Saturday, September 14, 2019

Two Strong Fronts will Bring Unusual Amounts of September Rainfall

If the model forecasts are correct, this is going to be one of the wettest Septembers in recent memory.  And it is clear: wildfire season is over.

The first act starts tonight as a strong front moves in this evening.  The coastal radar is being overhauled--so I can't show you an ominous radar view.  But the latest infrared satellite image is impressive--particularly for September.


The UW high resolution WRF model 3-h precipitation forecast for 2 AM this morning show the front moving in.  And with the front, winds are going to pick up.

And then as a low pressure area moves towards us on Sunday, the precipitation will blossom, filling much of the state with moderate rain (see 3-h rain ending 2 PM Sunday).  This would be a lot for November.  And extremely wet for east of the Cascades.  


And then ANOTHER unusually strong front moves in on Tuesday (see below)


Now...are you ready to be meteorologically shocked?  Here is the accumulated precipitation total through 5 PM Tuesday.  Amazing.  Big areas of 2-5 inches.  Lots of rain in eastern Washington.


This September is already wetter than normal.   After the next week, the region will be thoroughly soaked.   A good time to plant grass seed or put in some bushes or other plants in the garden.

Thursday, September 12, 2019

President Trump Damages U.S. Weather Prediction--But He Had Help

During the past week, there has been non-stop media coverage of Trump's  problematic foray into weather forecasting.

But what has not been covered is the damage done to NOAA and the future potential of U.S. weather prediction by this incident.  And the potential damage to the careers of some exceptional public servants caught in the undertow.  Or real evaluation of what Trump said about Dorian.

Although Trump, his chief of staff Mick Mulvaney, and his Commerce Secretary Wilbur Ross are prime villains in this story, some of the media, the political world, and even some in my community made the whole situation much worse than it had to be.   There are a lot of subtleties being missed in the public domain--so let me provide my take on it.

Trump works by doing outrageous things, getting lots of attention, provoking an excessive reaction from the other side, which he points to as proof he was right.  And on and on.  All kinds of folks start fighting each other, innocent individuals get hurt, and national interests are undermined.

Trump's Forecast

This unfortunate interlude began with Trump's tweet on Sept. 1st, in which he suggested that South Carolina, North Carolina, Georgia and Alabama would be hit much harder than expected by Dorian.   Now the forecast had changed before his tweet, with the storm moving northward towards the Carolinas.  So he was partially correct.  But what he said about Alabama was wrong-- with the new track Alabama had a sharply reduced threat.


Within 20 minutes of Trump's tweet, the Alabama NWS responded (they are in central time).
They make a strong blanket statement that Dorian would have no impacts on Alabama.  If they had said that there was a high probability that there would be no significant impacts, they would have been in an unassailable position.  But their wording left them open to criticism for two reasons.  

First, the most up to date forecasts on Sunday morning had a slight probability (5-10%) of tropical storm winds  reaching Alabama (see below)

Second, and even more important, as the storm passed there WERE modest impacts on Alabama, with winds gusting to around 25 mph.  Below is the proof, showing the maximum winds on September 5th.  The ovals indicate the areas of gusty winds reaching 25 mph over Alabama (click to enlarge).  And sinking air forced by the storm resulted in several daily temperature record being broken in Alabama.  So the impacts were minor (perhaps a few broken branches), but if one was talking literally, there were impacts of the storm.


And why did the Birmingham NWS forecaster provide a prediction for the entire state when his/her responsibilities were solely for the northern area around Bellingham?  Established NWS protocols were not followed.

You would think that there was not enough "meat on the bone" for this Alabama forecast business to have any traction, but that was not the case.   Many media sources went nuts, with all kinds of stories making fun of Trump.  And how he was undermining weather prediction, etc.  Just a bit too much (see below)


This was revved up even further, when Trump appeared to be unfamiliar with the occurrences of category five hurricanes during recent years (there have been a few):

“I knew it existed, and I’ve seen some Category 4s ― you don’t even see them that much ― but a Category 5 is something that I don’t know that I’ve ever even heard the term other than I know it’s there,” he told reporters.

It is clear that the President is uninformed about hurricanes--and he made a mistake on the Alabama threat.  But the media went into hyper mocking mode and tried to score some points on him...and this President doesn't like to be mocked and went into full defense mode. 

