Wunderground launches high-definition radar product

By: Dr. Jeff Masters , 2:46 PM GMT on December 15, 2008

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The Terminal Doppler Weather Radar (TDWR) is an advanced technology weather radar deployed near 45 of the larger airports in the U.S. The radars were developed and deployed by the Federal Aviation Administration (FAA) beginning in 1994, as a response to several disastrous jetliner crashes in the 1970s and 1980s caused by strong thunderstorm winds. The crashes occurred because of wind shear--a sudden change in wind speed and direction. Wind shear is common in thunderstorms, due to a downward rush of air called a microburst or downburst. The TDWRs can detect such dangerous wind shear conditions, and have been instrumental in enhancing aviation safety in the U.S. over the past 15 years. The TDWRs also measure the same quantities as our familiar network of 148 NEXRAD WSR-88D Doppler radars--precipitation intensity, winds, rainfall rate, echo tops, etc. However, the newer Terminal Doppler Weather Radars are higher resolution, and can "see" details in much finer detail close to the radar. This high-resolution data has generally not been available to the public until now. Thanks to a collaboration between the National Weather Service (NWS) and the FAA, the data for all 45 TDWRs will be made available in real time over the next few months via a free satellite broadcast (NOAAPORT). Six radar sites are already available (Figure 1), and the remaining radars will be added by June 2009. I'm pleased to announce that the Weather Underground is now making the TDWR data available to the public, and will be adding new sites as they become available. We're calling them "High-Def" stations on our NEXRAD radar page. The six TDWR sites available so far are:

Detroit, MI
Cleveland, OH
Fort Lauderdale, FL
Miami, FL
West Palm Beach, FL
Newark, NJ

Since thunderstorms are uncommon along the West Coast and Northwest U.S., there are no TDWRs in California, Oregon, Washington, Montana, or Idaho.


Figure 1. The network of 45 Terminal Doppler Weather Radar (TDWR) stations in the U.S.

Summary of the TDWR products
The TDWR products are very similar to those available for the traditional WSR-88D NEXRAD sites. There is the standard radar reflectivity image, available at each of three different tilt angles of the radar, plus Doppler velocity of the winds in precipitation areas. There are 16 colors assigned to the short range reflectivity data (same as the WSR-88Ds), but 256 colors assigned to the long range reflectivity data and all of the velocity data. Thus, you will see up to 16 times as many colors in these displays versus the corresponding WSR-88D display, giving much higher detail of storm features. The TDWRs also have storm total precipitation available in the standard 16 colors like the WSR-88D has, or in 256 colors (the new "Digital Precipitation" product). Note, however, that the TDWR rainfall products generally underestimate precipitation, due to attenuation problems (see below). The TDWRs also have such derived products as echo height, vertically integrated liquid water, and VAD winds. These are computed using the same algorithms as the WSR-88Ds use, and thus have no improvement in resolution.

Improved horizontal resolution of TDWRs
The TDWR is designed to operate at short range, near the airport of interest, and has a limited area of high-resolution coverage--just 48 nm, compared to the 124 nm of the conventional WSR-88Ds. The WSR-88Ds use a 10 cm radar wavelength, but the TDWRs use a much shorter 5 cm wavelength. This shorter wavelength allow the TDWRs to see details as small as 150 meters along the beam, at the radar's regular range of 48 nm. This is nearly twice the resolution of the NEXRAD WSR-88D radars, which see details as small as 250 meters at their close range (out to 124 nm). At longer ranges (48 to 225 nm), the TDWRs have a resolution of 300 meters--more than three times better than the 1000 meter resolution WSR-88Ds have at their long range (124 to 248 nm). The angular (azimuth) resolution of the TDWR is nearly twice what is available in the WSR-88D. Each radial in the TDWR has a beam width of 0.55 degrees. The average beam width for the WSR-88D is 0.95 degrees. At distances within 48 nm of the TDWR, these radars can pick out the detailed structure of tornadoes and other important weather features (Figure 2). Extra detail can also been seen at long-ranges, and the TDWRs should give us more detailed depictions of a hurricane's spiral bands as it approaches the coast.


