Wednesday, October 7, 2015

Hurricane Oho is Heading Towards the Northwest U.S.

Hurricane Oho, now located northeast of Hawaii, is now heading towards the northeast, making landfall on the British Columbia Coast on Friday.  The latest track from the NOAA Central Pacific Hurricane Center has it passing offshore of the Washington coast late Thursday (see graphic)

As a result, the probabilities of of winds getting to 58 mph (shown below) are only high offshore. But even here in Washington State there will be some minor impacts (see below).

A visible satellite image from NASA MODIS satellite on Wednesday afternoon shows that Oho no longer possesses a distinct eye and does not have the symmetric look of a strong hurricane.

One impact from Oho will be waves that will propagate to our coast as long period swell.  Here is a prediction from the NOAA Wavewatch III model for early Saturday morning. The yellows are 8 meter waves...around 25 ft.    This swell will reach the WA coast on Saturday possibly causing beach erosion and dangerous breaking waves.

Let's look at the latest forecasts from the UW WRF system.  This and subsequent plots will show heights (or equivalently pressure) and temperature around 5000 ft (850 hPa).  At 5 PM today, the hurricane was still surrounded by warm air (red colors), with a well defined low center in the middle of the storm.  Still tropical.

By tomorrow (Thursda) at 2 PM, the storm moves northeastward, roughly due west of the OR/CA border.  The structure has changed, with the low turning into a trough and cooler air approaching the storm.  Oho is undergoing what is called extratropical transition, transforming from a tropical to midlatitude storm.

Twelve hours late (2 AM Saturday), the storm had reach the waters of the central WA Coast.  Cooler air is getting entrained into the system, which is looking very asymmetric--like most midlatitude cyclones.  During extratropical transition the energy source of the storm changes, from the warmth of the ocean and the latent heat of water vapor, to the energy inherent in horizontal temperature contrasts.

A key reason why Hurricanes such as Oho undergo weakening and extratropical transition is that fact they pass over cooler water as they move northward.  Generally, hurricanes need water of at least 27C to maintain themselves as a tropical storm.  Take a look at the sea surface temperature distribution in the Pacific, with the route of Oho overlaid.  Oho is now over far too cold water (08/1800 is 11 AM Thursday) to remain a tropical fact, it is now officially a POST-TROPICAL CYCLONE.

How strong might the winds get offshore?  Here is the forecast for the surface wind gusts at 2 AM Saturday.  Lots of gusts above 60 knots over north Vancouver Is and the offshore waters.   It is good this storm is taking an offshore track!

Locally, it could get windy along the coast and over NW Washington, but nothing serious.   If you were thinking of taking a Friday departure for an Alaska cruise, you might rethink your plans.

Carbon Tax Initiative:  I 732

I-732 is now on the final stretch in getting signatures to put a revenue-neutral carbon tax in front of the state legislature.  I strongly support the initiative and I hope you will as well.  CarbonWashington need signatures and financial support.   Places you can go to sign are found here.

Tuesday, October 6, 2015

Apple Computer Could Revolutionize Weather Forecasting: Will It Take the Challenge?

A number of popular smartphones have atmospheric pressure sensors; in fact, there may be a billion smartphones with highly capable atmospheric pressure sensors by the end of 2016. 

Pressure is the most valuable surface observation for weather prediction since it provides information about the the deep atmosphere above.  With pressure alone, meteorologists can determine the three-dimensional structures of the atmosphere.  And pressure does not have exposure problems like wind or a building, in a pocket, inside or outside, in the sun or doesn't make much of a difference where the smartphone is located.  It is the golden parameter.  And meteorologists can make use of both pressure and pressure change to help start (or initialize) our weather forecasting models.

Imagine a world with a billion barometers

So we should get ready for a weather prediction revolution?  Perhaps, but there is a major hurdle that must be crossed first:

The infrastructure for collecting this hugely promising weather data does not exist. 

But at least one company has the potential to radically improve the situation: Apple Computer.

The question is whether Apple will help.

The iPhone 6 series (iPhone 6, 6+, 6S) have now sold over 150 million units around the world and remains the most popular smartphone in many markets.  All have atmospheric pressure sensors.
 By next year, 250 million iPhone 6's will be in use around the world.

To be useful, the pressure from the smartphone must be accompanied by position data from the unit's GPS.  The history of movement of the phone would be help, as would its speed, which would tell us if it were in a moving vehicle.