What makes the media reaction so overblown is that no one takes Trump's forecasts seriously, not even the most strident Republicans.  I confirmed this by asking a few enthusiastic Trump supporters.  They love the guy because he is bull in the national china shop--but for weather predictions, they trust the National Weather Service and the National Hurricane Center.

Sharpiegate

The next stage of this sad drama occurred on Wednesday, when President Trump talked about the hurricane and used an OLD National Hurricane Center uncertainty chart (see below).  I mean really old (the previous Thursday).   He was basically saying (correctly) that the previous track took the storm into Florida and the Gulf, but the latest predictions swung the storm north.  What he said was true.  But there was a line going into Alabama on the original map suggesting an extension into the Florida Panhandle and a bit of Alabama.  He never discussed it.


But that unmentioned line cause the media and some others to go wild, claiming he was deceiving the public, illegally altering official NOAA charts, and more.    This reaction was totally excessive and was meant to put Trump on the defensive.

But if someone knew anything about some uncertainty charts, that line was not unreasonable if it refereed to the path of the hurricane at the time the chart was released.   If the storm HAD followed the path shown, the storm might well have gone into Alabama.   In fact, the ensembles of many forecast at that forecast initialization time (Thursday morning, August 29th), DID have trajectories going into Alabama (see below), which Trump actually did mention.  He was right about that.


But now the media was going in full-tilt Trump mocking mode, particularly CNN.  A lot of it was simply unfair.   And their continuous attempts to embarrass him, particularly on the Alabama business, led to something far more serious.

According to the NY Times,  Trump told his Chief of Staff, Mike Mulvaney to have NOAA deal with the situation and particularly to "clarify" or publicly correct the forecasters' position.  Mulvaney then called Wilbur Ross, Commerce Secretary, who in turn telephoned Neil Jacobs, Acting Administrator of NOAA.   The NY Times sources then suggest that Ross told Jacobs to fix the situation, threaten to fire Jacobs and others if something wasn't done.  Ross denies giving such threats.

Neil Jacob's Dilemma

Dr. Neil Jacobs, who is now running NOAA, is a very good scientist and an expert on numerical weather prediction.  He is not political, but extraordinarily dedicated to improving U.S. weather prediction.  He is the change agent that NOAA has needed for a long time.  And I am not saying this in ignorance--I know him quite well and have worked with him for years, including at his previous position as lead weather scientist at Panasonic.  But he is a young man without extensive experience in DC and dealing with its shark-filled political waters.

Neil Jacobs

According to the NY Times, he pushed back on Ross' demands.  But he was under great pressure.  What should he do?  Neil knew that the Trump administrator was supportive of improving U.S. weather prediction (as are legislators on BOTH sides of the aisle).    So should he resign or publicly oppose the President, and jeopardize the potential to enhance weather prediction, which would save lives and property?  Or should he write an innocuous statement that was completely true and one that any real meteorologist would immediately know was meaningless, but would satisfy the weather-ignorant in the Trump administration?

You might disagree with the latter approach, but that is what Neal did--hoping to protect the long-term progress of US weather prediction.   Here is the statement that NOAA released on Friday


Let's examine it.    The first paragraph is completely correct--the National Hurricane Center guidance DID have a chance (admittedly a small one) of tropical storm force winds getting over Alabama.   And the Birmingham NWS forecasters said there would be NO IMPACTS and did not qualify the risks properly (impacts of what?, suggesting the chances were zero % rather than the predicted 5-10%).      Quite honestly, I have been at a number of professional meetings on this very topic, where forecasters are advised to use probabilities more and not to communicate risks as 0 or 100%.

This statement is like a dentist telling you that you did a great job on cleaning your teeth, but forgot to floss one tooth.

So Neil's approach was a clever way of not really criticizing the forecasters seriously but seeming to say something in the minds of the uninitiated.  I smiled when I read it.

OK, perhaps he should have called NWS Director Louis Uccellini and NOAA AOR Head Craig McClean and others to create a pact where they would all stand up to the Trump folks--but such an approach had risks with such an unsteady and unpredictable group in the White House.  What he did was not unreasonable and not unhonorable.  And he is getting severely criticized in some quarters for it....unfairly I believe.

