight control, great strength (so severe turbulence would not damage it) and the ability to be easily deployed and recovered.

Such a plane, under the control of National Weather Service staff (or a private firm hired by the NWS) could fly out to potential tornadic storms and fly around funnel clouds or threatening structures (e.g., rotating wall clouds).   Continuous imagery of the developing tornado, with accurate position information, would be available to NWS forecasters, along with insitu observations from the aircraft sensors.   All of this could be done with complete safety and high reliability.     If a new storm developed, such small aircraft could be deployed quickly and, with speeds of 50-100 mph, could get into position quickly and safely (unlike some overly exuberant chasers that drive very fast over rain-slickened roads).    Perhaps you could get an idea of the view of such a small aircraft from the imagery sent back by some TV helicopters during some events (see below).  The imagery could be fed to local TV stations and emergency managers in real time.

 I should stress that it would not be necessary to fly such aircraft into the storm, but just to keep a respectful distance (not unlike the TV helicopters do near some major cities).  The large hail and heavy rime icing in severe convection would not be good for the health of these small aircraft.

Amazingly, an aircraft capable of such unmanned surveillance is now available for purchase from the Aerovel Company of White Salmon, Washington.  Aerovel is a company founded by Dr. Tad McGeer, an extraordinarily talented and innovative aircraft designer, who has created a series of highly successful small Unmanned Aerial Vehicles (UAVs), including many that are now used by our military (e.g., the ScanEagle).   His firm has now developed and successfully tested the Flexrotor, a small aircraft capable of taking off vertically like a helicopter, going into horizontal flight, fly a long mission, and then return to base, landing as a helicopter (see picture).   Go to this web site to see an amazing video of a flight.  A technological triumph.

The current version of this aircraft has amazing capabilities, including a 3,000 km range and an ability to stay aloft for 40 hr, while carrying the instrumentation and video cameras noted above.  It could revolutionize the monitoring of severe storms, and provision of warnings to local residents and businesses.

But the great potential of this aircraft does not end there.   Before storms develop it could fly in the lower portion of the atmosphere (lower few thousand feet) in a way to get voluminous observations of the environment in which convection (thunderstorms) will develop.   Many of us believe that this is an essential ingredient for further progress in severe storm prediction.  In fact, an experiment using manned aircraft (the Mesoscale Predictability Experiment, MPEX) is going on this spring to prove this hypothesis. 

And after severe storms hit, such small aircraft could get extensive imagery of the damaged area to aid first responders and others.

So what stands in the is way of this vision?

First, the National Weather Service needs to consider the potential of such aircraft seriously and funds for the experimental use of the small planes must be found.  Perhaps a local foundation (e.g., Gates, Bezos, Allen) could fund a demonstration project.

Second, the Federal Aviation Administration (FAA) must allow these planes to fly in U.S. airspace.  To put it mildly, the FAA has not  encouraged unmanned aircraft and has severe limitations on this use.  They need to rethink their objections for  UAVs applied for storm forecasting.  Such planes could potentially save many lives.  They will do most of their flying around severe thunderstorms, where few commercial or general aviation flights dare travel.  The planes will be in constant contact with controllers and their positions will be known at all times, so other aviation will be constantly appraised of their position. 

It would be ironic if we could use unmanned aircraft to kill and damage our foreign enemies, but were unable to use them to save many American lives.

Small unmanned aircraft have the potential to revolutionize severe storm prediction and warning, and would give the National Weather Service a powerful tool for protecting American lives and property.  Such UAVs have other potential  meteorological applications, like hurricane reconnaissance.   I believe they are the future, but it will take some effort and vision to make it a reality.