Figure 2. View of a tornado taken by conventional WSR-88D NEXRAD radar (left) and the higher-resolution TDWR system (right). Using the conventional radar, it is difficult to see the hook-shape of the radar echo, while the TDWR clearly depicts the hook echo, as well as the Rear-Flank Downdraft (RFD) curling into the hook. Image credit: National Weather Service.

No change to time resolution
Like the old NEXRAD data, the new TDWR data will update once every six minutes. The NWS advertises that the TDWR data will be sent out within one minute of when it is measured. The TDWR does scan the atmosphere once per minute at the lowest elevation angle of the radar, but unfortunately, there are no plans to make this rapid scan data available via the free public NOAAPORT feed.

Attenuation problems
The most serious drawback to using the TDWRs is the attenuation of the signal due to heavy precipitation falling near the radar. Since the TDWRs use the shorter 5 cm wavelength, which is closer to the size of a raindrop than the 10 cm wavelength used by the traditional WSR-88Ds, the TDWR beam is more easily absorbed and scattered away by precipitation. This attenuation means that the radar cannot "see" very far through heavy rain. It is often the case that a TDWR will completely miss seeing tornado signatures when there is heavy rain falling between the radar and the tornado. Hail causes even more trouble (Figure 3). Thus, it is best to use the TDWR in conjunction with the traditional WSR-88D radar to insure nothing is missed.


Figure 3. View of a squall line (left) taken using a TDWR (left column) and a WSR-88D system. A set of three images going from top to bottom show the squall line's reflectivity as it approaches the TDWR radar, moves over the TDWR, than moves away. Note that when the heavy rain of the squall line is over the TDWR, it can "see" very little of the squall line. On the right, we can see the effect a strong thunderstorm with hail has on a TDWR. The radar (located in the lower left corner of the image) cannot see much detail directly behind the heavy pink echoes that denote the core of the hail region, creating a "shadow". Image credit: National Weather Service.

Range unfolding and aliasing problems
Another serious drawback to using the TDWRs is the high uncertainty of the returned radar signal reaching the receiver. Since the radar is geared towards examining the weather in high detail at short range, echoes that come back from features that lie at longer ranges suffer from what is called range folding and aliasing. For example, for a thunderstorm lying 48 nm from the radar, the radar won't be able to tell if the thunderstorm is at 48 nm, or some multiple of 48 nm, such as 96 or 192 nm. In regions where the software can't tell the distance, the reflectivity display will have black missing data regions extending radially towards the radar (Figure 4). Missing velocity data will be colored pink and labeled "RF" (Range Folded). In some cases, the range folded velocity data will be in the form of curved arcs that extend radially towards the radar.


Figure 4. Typical errors seen in the velocity data (left) and reflectivity data (right) when range folding and aliasing are occurring. Image credit: National Weather Service.

Ground clutter problems
Since the TDWRs are designed to alert airports of low-level wind shear problems, the radar beam is pointed very close to the ground and is very narrow. The lowest elevation angle for the TDWRs ranges from 0.1° to 0.3°, depending upon how close the radar is to the airport of interest. In contrast, the lowest elevation angle of the WSR-88Ds is 0.5°. As a result, the TDWRs are very prone to ground clutter from buildings, water towers, hills, etc. Many radars have permanent "shadows" extending radially outward due to nearby obstructions. The TDWR software is much more aggressive about removing ground clutter than the WSR-88D software is. This means that real precipitation echoes of interest will sometimes get removed.