The Knives Come Out

The NOAA statement caused a firestorm, both inside and outside of NOAA with folks suggesting it represented a profound attack on NOAA's independence, of unethical behavior from NOAA leadership, a degradation of NWS forecasters and worse.  Some individuals inside of NOAA, who should have understood the dynamics of the situation and what Neil was trying to do, took out the knives.


Just classic Trump---he stresses an agency or group until the good guys start turning on each other, producing the bedlam that is his hallmark.   And the impacts are profoundly bad for the American people.

On Tuesday, Neil talked to the professional group encompassing many National Weather Service forecasters (the National Weather Association).  Instead of discussing the key innovation he was working on to improve U.S. numerical weather prediction (the EPIC center), he spent his time giving an emotional talk about the importance of forecasters in the National Weather Service.  Everyone listened respectfully and at the end his received polite applause.  But the momentum to make U.S. weather prediction a world leader again has been greatly lessened.

It is time for my community to come together, stop attacking each other about how we deal with Trump, and get back to work making U.S. weather prediction the best in the world.   And I hope that political leadership in both parties will protect people like Neil Jacobs, whose only goal is to serve the American people in such a critical capability for the nation.  The battle between Trump and his opponents is loud and energetic, but NOAA should not be caught in the middle and end up collateral damage.

Tuesday, September 10, 2019

Super Heavy Rain in Everett Causes Flooding

On Monday night, an intense convective cell parked itself over Everett producing very heavy rain, sewer overflows, and flooding that closed some roads and Everett High School.

Steve Link's twitter feed showed some of the action:


How much rain?  During the 11h ending 11 PM Monday, there was about 3 inches (see below)..and much of that fell between 5 and 7:15 PM Monday.  Surrounding areas had a few tenths or less.


Let me show you as series of radar images between roughly 6 PM and 7:15 PM Monday.  Red colors are the really heavy stuff.

 At 5:56 PM, a strong cell was over Everett.


6:08 PM--still there.

6:20--it is pouring over Everett still

7:07 PM--starting to fade.

The visible image at 6:20 PM shows the convective cells:

The tops of these convective cells got to around 21,000 ft...nothing like the massive storms we had on Saturday night (see radar echo top below)--- thus, there was no lightning with them.   They just got locked up for a while over Everett, for reasons I can only speculate on.


Everett could use their version of Seattle RainWatch--a radar-based warming system we developed for Seattle. 

Monday, September 9, 2019

Why So Much Lightning over Western Washington on Saturday Night?

Saturday night was the "perfect storm" of western Washington lightning, producing the best display in 20 years.   There were thousands of lightning strikes between 6 PM and midnight, driven by unusually vigorous thunderstorms.

But why?

Before I answer that question, let me get you into the mood by watching an extraordinary video produced by the master of weather cams, Greg Johnson of Skunk Bay weather.   He has four cams looking northward from his home on the north side of the Kitsap Peninsula.  Stunning amount of lightning was captured by his cams...both cloud to cloud and cloud to ground. Be prepared to be moved....




To get strong thunderstorms, the key requirements are an unstable atmosphere--one that will convect if air parcels are lifted---and something that will push the air parcels upwards until they can rise on their own.   And for Saturday night's thunderstorms, we needed something else as well--winds aloft that would direct the thunderstorms away from their generation points in the Cascades and up Puget Sound.

Extraordinary Instability

A column of air is primed for instability when the temperature decreases rapidly with height, and
with plenty of moisture in the layer near the surface.     A measure of the potential for instability is something called CAPE:  Convective Available Potential Energy.  The values of CAPE forecast over western Washington for Saturday late afternoon and evening were amazing (see below), with CAPE at 5 PM getting to around 1500 J per kg over the Cascades and 700 over Puget Sound.  Around here, we get excited when we get values reaching 100-200.  So the values were very high, very unusual, and signified the potential for strong thunderstorms.


One reason that values were so high was the blob of warm water off our coast.  The  BLOB not only contributed to warmth at the surface but more water vapor--important fuel for instability.   The eastern Pacific sea surface temperature is roughly 5 F above normal and that implies substantially more moisture in the lower atmosphere.  At the same time, an upper level trough was bringing in cooler than normal air above the surface (see map for 500 hPa...roughly 18,000 ft).   So warm, humid air at low levels with cold air aloft.  That means a large change of temperature with height and lots of potential instability.


