A Super Radar Explained on Super Sunday

If you were using the NWS’s estimate of Kansas rainfall Friday morning, after two lines of strong thunderstorms moved through, you would be tempted to issue strongly-worded flash flood warnings as the estimate was that as much as ten inches of rain had fallen over a very large area about 40 mi. WSW of Wichita. Streams would have been rising rapidly and roads closed.

Only one problem: The actual rainfall was 2 to 3.3″, substantial yes, but not enough to cause flooding given the recent very dry conditions.

The erroneous rainfall estimates were caused by “hail contamination” — where the radar senses the very high reflectivity from wet hail and mistakenly computes and totals it as rain resulting in a wild overestimate.

On this blog and elsewhere the past year, weather fans and others have heard a lot about dual-polarization (DP) radar. DP, when perfected, will solve this problem and many others.

As you know, the NWS is installing dual-polarization radar across the U.S. An easy to understand explanation of dual polarization radar is below, featuring the lovely and talented Cat Taylor.

When perfected, D-P will allow better warnings of tornadoes, flash floods, and heavy snow. Below is an example from 9:50pm Thursday evening showing large hail (red) inside a northern Oklahoma severe thunderstorm warning polygon as it moved northeast. The storm produced hail at least 1.5″ in diameter. DP nailed it! The hail is clearly differentiated from the heavy rain (dark green).

You can see that the actual area of hail in red (this is the same storm that moved into Kansas and caused the hail contamination shown in the uppermost image) versus the areas of rain. Instead of estimating what is rain and what is hail, this radar measures them.

This is still a powerful tool that we don’t yet fully understand. The same was true of Doppler radar in the ’90′s. It took us time and trial and error to sort out everything it can do. Now, Doppler allows is to issue much more accurate and timely warnings of tornadoes and damaging winds.

The next few years of working with DP promise to be very fruitful and represent yet another step forward in the improvement of warnings of extreme weather.

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Christmas Tornado Down Under

A tornado occurred on Christmas near Melbourne, Australia, with damage reported. Attached is a radar image of the supercell and hook echo (arrow). As would be expected in the Southern Hemisphere, the hook is on the northwest side of the supercell.

Click to enlarge. Hat tip: Michael Thompson.

Weather Radar Interpretation: Wave Clutter

When viewing weather radar, people are used to seeing “ground clutter” — the radar beam’s energy striking the ground or buildings or other features and scattering some of the energy back to the radar. But what are the echoes south of the Island of Kauai?

Answer: Wave clutter.

Just like the earth is not flat, often neither is the ocean. In the case the radar’s energy (red) strikes the tall wave and part of it (purple) reflects back to the radar. It is displayed as wave clutter. Of course, in nearly calm seas there is little, if any, clutter from waves.

How Is the Rain Storm Coming?

Here is the radar at 9:10am CDT. More than four inches of rain have fallen so far in west central Kansas. That is snow around Colorado Springs.

Below is an experimental radar forecast valid at 6pm this evening.  If you are going to football games in the region, prepare accordingly. In addition, there could be some lightning delays.

Gonna Be Tough to Get the Game In

Update 10:29pm EDT: Game postponed to 8:37pm Saturday. Will resume in second inning. 

Here is the radar as of 10:07pm EDT. Yankee Stadium is the blue circle and the red arrow is the direction of movement of the storms.

Good Work, Senator Cantwell

This one slipped past me when it was first announced. I’ll let her take the deserved credit:

SEATTLE, WA –U.S. Senator Maria Cantwell (D-WA) announced that Washington state’s first coastal Doppler radar, located in Grays Harbor county, has been plugged in for the first time and is now sending test weather data to the National Weather Service’s Weather Forecast Offices located in Seattle and Portland. The state-of-the-art Doppler radar is undergoing testing this month and then will be one of the first in the nation to be upgraded with the latest enhancement to radar technology in civilian weather forecasting, called dual polarization. 
“With Washington state’s first coastal Doppler radar now online for testing, we are on the final home stretch to improved detection and monitoring of storms over southwest Washington,” said Senator Cantwell. “Too often in the past, our weather radar coverage gap meant that forecasters didn’t have the most complete data set possible to help Pacific Northwest communities prepare for big storms. This new, state-of-the-art radar technology will enable Washingtonians to better prepare for the impact of the big Pacific storms on businesses and homes.”
Western Washington’s only other Doppler radar is located on Camano Island, but the radar’s reach is largely blocked by the Olympic Mountains, causing large gaps in weather data of storms approaching the Washington coast. The new coastal radar will help close this data gap, enabling forecasters to better determine wind speed and rainfall of incoming storms to give more accurate and timely warnings to residents in harm’s way and help prevent loss of life and billions of dollars in property damage.
New western Washington Doppler radar
Here is data from the new radar:

Twofer Tornadoes

Immediately below is a posting about the tornado watch for northern Oklahoma and southern Kansas that was in effect yesterday afternoon and evening. Were there any tornadoes? Yes. In fact, we had a twofer: Two tornadoes going on at the same time from the same storm.

The video below (hat tip: Accuweather.com) shows a rope tornado at the right and a more conventional cone-shaped tornado at the left.

Here is what the radar looked like as the tornadoes were developing.

For weather fans: We know that the RFD is important to tornado formation. It is infrequent that radar shows the “rear flank downdraft” (blue arrow) and its position relative to the hook.

As far as I know, neither tornado did any damage.

ADDITION: Friend Jim Reed captured the tornado on the left. You can see his photos here.

Sometimes Good Can Come from Natural Disasters

Yet when describing what is commonly known as the Andover tornado, two prominent weather officials often use an unlikely word: lifesaver.

The tornado struck while a new radar system was being field-tested, and the radar performed so well that instead of being canceled it was approved for production, officials say.



It is hard to image that good can come from a major tornado. But, twenty years ago, the Andover tornado of April 21, directly led to the installation of the Doppler radar network that may have saved lives as recently as this afternoon in Georgia.

The story from the Wichita Eagle

We Don’t Know What We Don’t Know

Most of the High Plains Conference this afternoon was devoted to the new dual-polarization (DP) radars. In theory, the DP’s should produce much more accurate estimates of the amount of rain falling. So far, in very limited testing, they have not. We have some ideas as to why that is the case and we think it can be fixed.

When doing scientific research and technology development it is common to run into unexpected obstacles. That is why it is research. This one has caught me by surprise and I’ll blog from time to time as we learn more.

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Thunderstorms in the Summer Heat

Thunderstorms have developed in southern Kansas. In the heat, the storms, which are near Cheney Lake, produced a small microburst at about 8:18pm. The image below is from the Wichita Terminal Doppler Weather Radar and the greens are winds toward the radar (blowing from northwest to southeast) and the orange are winds blowing away from the radar (southeast toward the northwest).

The microburst is likely associated with this rainshaft (enlarged from above photo):

And, here is the conventional radar image of the storm.

How Do We Track a Massachusetts Tornado? With the Same Techniques We Use in Kansas

Already today, I have seen one comment that the Massachusetts tornado was “unpredictable.” While this has been a horrible tornado season (worst in more than a half century), the tornadoes have been extremely well predicted.

That said, I have also received a number of questions about how the long-track Massachusetts tornado was forecast and tracked and I’m happy to answer them. The graphic below was posted on this blog the evening before the tornado. Western Massachusetts is in the 30% relative probability area for tornadoes and severe thunderstorms which is a high number for the day before an event.

The graphic below was posted on my AccuWeather Pro blog (where I go into the deeper meteorology than I do in this public blog) about three hours before the tornado formed. I call the probability of tornadoes “very high.” The oval was where I was forecasting the high tornado risk. A tornado watch was issued for the public about twenty minutes later.

The tornado’s formation, from a “supercell” thunderstorm, evolved as it would in a Kansas tornado. Here is the radar at the touchdown point of West Springfield complete with “debris ball” (circled) which is a signature of a tornado on the ground.

The radar’s Doppler wind display was very helpful throughout the afternoon showing the tremendous value the public has received from the National Weather Service’s investment in Doppler radar in the 1990′s.

The rotation track of the Massachusetts tornado. The radar, south of Boston,
showed high-speed winds away from the radar (pink) next to high-speed
winds toward the radar (curved arrows). I have marked the
previous centers of rotation. There was even a “hail spike” indicating
the very large hail that fell with this storm. 

