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Press 'OK' to continue. principles of meteorological doppler radar vcp selection lesson motivation your choice of vcp during an event impacts the radar data you have available supplemental scans use the link to learn more about wsr-88d sites that collect data on supplemental tilts clear air precipitation precipitation often requires a vcp with a more thorough scan than clear skies vcp 12 vcp 34 examples of cone of silence: sampling speed wsr-88d rotation rate impacts data quality: slower rotation: higher data quality high rotation: lower data quality waveforms wsr-88d has two primary waveforms: split cuts – alternating full sweeps of each waveform batch cuts – alternating pulses of cs & cd on one sweep vcp space vcp space is the area (shown in blue) swept out by all the tilts in the volume scan adding tilts to the vcp makes it longer vcp scanning strategy elements vcp space vcp space vcp space vcp space waveforms waveforms waveforms waveforms sampling speed sampling speed sampling speed sampling speed cone of silence cone of silence cone of silence cone of silence clear air/precip clear air/precip clear air/precip clear air/precip supplemental scans supplemental scans supplemental scans supplemental scans pulse length pulse length pulse length pulse length vcp traits: most complete vcp space coverage 1 sails or 4 mrle tilts available sz-2 range unfolding used on split cuts best precip mode vcp data quality mpda available on lowest 1-2 tilts vcp traits: designed for severe convection allows for up to 3 sails or 4 mrle tilts differs from vcp 12 by using sz-2 also allows for mpda on lowest 1 or 2 tilts enabling mpda will lengthen scan times vcp traits: designed for widespread precipitation strength: combination of mpda and sz-2 drawback: prfs uneditable vcp traits: designed for severe convection uses legacy range unfolding faster volume scans w/ more rf areas up to 3 sails or 4 mrle tilts vcp traits: clear air mode uses sz-2 on split cuts uses a short pulse (unlike vcp 34) why long pulse? higher sensitivity lower vmax vcp traits: clear air mode uses sz-2 on split cuts unique feature: long pulse vcp details vcp 34 vcp 34 vcp 34 vcp 34 vcp 35 vcp 35 vcp 35 vcp 35 vcp 12 vcp 12 vcp 12 vcp 12 vcp 112 vcp 112 vcp 112 vcp 112 vcp 212 vcp 212 vcp 212 vcp 212 vcp 215 vcp 215 vcp 215 vcp 215 vcp selection: science fact & fiction in reality, many things may drive vcp selection: vcp system specs? rotate too fast? recent maintenance? what should drive it: the weather! time for a reminder: mode selection function vs. precipitation status mode selection function clear air mode precip mode msf changes between modes precipitation status (and related parameters) determine accumulation these are separate processes! precipitation status large-scale precip options: vcp 112 (general rf mitigation using mpda & sz-2) vcp 212 (tropical cyclone tornado threats) options: vcp 212* or vcp 12* (more on specifics shortly) *be judicious in use of sails/mrle tilts! vcp 215 an option for hail only severe convection options: vcp 34 (light winds & precip), vcp 35 (light precip & strong winds), vcp 215 (everything else) winter precip light precip options: vcp 34 (light winds), vcp 35 (everything else) remember: precipitation can accumulate in clear air mode! clear air default: vcp 35 precip default: vcp 215 common example: change default precip mode to 212 during warm season vcp selection guidance default vcps default vcps default vcps default vcps light precip light precip light precip light precip winter precip winter precip winter precip winter precip severe convection severe convection severe convection severe convection large-scale precip large-scale precip large-scale precip large-scale precip the vcp 12/212 dilemma tradeoff: more scans/dedicated oversight vs. less rf, oversight, & updates vcp 212: longer scan times better reduces rf sails/mrle use makes time difference larger vcp 12: shorter scan times allows for prf sectors optimized data requires more human interaction payne (2024) vcp 12* vcp 212*(fastest) vcp 212*(slowest) standard 4:06 4:25 4:42 sailsx1 4:37 4:56 5:24 sails/mrlex2 ~5:08 ~5:31 ~6:06 sails/mrlex3 ~5:39 ~6:06 ~6:48 mrlex4 5:53 6:20 7:02 *avset not activated for times shown vcp selection summary there are 6 vcps available: 2 clear air, 4 precipitation mode all 6 use different scanning strategy elements weather should be primary reason behind vcp selection when deciding on vcp, remember: vcps 35 and 215 are standard defaults vcp 34 (long pulse) for higher sensitivity in light winds vcps 212 or 12 with severe convection vcp 112 for large scale systems to avoid rf incorrect incorrect. vcp 34 don’t use mrle. continue continue continue continue continue continue incorrect incorrect. short pulses are common among most vcps. continue continue continue continue continue continue incorrect correct! the use of a long pulse allows vcp 34 to have a higher level of sensitivity than all of the other vcps. continue continue continue continue continue continue incorrect incorrect. vcp 34 doesn’t use the mpda range unfolding technique. continue continue continue continue continue continue mpda mpda mpda mpda mpda mpda long pulse long pulse long pulse long pulse long pulse long pulse short pulse short pulse short pulse short pulse short pulse