For more information
For those of you who are storm buffs that will be regularly using the new TDWR data, I highly recommend that you download the three Terminal Doppler Weather Radar (TDWR) Build 3 Training modules. These three Flash files, totaling about 40 Mb, give one a detailed explanation of how TDWRs work, and their strengths and weaknesses. There is also a full product documentation guide available. I'll be adding the info in this blog entry into the radar help link available on each of our radar pages.

No Atlantic named storm likely this week
The models continue to indicate an extratropical storm that has the potential to evolve into a named subtropical storm will form in the middle Atlantic by Thursday. However, it now appears that there will be too much wind shear for Subtropical Storm Rene to form out of this system.

I'm in San Francisco this week for the annual meeting of the American Geophysical Union, the world's largest climate change conference. I'll be posting daily "post cards" from the conference this week.

Jeff Masters

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72. zoomiami
2:39 AM GMT on December 16, 2008
Sorry to hear that, not fun when family is sick over the holidays.
Member Since: August 13, 2007 Posts: 10 Comments: 4158
71. conchygirl
2:39 AM GMT on December 16, 2008
Quoting zoomiami:
Hi Conchy - how's it going? Almost 80 today - air was back on again. If we only lived a few hours north....
Hey Zoo - us too air came back on - didn't make 80 but still warm and humid. May have to head down your way soon as my Aunt is in the hospital.
Member Since: June 11, 2008 Posts: 24 Comments: 5910
70. zoomiami
2:38 AM GMT on December 16, 2008
Baha - you are only imagining that its going to get slower - its a myth that they use to keep us poor fools working hard.
Member Since: August 13, 2007 Posts: 10 Comments: 4158
69. zoomiami
2:37 AM GMT on December 16, 2008
Hi Conchy - how's it going? Almost 80 today - air was back on again. If we only lived a few hours north....
Member Since: August 13, 2007 Posts: 10 Comments: 4158
68. BahaHurican
2:36 AM GMT on December 16, 2008
Quoting HadesGodWyvern:
as for how many cyclone for the southern hemisphere I seen about 10 for Australia and 10 for Fiji region.. so it might be an active season down south.

There is also a cyclone potential for Australia right now (Western Australia region)
That's pretty high for Oz. They are usually around 6-7 average, I think. Fiji area is usually a bit more active.

Well, at least we are likely to stay occupied during the ATL off-season . . . lol

Once things let up on me at work this week I'll be paying more attention, have time to catch up [and read back].
Member Since: October 25, 2005 Posts: 19 Comments: 22585
67. conchygirl
2:35 AM GMT on December 16, 2008
Quoting sugarsand:
Hey CG!
Cheers!
Hi Sugarsand: Ready for the holidays? Blog pretty quiet but as to be expected this time of the year!

I do see that Pottery is around too!
Member Since: June 11, 2008 Posts: 24 Comments: 5910
66. sugarsand
2:29 AM GMT on December 16, 2008
Hey CG!
Cheers!
Member Since: September 13, 2008 Posts: 9 Comments: 2953
65. conchygirl
2:24 AM GMT on December 16, 2008
Quoting sugarsand:

Ho ho ho Pottery! Had to turn the a/c on tonight. Very humid. Maybe it's the wine:)
me too sugar.....very humid, but agree possibly the wine! LOL
Member Since: June 11, 2008 Posts: 24 Comments: 5910
64. GatorWX
2:16 AM GMT on December 16, 2008
Astro, are you from TX?
Member Since: January 1, 2008 Posts: 0 Comments: 3785
63. GatorWX
2:14 AM GMT on December 16, 2008
I just looked at Wikipedia, but that's been their figure for a couple months, so the people certainly aren't still classified as missing. I imagine many or most of ths listed there as missing were people who relocated or had no communication. Thankyou for the response
Member Since: January 1, 2008 Posts: 0 Comments: 3785
62. zoomiami
2:12 AM GMT on December 16, 2008
First an early ice storm takes out all the electric, and now they have record highs in southern Maine. 57 with snow forecasted for the next few days. The weather is certainly weird.