Apple could assist in a number of ways in the collecting smartphone pressure data.  Obviously, the best approach would be to build pressure collection into the operating system (iOS, which Apple control).  Or pressure collection could be an option in the weather app that Apple preinstalls on every iPhone.

Want to see a shadow of what is possible?  The Weather Channel app allows the collection of smartphone pressure and we were able to get a sample of their data---perhaps we are getting data from 1/1000 of the iPhone6s out there.  Want to see what it gives us?

Let's start with a data rich country...the U.S.  On the left are the convention observation locations over the Oklahoma area, on the right, from smartphones.   Big enhancements You can even get pressures from smartphones on roads.

But the biggest advances might be in second and third world countries without a lot of weather data, such a India.  Below is an image with conventional data on the left and smartphones on the right. Big enhancement.  Many folks have smartphones in developing countries.

Smartphone pressures are also available from some Android phones (e.g., Samsung Galaxy series)--still waiting for a positive response from Google on my inquiries for help in pressure collection.

I have two graduate students working on the use of smartphone pressures for improvement of numerical weather prediction.  We have some initially favorable results with a low density of pressure available from two small companies (Cumulunimbus Inc. and OpenSignal), but we really need more density to prove the value of the technology.

Where might dense pressures really help?   We believe that large numbers of pressure might help forecast the initiation of thunderstorms.   Or provide better short-term forecasts for wind turbines. Situations in which defining small scale weather features are important.  And those are only a few of the potential weather features situation where smartphone pressures might help.

So Apple computer, please give me a call or email.  Or leave a comment on this blog.   You could potentially change the world of weather forecasting at little cost.

Sunday, October 4, 2015

Puget Sound Winter Air Quality Has Greatly Improved

These days there is a lot of talk about environmental problems, but there is one great success story we should not forgot: the substantial improvement in air quality around the nation, and specifically here in the Puget Sound region.

Here is a plot of the levels of small particles (PM2.5, smaller than 2.5 microns), capable of moving deep into the lungs, at Kent, Washington (provided to me by Nick Bond, state climatologist) from 1990 to now during the winter.  You will note a big drop during the 1990s, with levels now a quarter of what they had been.
What about larger particles at Kent (PM 10)?  Major decreases!

Want to know about Seattle?  Huge drops in PM10 (see below).  The red lines shows the warming level of the national air quality standards.   Seattle exceeded in in the late 80s and early 90s.  Now we are well below.

Live in Tacoma?  Big improvements there as well.

Or consider the number of days of moderate or worse air quality over King County:  a big decline in the 1990s

I could show you many more statistics, but you get the picture: the concentration of small particles has radically lessened in our region.  A boon to the health of Puget Sound residents, particularly those that are sensitive to poor air quality.

So why has air quality gotten better?  There are many reasons.

Probably the most important is the reduction in wood burning by our local residents and better wood stoves.   We are simply burning less wood and fireplaces and wood stoves have been a huge source of particles and toxics.

Back in the 80s, the Seattle Times was FULL of ads for wood stoves.   Many new homes had wood fireplaces.   The situation is very different today.  The ads are gone.  Wood burning is less popular, and many homes have gas fireplaces.   Just as important, Federal and local regulations have required that new wood stoves are far less polluting.

A lot of credit should be given to local  and Federal air quality agencies such as Puget Sound Clean Air Agency (PSCAA), the State Dept. of Ecology, and EPA, who have worked aggressively to reduce emissions.   Only low-emission wood stoves are now sold as result of their actions.  When the meteorology is poor for dispersion of pollutants (weak winds, strong and low level inversion), agencies such as PSCAA call burn bans that restrict burning wood other than for primary heating.

Local, state, and Federal  agencies have also worked to reduce emissions from cars, trucks, and large vessels, in addition to lessening emissions from industrial sources.

Getting back to wood.  In general, it is a very dirty and polluting way to heat a home (see graphic from PSCAA).   Natural gas is hugely better and inexpensive natural gas has encouraged folks to use this fuel.

Meteorologically, we are now moving into the worst air quality season for home fireplace/stove smoke.   Nights are getting longer and cooler, so folks want to get the wood burning.  But this is also the season of strongest, low-level inversions, as relatively clear skies allow the surface to radiate heat to space, producing an inversion---warming of air with height.   Inversions are very stable and tend to act as atmospheric caps that keep pollutants, like smoke, near the surface.  Winds are also relative light this time of year, before the big storms approach.