The last well-defined debris ball was east of Fiskdale at 5:18pm EDT.

AccuWeather’s SkyGuard® meteorologists were tracking the tornado and informing clients throughout the afternoon. The National Weather Service issued warnings for the public, a number of which were the topic of special reports at AccuWeather.com and on this blog.

Not only did we use “Kansas” techniques on this tornado, a friend of mine from Wichita was vacationing with his family in Boston while this was going on. He wrote,

Thanks, Mike. As luck would have it, we passed on a side trip to Sturbridge and are somewhat north of the primary storm. Glad I looked in on your blog and moved my family out of harm’s way…

In June, 1953, before a tornado warning program existed in the U.S., a tornado struck Worcester, MA killing 94. It is likely that yesterday’s forecasts and warnings kept the death toll (tragically, four) lower than it otherwise would have been.

Tornado Threat Middle Atlantic States

While certainly not a threat of the magnitude of April’s there is a chance of tornadoes from Virginia to southern New York later today.  Current AccuWeather radar shows thunderstorms to the west of the threat area that should intensify late this afternoon.

Keep an eye out in these areas.

A Comment Worth Sharing

This was posted in the comments attached to my posting about last week’s Vilonia, Arkansas, tornado.

Teriann Shrum said…
The pinpoint warning of this horrific storm and it’s 40 minute gateway for warning viewers of it’s arrival is what saved our lives. The image as shown is the Black Oak Ranch Estates community that is 5 miles southwest of Vilonia. Accurate pinpointing of this storm gave us time to seek shelter from it and survive. Out of 120 homes, 16 still stand. We lost 4 members of our community and it could have been many more. THANK YOU for the excellent coverage received from KTHV’s Chief Meteorologist Ed Buckner that saved our lives and the lives of my family! The devastation was “pure hell” for all of us.

Teriann was doing one of the things I hoped would happen when I wrote Warnings: That meteorologists would start to get some of the credit for their lifesaving work. So, way to go Ed!

I also want to mention the incredible work by James Spann in Birmingham during last week’s historic tornado outbreak and the one ten days before.

And, it is not just the TV meteorologists, it is the entire profession that built the technology and discovered the underlying science. Teriann had seen this posting — done the night of the tornado — that showed the tornado before it got to Vilonia. The tornado was moving northeast at 60 mph — a mile a minute — but because of Doppler this non-standard tornado had excellent warning.

Click to enlarge radar images.

Debris ball (left) and Doppler couplet (right) of the violent tornado before it reached Vilonia (circled, at left).

Without this technology and dedication of these meteorologists, the death toll in April would have been in the thousands.

More Meteorological Progress

Kathleen and I were awakened by flashes of lightning and the sound of thunder about 5am — most welcome given the very dry conditions of the last six months.

From time to time, I’ve shown you the National Weather Service’s new experimental forecasts of what the radar will look like in the future. At left is the AccuWeather radar at 5:10am. At right is the forecast made at 7pm last night for 5am this morning.  Perfect? No. But, pretty good.

We continue to make great progress in the field of storm warnings. That progress may be important later today as more severe weather is expected. I’ll have an update on that around 8:30am.  UPDATE posted, see above.

Great Weather Viewing in the Great Plains

I took this photo about 4:40 looking southeast from Wichita. It is of thunderstorms more than 100 miles away in Oklahoma.

Here is what they looked on radar at the same time.

The arrows on the picture correspond right to left to the arrows on the radar image on the latter is left to right.

Update on Alabama Tornado Situation

Radar at 2:58pm CDT. Two new tornado reports in the last 15 min. confirming damage (lower left part of screen).  These storms are moving ENE in the general direction of Birmingham, Taladega and Tuscaloosa. PLEASE take cover if you are in the path of these storms!

Just got a report the tornado sirens are going off in Meridian, Miss. See postings below pertaining to Mississippi.

Long-Track Tornadoes in Mississippi?

AccuWeather SmartWarn® image

The above image was captured at 2:29pm and is of the same two hook echoes as below. There may be two large, long-track tornadoes in progress in Mississippi. People in these areas should take cover. The red polygons are tornado warnings. The burnt orange color in the background is the tornado watch.

For updated coverage, this link will take you to the top of the blog.