short pulse mrle mrle mrle mrle mrle mrle vcp 34 is different from all the other vcps because of their use of: incorrect incorrect. if multiple cd scans are used with varying prfs, it can help eliminate areas of range folding. however, including of more cd scans doesn’t in and of itself improve data quality. continue continue continue continue continue continue incorrect correct. if the antenna rotates more slowly, more pulses can be included at each range gate. continue continue continue continue continue continue incorrect incorrect. the size of the cone of silence is related to the number of elevation angles, not the overall data quality. continue continue continue continue continue continue incorrect incorrect. the number of elevation angles doesn’t impact the overall quality of the data collected. continue continue continue continue continue continue including fewer elevation angles including fewer elevation angles including fewer elevation angles including fewer elevation angles including fewer elevation angles including fewer elevation angles having a larger cone of silence having a larger cone of silence having a larger cone of silence having a larger cone of silence having a larger cone of silence having a larger cone of silence using a slower antenna rotation using a slower antenna rotation using a slower antenna rotation using a slower antenna rotation using a slower antenna rotation using a slower antenna rotation including more contiguous doppler scans including more contiguous doppler scans including more contiguous doppler scans including more contiguous doppler scans including more contiguous doppler scans including more contiguous doppler scans all other factors being equal, which of the following changes will result in higher radar quality data: incorrect your selections for this question did not accurately describe all of the vcps that use the sz-2 range unfolding algorithm. if you need a refresher, this information is provided on the vcp details slide in the presentation. continue continue continue continue continue continue correct that's right! you selected all of the correct responses for this question. continue continue continue continue continue continue vcp 34 vcp 34 vcp 34 vcp 34 vcp 34 vcp 34 vcp 35 vcp 35 vcp 35 vcp 35 vcp 35 vcp 35 vcp 12 vcp 12 vcp 12 vcp 12 vcp 12 vcp 12 vcp 112 vcp 112 vcp 112 vcp 112 vcp 112 vcp 112 vcp 212 vcp 212 vcp 212 vcp 212 vcp 212 vcp 212 vcp 215 vcp 215 vcp 215 vcp 215 vcp 215 vcp 215 which of the following vcps use the sz-2 range unfolding algorithm in some capacity? incorrect incorrect. while faster antenna rotation may lead to additional “wear and tear”, that shouldn’t be the primary factor in your vcp choice. continue continue continue continue continue continue incorrect incorrect. all vcps operate well within system specifications. continue continue continue continue continue continue incorrect incorrect. while no one wants a hardware failure, that shouldn’t be the primary factor in choosing a vcp. continue continue continue continue continue continue incorrect correct. the weather conditions should drive what vcp you choose. continue continue continue continue continue continue monitoring the weather most effectively monitoring the weather most effectively monitoring the weather most effectively monitoring the weather most effectively monitoring the weather most effectively monitoring the weather most effectively preventing hardware failure preventing hardware failure preventing hardware failure preventing hardware failure preventing hardware failure preventing hardware failure staying within system specifications staying within system specifications staying within system specifications staying within system specifications staying within system specifications staying within system specifications using the slowest antenna rotation needed using the slowest antenna rotation needed using the slowest antenna rotation needed using the slowest antenna rotation needed using the slowest antenna rotation needed using the slowest antenna rotation needed the primary factor that should impact your vcp choice should be: incorrect incorrect. you didn’t select the two correct responses for the default clear air and precipitation mode vcps. if you need a refresher, this information is found on the vcp selection guide slide in the presentation. continue continue continue continue continue continue correct correct! those are the standard default vcps for clear air and precipitation modes. continue continue continue continue continue continue vcp 34 vcp 34 vcp 34 vcp 34 vcp 34 vcp 34 vcp 35 vcp 35 vcp 35 vcp 35 vcp 35 vcp 35 vcp 12 vcp 12 vcp 12 vcp 12 vcp 12 vcp 12 vcp 112 vcp 112 vcp 112 vcp 112 vcp 112 vcp 112 vcp 212 vcp 212 vcp 212 vcp 212 vcp 212 vcp 212 vcp 215 vcp 215 vcp 215 vcp 215 vcp 215 vcp 215 the standard default vcps for clear air and precipitation modes recommended by the roc are (select the two that apply): incorrect incorrect. you didn’t select the best vcp options to use during severe convective weather. if you need a hint, the information is provided on the vcp selection guide slide in the presentation. continue continue continue continue continue continue correct correct! vcps 212 and 12 provide the best scanning strategies for severe weather operations. continue continue continue continue continue