No wonder the kid has strep.
Member Since: August 13, 2007 Posts: 10 Comments: 4158
61. AstroHurricane001
2:04 AM GMT on December 16, 2008
Quoting all4hurricanes:

Wikipedia says 126 direct, 38 indirect, 202 missing so pretty bad

It's pretty cold where I am in S. Ontario, and windy too. Any water on the ground from today's rain and snow melt has frozen solid.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
60. all4hurricanes
2:02 AM GMT on December 16, 2008
Quoting GatorWX:
Does anyone know what th final death toll from Ike was in the US? I can't find any new information regarding this. Thankyou. PS, it's freaking hot in swFL and muggy too! Looks lik a warm hristmas this year :(

Wikipedia says 126 direct, 38 indirect, 202 missing so pretty bad
Member Since: March 29, 2008 Posts: 0 Comments: 2374
59. GatorWX
2:02 AM GMT on December 16, 2008
Does anyone know the final death toll rom Ike in the US? Can't findany updated info. Thanks
Member Since: January 1, 2008 Posts: 0 Comments: 3785
58. sugarsand
1:55 AM GMT on December 16, 2008
Wine, weather, it's all good.
Member Since: September 13, 2008 Posts: 9 Comments: 2953
57. pottery
1:51 AM GMT on December 16, 2008
Hi there Sugar.
Yep, could be the wine. then again, it could be the weather LOL
Member Since: October 24, 2005 Posts: 0 Comments: 24653
56. sugarsand
1:48 AM GMT on December 16, 2008
Quoting pottery:
Trinidad weather now
time 9:40 pm
temp 75 f
humidity 93%
wind calm

Its going to get a little chilly here around 4:00 am. Forecast is for 71 F.
Mustbe Christmas, or Winter, or something.......

Ho ho ho Pottery! Had to turn the a/c on tonight. Very humid. Maybe it's the wine:)
Member Since: September 13, 2008 Posts: 9 Comments: 2953
55. pottery
1:43 AM GMT on December 16, 2008
Trinidad weather now
time 9:40 pm
temp 75 f
humidity 93%
wind calm

Its going to get a little chilly here around 4:00 am. Forecast is for 71 F.
Mustbe Christmas, or Winter, or something.......
Member Since: October 24, 2005 Posts: 0 Comments: 24653
54. HadesGodWyvern (Mod)
1:38 AM GMT on December 16, 2008
as for how many cyclone for the southern hemisphere I seen about 10 for Australia and 10 for Fiji region.. so it might be an active season down south.

There is also a cyclone potential for Australia right now (Western Australia region)
Member Since: May 24, 2006 Posts: 51 Comments: 46190
53. HadesGodWyvern (Mod)
1:36 AM GMT on December 16, 2008
38. BahaHurican 10:26 PM GMT on December 15, 2008

Hey HGW. Isn't this relatively early for them? I don't remember seeing a notice of a potential storm in SW Indian before January any time recently. Also, any reports on what's expected for the season down south? I'm under some heavy deadlines this week, or I'd pull whatever I find and post it myself.
-----

Baha, no not really the southwest indian ocean cyclone season starts late October (they already had Asma and Bernard this season). It's the Australia and South Pacific cyclone season that starts around December/January.
Member Since: May 24, 2006 Posts: 51 Comments: 46190
52. HadesGodWyvern (Mod)
1:34 AM GMT on December 16, 2008
Mauritius Meteorological Services
Tropical Cyclone Warning Number TWO
PERTURBATION TROPICALE 04-20082009
4:00 AM Reunion December 16 2008
======================================

At 0:00 AM UTC, Tropical Disturbance (1002 hPa) located at 9.4S 68.6E has 10 minute sustained winds of 20 knots with gust of 30 knots. The disturbance is reported as moving west at 4 knots.

