Dual Polarization Radar - Coming Soon!

[toastido]

Not sure how many of you know this, but the NWS will be rolling out the new Dual-Polarization radars for ALL sites between now and 2012.  Here is an excerpt:

Between now and the end of 2012, the entire fleet of WSR-88Ds (Weather Surveillance Radar -1998 Doppler) is scheduled for a major software and hardware upgrade. This upgrade, known as dual-polarization technology, will greatly enhance these radars by providing the ability to collect data on the horizontal and vertical properties of weather (e.g., rain, hail) and non-weather (e.g., insect, ground clutter) targets.

There is on-line training available for the new radars, and I highly recommend taking these on-line courses.  They recommend taking it no more than 3 months prior to the installation at the existing 88D site you normally use, but I would say take it now, get familiarized with it, and then take it again as a refresher when they do the radar upgrade for your site.

Anyway, enough with that, here's the link to the NWS training page for the Dual-Pol:
http://www.wdtb.noaa.gov/courses/dualpol/Outreach/index.html

There does not appar to be an official upgrade schedule.  I assume they will be doing this when there is a forecasted period of 2+ weeks of benign weather for a particular WFO, but can't be certain. 

Anyway, enjoy!

[Kevin]

This is running WAY behind schedule...but we do have a better idea of the timeline now that *may* see this rolled out across the country...so I wanted to provide an update. The first beta sites will be upgraded in the next two months. Vance, OK and Phoenix, AZ have come online in just the last few weeks.

A very preliminary schedule is out...but if you view this page...note its very possible if not likely the dates mentioned will be pushed back as we get closer. Delays have been continuous since this began. In 2008-2009...the target was to have dual-pol up everywhere by 2010-2011. Clearly...didn't happen.

http://www.roc.noaa.gov/wsr88d/PublicDocs/DualPol/DeploymentSchedule.pdf

Note that most sites in this region are not scheduled to be upgraded until Late 2012 or 2013...so there's no rush to get prepared for getting and interpreting this data. The one exception...again if this schedule holds...which it very well may not...is KNQA (Memphis)...which is expected to be upgraded between December 2011 and January 2012...a much shorter window. I'm not holding my breath...but we'll see what happens.

In the meantime...still feel free to check out WDTB's training area that Toastido posted above...it has a lot of great information. There will be many new terms you'll be hearing about once this finally starts becoming reality...such as the TDS (Tornadic Debris Signature...which will be much better /though not always/ detected with Dual-Pol data).

[Bigm33]

Strange, I thought most radar sites had already been updated in the last few years. I only started hearing of radar-detected "debris balls" last year with the Yazoo City tornado.

[Kevin]

Strange, I thought most radar sites had already been updated in the last few years. I only started hearing of radar-detected "debris balls" last year with the Yazoo City tornado.

A "debris ball" is a signature seen on basic radar reflectivity...which we've been seeing and have known about for years. Granted...after the "super-res" update a few years ago they have been better visible because of the increased data resolution...plus they're mentioned all the time on media and forums such as this one now...even though they are not a newly discovered phenomena.

The "TDS" that dual-pol radars will see will just be a better signature and especially confirmation of such...and will probably be noted on the less-than-obvious cases (not much familiarity with that this year...unfortunately)...because of the new products and technology dual-pol will provide. Dual-pol will also vastly better detect various precipitation types (including hail)...and personally one of its biggest advantages to me will be much much better precipitation rates/totals...far and away better and more accurate than what we see Today.

More info on dual-polarimetric radar can be found here...
http://www.nssl.noaa.gov/research/radar/dualpol.php

[Bigm33]

Wow had no clue  ...thought that was something new they had just discovered recently lol. Will this new radar be GR3 compatible (since i'm considering downloading it here soon) or will they release a new PC program to go with the new radar?

[Kevin]

Wow had no clue  ...thought that was something new they had just discovered recently lol. Will this new radar be GR3 compatible (since i'm considering downloading it here soon) or will they release a new PC program to go with the new radar?