continue vcp 34 vcp 34 vcp 34 vcp 34 vcp 34 vcp 34 vcp 35 vcp 35 vcp 35 vcp 35 vcp 35 vcp 35 vcp 12 vcp 12 vcp 12 vcp 12 vcp 12 vcp 12 vcp 112 vcp 112 vcp 112 vcp 112 vcp 112 vcp 112 vcp 212 vcp 212 vcp 212 vcp 212 vcp 212 vcp 212 vcp 215 vcp 215 vcp 215 vcp 215 vcp 215 vcp 215 when severe convective weather is expected, which vcps are best to use in general (i.e., no caveats): incorrect incorrect. vcp 112 would best choice for a widespread, tropical system. continue continue continue continue continue continue incorrect incorrect. vcp 12 would be the best choice for widespread severe convection. continue continue continue continue continue continue correct correct. vcp 215 is the best choice amongst those listed here. continue continue continue continue continue continue incorrect incorrect. vcp 34 would be a good choice if there was light winds and you needed higher sensitivity to detect light precipitation. continue continue continue continue continue continue vcp 34 vcp 34 vcp 34 vcp 34 vcp 34 vcp 34 vcp 215 vcp 215 vcp 215 vcp 215 vcp 215 vcp 215 vcp 12 vcp 12 vcp 12 vcp 12 vcp 12 vcp 12 vcp 212 vcp 212 vcp 212 vcp 212 vcp 212 vcp 212 which vcp is best during a winter weather event with widespread precipitation and strong winds? incorrect incorrect. contiguous surveillance waveforms provide the best possible rmax. continue continue continue continue continue continue correct correct. cd waveforms provide the best possible maximum unambiguous velocity. continue continue continue continue continue continue true true true true true true false false false false false false true or false: contiguous doppler waveforms provide the best possible rmax (maximum unambiguous range). andrew.c.wood@noaa.gov <Document xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Content> <Block> <Style LeadingMargin="0" FirstLineMargin="0" Justification="Left" ListLevel="1" LineSpacingRule="Multiple" LineSpacing="20" SpacingBefore="4.32" SpacingAfter="0"> <ListStyle ListType="None" ListTypeFormat="Plain" Start="0" Color="#000000,00" BulletChar="•" BulletFont="Arial"> <BulletPicture Size="0x0" /> </ListStyle> </Style> <Span Text="Welcome to this lesson on VCP Selection. This lesson is part of the Principles of Meteorological Doppler Radar topic in the Radar & Applications Course. Let’s get started."> <Style FontFamily="+minor" FontSize="11" FontIsBold="False" FontIsItalic="False" FontIsUnderline="False" FontIsStrikeout="False" ForegroundColor="dk1,00" Elevation="Normal" DisplayCase="AsIs" LinkColor="dk1,00" /> </Span> </Block> </Content> </Document> <Document xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Content> <Block> <Style /> <Span Text=" So, why do we have a lesson on Volume Coverage Pattern (or VCP) Selection in RAC? Well, your choice of VCP during an event can have significant positive or negative consequences on the radar data you have available to interrogate the atmosphere. Your office will have default VCPs set up for your office’s dedicated Radar Product Generator. Those options will be chosen automatically for you when specific precipitation-based criteria are or are not met. However, there are several situations where you will likely want to either choose one of the non-default VCPs or switch back to a default VCP from a non-default option based on the weather in your area. This lesson will discuss your options, what makes them unique from each other, and when you will want to choose them."> <Style FontSize="11" /> </Span> </Block> </Content> </Document> <Document xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Content> <Block> <Style /> <Span Text="Main Slide: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="With the release of RDA/RPG Build 24, six different VCPs are available to use at each WSR-88D. Some of the elements that make one VCP different from another include: the VCP space, the waveforms used to sample the atmosphere, the length of the radar pulse transmission, the sampling speed, the cone of silence, whether the VCP was designed for clear air or precipitation, and whether supplemental scans are available for a particular radar site (Boettcher et al., 2022). Use the buttons on the left to learn more about these topics.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="VCP Space: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="Each VCP uses a variety of elevation angles to sample a “VCP space” in the atmosphere (Heinselman and Torres, 2011). These regions, which are highlighted in blue in the example shown, show what the radar beam can observe with a particular VCP. Increasing your VCP space by adding more tilts will increase the length of time it takes to complete the volume scan.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="Waveforms: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="The WSR-88D uses two primary waveforms to measure meteorological echoes: Contiguous Surveillance (CS) and Contiguous Doppler (CD). CS scans use a low PRF to provide the best maximum unambiguous range, while CD scans use a high PRF to provide the best maximum unambiguous velocity. Combinations of both CS and CD scans on a single tilt can provide both benefits. Split cuts alternate separate, full sweeps of CS and CD pulses, while batch cuts alternate between CS and CD pulses while completing a single sweep.