Dvorak Intensity: T1.5

Forecast and Intensity
=========================
24 HRS: 09.8S 65.9E - 25 knots (PERTURBATION TROPICALE)
48 HRS: 10.4S 63.3E - 30 knots (DEPRESSION TROPICALE)
72 HRS: 11.2S 60.8E - 25 knots (PERTURBATION TROPICALE)

Additional Information
======================
Convective activity has built close to the center but is fluctuating and remains scattered. The system is barely organized. This system evolves within a neutral environment: Wind shear is weak, upper level divergence is good but weak equatorward, low level inflow is established poleward but not equatorwards. Available NWP models analyze this low and track it west-southwest along the northern periphery of the subtropical high.

AT THIS STAGE, THIS SYSTEM DOES NOT JUSTIFY ISSUANCE OF REGULAR WARNINGS
Member Since: May 24, 2006 Posts: 51 Comments: 46190
51. zoomiami
1:12 AM GMT on December 16, 2008
Hi Pottery - everyone is out shopping or hiding.

I've updated my blog with some santa pics - and some how they all relate to those on the blogs.

Do need help with the first one though - leave a comment about who it best portrays. Would love to have comments and other peoples pics - something fun to do in off season.

Member Since: August 13, 2007 Posts: 10 Comments: 4158
Does anyone know what th final death toll from Ike was in the US? I can't find any new information regarding this. Thankyou. PS, it's freaking hot in swFL and muggy too! Looks lik a warm hristmas this year :(
Member Since: January 1, 2008 Posts: 0 Comments: 3785
Is the new area of convection the low that could have become Rene because if it is then it is looking healty for nothing
Member Since: March 29, 2008 Posts: 0 Comments: 2374
Helloo. No posts for 50 mins on here ??
Well, its still raining where I am.......
Member Since: October 24, 2005 Posts: 0 Comments: 24653
Yup, it's up on the internet from their site, only without dates and times . . .
Member Since: October 25, 2005 Posts: 19 Comments: 22585
Hmmm. . . that map implies NAS radar is reporting again . . .
Member Since: October 25, 2005 Posts: 19 Comments: 22585
Quoting P451:
Speaking of Radar's... interesting image.

US Composite

Snow from California through Texas then arcing towards Ohio.

Lots of cold air in the US so far this fall!

Winter is going to be interesting!


Yep...And Next week it's the east's turn.
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Member Since: Posts: Comments:
Great News about that new radar. Thank to WeatherUnderground to make this posible and thanks for add a station in San Juan PR.

What about posible Rene? The area Seems like it is on his way to make a try! Well lets see whats happened.

Good Evening!
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I just updated my blog and made many maps interactive if anyone would like to review.

TampaSpins Weather Blog Link
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Quoting HadesGodWyvern:
Mauritius Meteorological Services
Tropical Cyclone Warning Number ONE
ZONE PERTURBEE 04-20082009
12:00 PM UTC December 15 2008
======================================

At 12:00 PM UTC, Area of Disturbed Weather (1003 hPa) located at 9.4S 69.8E has 10 minute sustained winds of 20 knots with gust of 30 knots. The disturbance is reported as moving west-southwest at 5 knots.

Dvorak Intensity: T1.5

Forecast and Intensity
=========================
24 HRS: 10.2S 66.1E - 30 knots (DEPRESSION TROPICALE)
48 HRS: 10.7S 63.4E - 30 knots (DEPRESSION TROPICALE)
72 HRS: 11.2S 61.1E - 30 knots (DEPRESSION TROPICALE)

Additional Information
======================
This system evolves within a neutral environment: Windshear has decreased over the area, low inflow is established poleward but not equatorward and mid level lack of humidity.
Available NWP models analyze this low and track it globally westward without deepening it significant at short to medium range.