Want a good example of a low-level inversion?   Consider this morning!  Here is the temperature plots with height at the Sand Point (Seattle) vertical profiler, run by the Puget Sound Clean Air Agency.  Large increase in temperature with height in the lowest several hundred meters of the atmosphere.  Pollutants will be trapped near the surface.  And air quality has declined at some locations around the Puget Sound region.
Some folks in rural neighborhoods love burning wood.   But during inversion situations, they end of seriously polluting their own air and that of their neighbors.  I can't tell you how many times I have seen situations like this, with dense smoke coming out of a fireplace that does not loft because of an inversion.  Not good.

The worst wood smoke air quality tends to be in valleys, where the smoke and low-level cool air below the inversion tends to pool.   Some of the low areas of Lake Forest Park, north of Seattle, are notorious.  What is happening there this morning with the strong inversion?  (see graphic of small particle levels).  Oh oh....bad news.  A spike in particle concentrations.

So the bottom line is that regional air quality has greatly improved, particularly in reducing small particle pollution.   But wood smoke is still a serious issue, particularly during inversion conditions and in valley areas.

Friday, October 2, 2015

Extraordinary Flooding Possible In South Carolina

Although I generally keep my view on Pacific Northwest weather, the forecasts for South Carolina and vicinity are so unusual and threatening that I wanted to mention it. And because of Boeing, there are concerns about what happens around Charleston, SC.

Huge rainfall totals are forecast to hit that region, with 10-20 inches being expected in some locations.  Flooding should be expected.

This flooding is NOT directly associated with Hurricane Joaquin, but with the confluence of tropical moisture streams.

Let me begin by showing you the cumulative rainfall totals from the National Weather Service GFS model for the next 66 hours. Over Washington State, some very light precipitation (mainly tonight), but over the eastern U.S. it is the end of the world.   You can see one area of heavy precipitation offshore, with values between 5 and 10 inches....that is the precipitation accompanying Joaquin.   But there is another, even HEAVIER precipitation region with values getting to 15-20 inches stretching from South Carolina and into western North Carolina.  That is what I am talking about.   And this is from a relatively coarse global model--local rainfall could be much heavier.

The NWS Storm Prediction Center three-day forecast totals parallel the GFS runs, giving a conservative total of 13.2 inches.

What I showed you  above was the precipitation totals over several days.   The area of heavy rainfall is associated with a narrow band of precipitation that is forecast to be  extraordinarily persistent and nearly stationary, as illustrated by the precipitation forecast for a 3-h period ending 5 PM PDT tomorrow (Saturday).  You can see the hurricane offshore.

So why does this narrow feature exist?   Substantial insights can be derived from looking at the winds near 10,000 ft (700 hPa), relative humidity, and upward motion at the same time (see map).  There is an area of high pressure to the north (H shown in red) and a low to the south (L in red).  Between them there is a region of strong easterly winds that are bringing moisture into the region.  Moisture that is forced to rise by the nearby Appalachians and their eastern foothills.   But there is more.

Some flow is circling around the low and converging into the easterly flow--right over south Carolina.  Converging air flows cause upward motion that produces precipitation.  But there is still more.  This converging flow is forced to rise by the mountains. The red lines shows upward motion (very subtle but look close and you will see it over S. Carolina).  That upward motion in the presence of tropical moisture is producing intense precipitation.

The latest (9 PM PDT) NWS radar image shows heavy precipitation moving into the area.

The National Weather Service has flood watches, flood warnings, flash flood warnings, and more posted right now (see graphic), and some areas are being evacuated. This is a serious, unusual, and life-threatening event, one that our models have been warning about for several days.  I hope the Charleston Boeing facility is ready for intense rainfall...they are going to get it.

Wednesday, September 30, 2015

Will Hurricane Joaquin Be This Year's Superstorm Sandy?

Superstorm Sandy struck the NY metropolitan area during the last week of October 2012, result in 233 deaths and 75 billion dollars in damage.

The forecast problem today regarding Hurricane Joaquin is extraordinarily similar to the one faced by meteorologists during the week before Sandy made landfall.  Amazingly similar but with an interesting twist.  

Hurricane Joaquin at 8 PM Wednesday

Just as with Sandy, one major forecast model is bringing the hurricane inland with a "left hook" while the other is taking the storm out to sea.  But in this case, the situation is reversed....the  latest (Wed evening) U.S. GFS model is taking the storm inland over New York with heavy precipitation and strong winds.  In contrast, the usually (but not always) superior ECMWF model is pushing the storm out to sea.