GR2Analyst already is compatible with many of the dual-pol products (has been for a couple of years...mainly for a few private/commercial dual-pol radars that are out there)...but I wouldn't be surprised to see it eventually added to GR3 as the data becomes more widely available on the NWS network.

One other thing to keep note of...these are not new "radars" going up...they are just upgrading the existing ones with the new hardware. Each radar will be down a period of a couple weeks when the upgrades are made...which is another factor that can result in delays depending on weather conditions and forecasts...

[Kevin]

Good News!

The upgrade schedule through the end of 2011 is now final and official...and KNQA still made the list! The window for upgrade will be between December 5 and 18. Atlanta (KFFC) will also be upgraded in this time frame.

There still may be delays that come up during the process...so I still won't be surprised if this slips into January 2012. But unless there's a major problem that develops somewhere...it shouldn't be later than that.

Everybody else...its still looking late 2012 or later though this part of the schedule is not finalized.

[toastido]

Good News!

The upgrade schedule through the end of 2011 is now final and official...and KNQA still made the list! The window for upgrade will be between December 5 and 18. Atlanta (KFFC) will also be upgraded in this time frame.

There still may be delays that come up during the process...so I still won't be surprised if this slips into January 2012. But unless there's a major problem that develops somewhere...it shouldn't be later than that.

Everybody else...its still looking late 2012 or later though this part of the schedule is not finalized.

KHTX and KGWX need it... badly.  These two sites are up and down quite frequently due to issues... might as well go ahead and upgrade them.  Any idea of the schedule for those two sites?  Did they make the 2011 cut ? 

[Kevin]

If you have GR2Analyst with the Dual-Pol Add On...you can already view Live Level II Data from the Beta sites already upgraded...here's a look at KMHX (Moorehead City, NC)...Not much to make out of these images as there's not much going on right now over there...

Differential Reflectivity (ZDR)...


Correlation Coefficient (RHO/CC)...


Differential Phase (PHI)...


Two of the products...Specific Differential Phase (KDP) and Hydrometeor Classification (HCA) are not being produced by the NWS for Level II Data. Gibson Ridge will have to implement customized versions of these through his own algorithms. HCA will probably be most beneficial to the average person...that will be the one that will classify reflectivity areas as rain...big drops...snow...ice...hail...clutter...etc...through analysis of the base products above. There will still be limitations to using HCA...in other words seeing hail on a storm 10kft high still doesn't necessarily mean hail is occurring at the surface...the same limitations to beam width/height with the curvature of the earth will still be present. But...getting much better evidence that it is indeed hail...and not just heavy rainfall...will greatly help determining if a warning is needed and perhaps...hopefully cut back on more unnecessary ones.

Level III data will generate HCA...the Precipitation Products...as well as the Base and some other Derived Data...but at this time GRLevel3 nor any radar program out there support dual-pol in that format...so we'll have to wait for somebody to develop and release it.

[Kevin]

KHTX and KGWX need it... badly.  These two sites are up and down quite frequently due to issues... might as well go ahead and upgrade them.  Any idea of the schedule for those two sites?  Did they make the 2011 cut ? 

Unfortunately...its going to be a while. HTX...GWX...BMX...and OHX are all not scheduled until Dec 2012 - Feb 2013. MRX is not scheduled until Apr 2013 - Aug 2013.

[Kevin]

Here's a quick...basic... real-world application of ZDR from the Moorehead City Radar...



Note the two circles at the top...the ZDR values are somewhat high (2-4). That means returns are horizontally oriented. When these returns are legitimate (not clutter or biological returns)...this usually means rainfall with bigger rain drops. These type of values may also be associated with wet snow...or even melting/water-coated hail. You have to correlate this image with the other DP products (which is what the HCA algorithm tries to do for you) to make a full determination if those are possibilities.