AT THIS STAGE, THIS SYSTEM DOES NOT JUSTIFY ISSUANCE OF REGULAR WARNINGS.
Hey HGW. Isn't this relatively early for them? I don't remember seeing a notice of a potential storm in SW Indian before January any time recently. Also, any reports on what's expected for the season down south? I'm under some heavy deadlines this week, or I'd pull whatever I find and post it myself.
Member Since: October 25, 2005 Posts: 19 Comments: 22585
Quoting cchsweatherman:
Just stopping by to check up on everyone. Been quite some time since I last visited the blogs. Been having a rough semester that just came to an end last Thursday.

Anyways, yet another well-written and impeccable blog post by Dr. Masters. Will be looking forward to using this new radar technology to track thunderstorms here in South Florida come the spring. Seems like the resolution will be much better and this new radar technology will provide so much more data.

By the way, it seems like all the computer models are onboard with brief subtropical development in the Central Atlantic before wind shear takes control. Will be watching this region throughout the week in case.

If you have been visiting my site within the past month, I apologize for not having updated it for quite some time. Just been really busy with finals and trying to overcome some emotional hurdles that have come over the past couple months. This morning, I did a full update on my site.

Well, thanks for the update Dr. Masters and hope everyone has a great holiday season. I will be stopping in from time to time during the "offseason".
Hey, cchs. Good to see u made it through the term. One good thing about the way school is set up is that it allows u to get through a lot of the hurricane season before things really start to tighten up workload wise. Hope u do ok with ur finals and stuff so u can have a little time in the blog without feeling guilty . . . lol
Member Since: October 25, 2005 Posts: 19 Comments: 22585
Evening, everybody.

Glad to see the info from the new dopplar system coming online. I'm really glad to see that FLL is one of the first sites to be launched.
Member Since: October 25, 2005 Posts: 19 Comments: 22585
Wow, winds here are gusting up to 70 km/h (40 mph), and the temperature dropped 7C in 5 hours (that's 10F). By the way the American Geophysical Union was the organazation that reported the melting of the methane clathrates, I look forward to more information regarding this issue.
Member Since: August 30, 2008 Posts: 8 Comments: 2835
35. Skyepony (Mod)
Excellent blog Dr Masters. I've been playing with these so this blog & links are most appreciated. & the weather toys..ya'll have outdone yourselves. I haven't seen anyone else put these out to the public.


Noticed something...Looks like we have entered La Niña conditions... NINO 3,4 is below -0.5.
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WSR 88 explained..Link
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Thanks for the Update on the Radar. That is good news, that the public is able to access this info. Nice.

Been raining here, on and off, all day. Cool too.81F now. (well its all relative, you know??) Took the opportunity to re-pot some trees, and move things around in prep. for the coming dry season. (will go to the Mystic Masseur in the morning, for healing of burned-out back muscles)

Looks like we will have rains for a couple days....
Member Since: October 24, 2005 Posts: 0 Comments: 24653
Good afternoon all,
just checking in on everybody and hope to get the radar in this area..... Sounds like a new toy to get used too....

Thank You Dr Masters for the update and great info on the new radars.....

Taco :0)
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25. tornadofan 12:17 PM PST on December 15, 2008
Amy - nothing on Amazon. Though if you google "Idiot's guide to fancy new radars?" this blog comes up number 1.



why am I not surprised?

;)
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25. tornadofan 8:17 PM GMT on December 15, 2008
Amy - nothing on Amazon. Though if you google "Idiot's guide to fancy new radars?" this blog comes up number 1.

---
LMAO
Member Since: May 24, 2006 Posts: 51 Comments: 46190
I just learned all about the WSR 88 in college and now your telling me its going to be phased out! WHAT!
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Amy - nothing on Amazon. Though if you google "Idiot's guide to fancy new radars?" this blog comes up number 1.
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Thanks Doc, have a good time in Frisco
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Anyone got an Idiot's guide to fancy new radars?

did you try Amazon.com?

;)
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Bravo Weather Underground your commitment to technology makes your website superior to others! Oh by the way, Dr.Masters thank you for the terrific innovative update.
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.