But as in the late night commercials, WAIT...there's even more!  The approaching upper level trough was associated with upward motion, which help trigger the convection (thunderstorms).   Initially, the focus of the storms were over the Cascades, because the mountains provide more lift and an elevated heat source.

But because the trough was negatively tilted--oriented northwest-southeast--the flow aloft had a southeasterly aspect to it (flow from southeast), which helped the thunderstorms born over the southern Cascades to move over the western lowlands.  This southeasterly flow was evident in the winds above SeaTac Airport as shown below (see blue oval indicates the relevant elevation and time). The heights are in pressure, with 700 about 10,000 ft.  Time is on the x-axis, with 08/03 being 8 PM and time increasing to the right.

So we had the trifecta for Puget Sound thunderstorms:  great instability, a sharp trough aloft given strong lift, and the perfect winds to drift the storms over the lowlands.

To have the combination of all three is quite rare around here. As noted in my earlier blogs, the large instability produced some of the tallest, strongest and most numerous thunderstorms we have seen here in a very long time.  Some tops got to 40,000 ft.

 The ultra-high resolution UW WRF model did an amazingly good job on the forecast.  Here is the simulated infrared 18-h forecast from the highest resolution domain.  It was going for big convective cells over western Washington. Impressive.






Saturday, September 7, 2019

Major Convective Event, with Heavy Rain, Lightning and Thunder, Moving Through Puget Sound

An unusual major lightning/thunder event is occurring over Puget Sound, delaying the UW Husky Game. 

And interestingly, the UW WRF model forecast the event earlier in the day.

The radar at 8:15 PM shows the action, with the red colors being very heavy precipitation within convection.


The view from Husky Stadium was amazing.   Good idea to get folks off the field and out of the stands.
Picture by Peter Benda


The WWLLN lightning network shows extraordinary amounts of lightning over the area.  Here is the lighting totals for the 30 minutes ending 8 PM.   Puget Sound is being pummeled by lightning!

What is really amazing is the large number of power outages associated with the lightning (see below).  Seattle's system is poorly protected from lightning because it is so rare.


The convection is associated with a very sharp upper trough that is making landfall, coupled with some unusually unstable air over western Washington. Here is the upper level (500 hPa) map for 8 PM Saturday...very sharp trough making landfall.



Forecasts were very good.  Here is the high resolution WRF forecast initialized 5 AM this morning showing the 3-h rainfall starting 8 PM.  Impressive.

Update Sunday Morning

Here is the incredible lighting strike map for the 24 h ending 1 AM.   Thousands of lighting strikes with hundreds over Seattle alone.  Amazing.


The tops of the thunderstorms were exceptional for around here, with some reaching 35,000 to 40,000 ft.    Here is an example of the radar echo top at 8:19 PM...the top was 36,000 ft.  Normally, we get excited when tops get to 20,000 ft in western Washington.


Thursday, September 5, 2019

The Eye of Hurricane Dorian Passes Right Over a NOAA Buoy with a Live Webcam

Something extraordinary has happened....a hurricane (Dorian) has passed right over a NOAA/National Weather Service buoy with a cam on board, providing a unique view of what it is like to be in a hurricane at sea.

The location of the buoy (41004) is shown below, with the current location (red dot) and predicted future track of the hurricane shown as well.


The pressure (green line) and wind plots (sustained and gusts) at the buoy are shown below.  You can see how the winds peaked in the eyewall of the hurricane, with gusts as high as 85 knots, and dropped to near zero in the middle of the eye where the pressure was a minimum.  Just amazing.


But now the amazing part....the pictures from the buoy!  Here is one, inside the eyewall at 1810 UTC (click to expand).  Huge waves, like a wall in front of the camera.


One hour earlier, you can see more...with big waves and a huge amount of spray

Looking back to 1610 UTC, when the buoy was in the center of the eye, the scene was bright, the waves were less and birds were flying around. They were trapped.


 If you want to check it out yourself, here is the link

The differences in wave height inside the eye and in the eye wall surprised me.   Here is the plot of significant wave height (average of top 1/3 of waves).  Increased to around 25 ft in the eyewall, follow by a drop to 11 feet in the eye.


 Next buoy to be hit is Frying Pan Shoals where the wave height is currently only 21 feet....and here is the image.  You don't want to be out there.