In the larger circle just below...the ZDR values are very small to near zero. This means returns are vertically oriented. When associated with small reflectivity values...this is a signal for light rain or drizzle with small drops. However...if you get low to zero...or negative ZDR in an area co-located with high reflectivity values (greater than 60dbZ)...that is very likely hail. Just like with the first example...there are several other factors/complications/limitations that can change this result...which again calls for correlation with other products being necessary. But again...a basic example here and one we're fairly sure of just with a cursory look of ZDR & BR and knowledge of the environment.

[Kevin]

Minutes later...here's a real-time (likely) hail example from MHX...


Note...Reflectivity values over 60dbZ associated with ZDR values from zero to -1.5. That's a strongly spherical to even vertically oriented return among high reflecitivty...thus we are likely looking at hail. NOTE...this return at 23kft...so there's no certaintity given the altitude and range from the RDA that the hail will even reach the surface.

Alright...I'm done boring you folks. I do find this exciting...I'm hoping the applications dual-pol promises will deliver in the end...

[Eric]

Minutes later...here's a real-time (likely) hail example from MHX...


Note...Reflectivity values over 60dbZ associated with ZDR values from zero to -1.5. That's a strongly spherical to even vertically oriented return among high reflecitivty...thus we are likely looking at hail. NOTE...this return at 23kft...so there's no certaintity given the altitude and range from the RDA that the hail will even reach the surface.

Alright...I'm done boring you folks. I do find this exciting...I'm hoping the applications dual-pol promises will deliver in the end...

So, if I'm understanding correctly, the lower the ZDR values, the greater chance there is for hail?

[Kevin]

So, if I'm understanding correctly, the lower the ZDR values, the greater chance there is for hail?

Possibly

A ZDR near zero indicates a spherical shape to the return. That could be hail...but it also may be small rain drops which get more spherical as they decrease in size (see first example). A negative ZDR means a vertically-oriented return. That also could mean larger hail (at the altitude of concern). Looking for high coincident values of Base Reflectivity will help differentiate these situations. In the example I outlined...with 60dbZ reflectivity values and zero to negative ZDR...it is very likely hail...but that is at 23kft.

But...near zero or negative ZDR could also mean graupel...dry snow...or certain biological scatters. Environment and distribution/movement of echoes will be needed there. The other DP products also again can help in the differentiations. ZDR is just one aspect of dual-pol. Conversely...higher ZDR doesn't mean hail is not in the return...but it is more likely to be mixed with rain drops or perhaps the hail stones are water coated and/or melting. Most cases like this will be small hail...however...not severe-limit (especially when dealing with melting).

Just like Doppler in general...there are drawbacks and limitations that are present. It won't be a perfect process and instantly reduce all False Alarms.

[Kevin]

I've been doing some of the NWS Training on Dual-Pol this week...and I have to say I'm really excited about the potential for identifying the TDS (Tornadic Debris Signatures). Its going to be even more promising than I initially thought. Still not going to show up for every tornado...but there are a lot of documented cases of the TDS...even in EF0 and EF1 tornadoes when there is little to no reflectivity signature of debris being present. The NWS is saying its so promising...that TORs may be able to be verified just by an accurate detection...because when seen it is 100% confirmable that a tornado is in progress...and at the least it will greatly help surveying because it will be picking up on weaker tornadoes. Its still going to be a close range situation to the RDA...but weak tornadoes have been detected with a TDS as far out as 40nm and strong tornadoes 60nm...which is going to cover a lot of ground at each radar site.

Its not going to improve the lead time obviously...the tornado has to be there before the TDS shows up...but again getting confirmation without a report or maybe even a later survey is going to be enormously beneficial. In the "debris balls" we've become used to on reflectivity...its more of a "duh" situation at that point with spotters already reporting the tornado...and just tells us we may have a big deal at that moment...and that will still be important. Nevertheless...we will probably be seeing TORs in the future with a "radar confirmed" basis being possible...rather than just "radar indicated". Exciting stuff that I hope will translate nationwide as dual-pol is deployed.