Let's look at the latest forecast, starting with the U.S. GFS model (lines are isobars of constant pressure and shading is precipitation).   One can hardly believe one's eyes:  New York/New Jersey is in the crosshairs.  

But before New Yorkers panic, I should note there is a great deal of uncertainty in this forecast.  The previous runs of the GFS model took the storm into North Carolina and Virgina, so the modeling system has not stabilized on a solution.  Furthermore, the GFS model ensemble system (GEFS), in which the model is run many times with different initial conditions, is producing a wide variety of tracks and intensities.   Here is the 90h forecast of GEFS (previous run at 1800 UTC today), presented with what is known as a spaghetti diagram, with each lines representing the 984 hPa isobar (line of constant pressure).  You see the circles all over the place and of different sizes?  That means a lot of uncertainty.

The GFS and GEFS are run at relatively coarse resolution (13 km and 50 km grid spacing, respectively).  The National Weather Service has its high-resolution HWRF model (4km grid spacing) that cost tens of millions of dollars to develop....what does it show? (see below).  Interesting, HWRF is going further south of the main GFS model.

Now lets turn to the supposed Gold Standard weather forecast model, the European Center Model (ECMWF).  The European Center model takes the storm northward and then out to sea towards the northeast, as shown by the following forecasts initialized at 1200 UTC today (Sept 30th).

Saturday at 5 PM PDT
 Monday at 8 PM
 Tuesday at 11 AM PDT

There is substantial uncertainty with the ECMWF forecast, something we can explore by looking at the output of their ensemble system.  Here is their high-resolution forecast (solid lines, isobars of constant pressure) and variability in their ensemble (shaded colors) for 1200 UTC on Monday (5 AM PDT).  The shading to the left of the high resolution low center suggests that some of the forecast took the low farther to the west.

The National Hurricane Center puts out a subjective forecast based on looking at all the models, tempered by human experience.  Their solution?  Take the hurricane up the coast over DC.  This would shake things loose in the nation's capital....maybe encourage the purchase of a better weather supercomputer!

And one thing that is pretty sure-- no matter what happens:  the East Coast will be hit by heavy rain.   Here is the cumulative precipitation through Tuesday at 5 PM.  Five to 15 inches along the coast.

So what should you take away from all this?

A dangerous hurricane is moving northward but the track of the storm is still highly uncertain.  Major international modeling systems disagree.  Their ensemble systems (many forecasts run with slightly different initial states) disagree.  Consider the trending of the GFS model farther northward each run and the stability of the EC solution, I suspect the storm will track into New England or just offshore, but it is impossible to be sure at this point.  HWRF seems to be going the wrong way (too far south).

Folks should not panic, but those from Cape Hatteras to Boston should watch the forecasts carefully and begin preparations.  Hopefully, the models will converge during the next day to a robust solution.

Monday, September 28, 2015

A Perfect Autumn Week

I know many of you are looking forward to rain and clouds, but they will come soon enough.

In the meantime, enjoy an extraordinary fall week, with temperatures getting around 70F, no rain, and lots of sun.  And the bite of crisp temperatures in the morning to ensure you feel invigorated and alive.

The temperatures during the past four weeks have been very close to normal, as shown by the plot below (red and blue lines are average highs and lows)
Precipitation has been a bit below normal during the same period (blue is normal, red observed), by roughly .7 inches.
Want to see something amazing?  Here is the total precipitation predicted though Saturday at 5 AM (from the GFS model)  Nothing along the U.S. West Coast-:  WA is entirely dry.   But the  East Coast gets washed away.  SE Alaska gets torrential rain as well.

The pattern producing this weather is really not exceptional (see upper level map below for tomorrow afternoon).  A deep trough over the Gulf of Alaska is trenching Alaska, while a weak ridge is stationed over the western U.S. and Canada.  A weak trough is off of our coast.

The National Weather Service forecast for the next four days is  as close to ideal as imaginable (see below), with highs around 70 and lows near 50 (colder away from water). Sun.  No rain.

Last night some of the cooler suburbs southeast of Seattle dropped into the mid-30s...and that was at 2-m above the surface.  Some folks surely had frost.  In contrast, the temperatures only dropped to the mid-50s at some locations near the water. (the 92 was probably a thermometer near someones grill).  I am always amazed by our local contrast on cold, clear nights.  20F differences is not unusual...can get to 30-35F in the right situations.

This good weather won't last forever.  The latest NAEFS North American ensemble forecast of many model predictions indicates more clouds and some rain by the second week of October (see below).   So enjoy this pattern while you can.