Wednesday, September 4, 2019

A Junior Blob Off the West Coast--But Still Cool for a Hurricane

The latest plot of the difference of the current sea surface temperature from normal (the SST anomaly) available from NOAA shows that some of the most unusually warm water across the planet is now offshore of the West Coast.   Some of the water is 2.5-4 C degrees warmer than normal (4.5-7.2F warmer than normal).  Since it has only been there a few months, let's call it a junior BLOB.


One reason for the BLOB development has been a persistent areas of high pressure over the eastern Pacific.

Some folks have asked me whether we might get a hurricane like Dorian over the West Coast, particularly since our offshore waters are warming.  A good question.

The answer is no.  Even with a major BLOB off our coast, the sea surface temperatures over the eastern Pacific are still too cold.   Hurricane development requires ocean temperatures of at least 80F (or 26.5F). 

Below is the latest plot of sea surface temperatures around North America provided by NOAA.  Blue/Green is cold.   Red is warm (you could guess that!).  26.5C or 80F is where the color turns from yellow to orange.    The Gulf of Mexico is great for hurricanes, as is the south Atlantic.

But yikes!  The water temperatures off the West Coast even with Ms. Junior BLOB is WAY too cold (around 50F).  No hurricanes for us.   Ever.
If you look carefully at the first picture above, you will notice some blue color off of southern Florida....that is the result of the churning of the upper ocean by Hurricane Dorian, bringing up cold water from below.

To really see this effect, let me show you the sea surface temperatures measured at a buoy that was run over by the storm (buoy 41010, just north of the Bahamas).  Pretty amazing... a cooling from around 85.5 F to 81.3 F.


This cooling of the ocean's surface was enhanced by the halting of the storm's motion over the Bahamas (so the storm was stuck over cooling water), and led to the storm weakening rapidly from a category 5 to a category 2 storm.

Announcement:  I will be giving a talk "The Great Storms of the Pacific Coast" in Ocean Shores at 6:30 PM on September 7th at the Shilo Inn as part of the Coastal Interpretative Center's summer lecture series.  More information is found here: https://www.interpretivecenter.org/.   Shilo Inn is offering special room rates for those wishing to stay overnight, as well as a special buffet.   

Monday, September 2, 2019

Hurricane Dorian is a VERY Small Storm That is Moving Very Slowly

There has been a  lot of coverage in the media about Hurricane Dorian, but most have not been stressed how SMALL the storm is.   And size matters, limiting the damage to the immediate vicinity of the center of the storm.  A recent image from the Miami radar shows the storm about 120 miles offshore, with a small eye and circling eyewall rain bands.


According to the National Hurricane Center, hurricane-force winds (64 knots or more) extended only 45 miles from the center--the diameter of hurricane winds was only 90 miles.

Compare that to Hurricane Irma, which hit Florida in 2017--it has a diameter of 420 miles ifor the hurricane winds!  Hurricane Sandy in 2012 had a hurricane-force wind diameter of 1000 miles at one point.

The small size of Dorian is shown by the wind forecast for 5 AM PDT Tuesday morning-- the hurricane force winds (purple colors) stay way offshore and don't reach the Florida mainland.


The maximum gusts today (see figure) show gusty, but modest, winds of 30-40 mph along the eastern coast of Florida.  Makes sense considering the small diameter of the storm.


Dorian has essentially not moved during the past 24-hours, keeping the strong winds over the Bahamas, where terrible damage is occurring.  But the small size has another benefit... it limits the growth of large waves, which increase with fetch--the distance over which strong winds work on the water.  This is illustrated by the wave prediction for 3 PM PDT Monday afternoon from the NWS WaveWatchIII system.  Small area of large waves, with none larger than 10 meters.

Staying in one place is bad for a hurricane.   Hurricanes depend on warm water and they churn up the ocean, bringing cooler water from below.  If the hurricane doesn't move it will weaken...and Dorian has already declined from a category 5 to 3 storm.   A NOAA buoy in front of the storm illustrates the cooling.

The latest forecasts are for the storm to slowly move north-northwestward on Tuesday, with the storm gradually increasing in size.  To illustrate,  here is the NOAA/NWS HWRF forecasts (their high-resolution hurricane model), showing some increase in size, with hurricane strength winds just offshore of the coastline.  Really close.  


 Florida will probably escape serious damage from Dorian, but the show is not over, as the storm expands in size, speeds up, and then makes a grazing landfall on North Carolina.