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="Pulse Length: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="The standard pulse length for most WSR-88D VCPs is referred to as short pulse. One VCP uses a longer duration pulse that increases the sensitivity of the returned power. The downside to use the longer pulse is a lower maximum unambiguous velocity compared to similar VCPs that use the shorter pulse.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="Sampling Speed: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="Different scanning strategies often require the antenna to sample the atmosphere at different rates. As a result, the radar antenna will rotate at different speeds to meet those needs. The faster that the radar rotates, the fewer independent samples the radar can acquire to build the various radar products. So, all other scanning strategy elements being equal, the faster the rotation rate, the lower the data quality (Smith, 1995).
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="Cone of Silence: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="The “cone of silence” is the conical region located above the RDA that cannot be sampled by that radar (Leone et al., 1989). The size of the cone of silence is directly related to the highest elevation tilt included in the volume scan. If precipitation echoes occur in a radar’s cone of silence, you will need to switch to a different, nearby radar to observe those meteorological targets.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="Clear Air/Precip: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="VCPs generally fall into two categories: Clear air and precip modes. Precipitation events often require a VCP with a more thorough scan of the atmosphere. The clear air mode VCPs use scanning strategies to maximize data quality when there is little to no meteorological returns visible to the radar. So, the antenna tends to rotate slower and sample fewer elevations angles in clear air mode.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="Supplemental Scans: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="A handful of WSR-88D sites have an additional, supplemental scan available below 0.5 degrees. The exact elevation angle varies from site to site, but the scan is somewhere between -0.2 to 0.4 degrees elevation. A list of the sites with a supplemental scan, and the specific elevation angle of that scan, can be found using the link at the bottom of the slide or by clicking on the resources tab. "> <Style FontSize="11" /> </Span> </Block> </Content> </Document> <Document xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Content> <Block> <Style /> <Span Text="Main Slide: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="So, now that you know the basic concepts that go into a volume coverage pattern, let’s look at each available VCP in more detail. Use the buttons on the slide to toggle between all six of the VCPs.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="VCP 34: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="VCP 34 is a clear air VCP that uses 7 tilts and can include one SAILS tilt. You can see the scanning strategy for each tilt in the graphic. VCP 34 uses the SZ-2 unfolding algorithm on split cut tilts (which reduces range folded data) and is unique from other VCPs in that it uses a long pulse. Why use a long pulse? The longer pulse offers higher sensitivity, but a lower maximum unambiguous velocity. VCP 34 volume scans take approximately 10 minutes to complete.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="VCP 35: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="VCP 35 is a clear air VCP with 9 tilts and can include one SAILS tilt. You can see the scanning strategy for each tilt in the graphic provided. VCP 35 uses the SZ-2 range unfolding technique on split cut tilts and (unlike VCP 34) uses a shorter pulse like precipitation mode VCPs. VCP 35 volume scans take approximately 7 minutes to complete.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="VCP 12: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="VCP 12 is a precipitation mode VCP designed for convective weather situations (Brown et al., 2005). It uses 14 tilts with the scanning strategies by tilt shown in the graphic. VCP 12 is unique in that it is the only VCP that does not incorporate the SZ-2 range unfolding algorithm. This provides users faster volume scan times but at the trade off of the most areas of range folded data. Up to 3 SAILS or 4 MRLE tilts can be included in a single volume scan. A complete VCP 12 scan without SAILS or MRLE tilts takes just over 4 minutes.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="VCP 112: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="VCP 112 is a precipitation mode VCP designed for large-scale (or widespread) precipitation situations where minimizing range folding is important. It has 14 tilts and one SAILS tilt can be implemented. The strength of this VCP is in the combination of the MPDA and SZ-2 algorithms at lower levels virtually eliminates range folded data there. However, the trade off is that the Doppler pulse PRFs aren’t editable for the split cuts where those techniques are used. A complete VCP 112 volume scan without SAILS takes approximately 5.5 minutes to complete.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="VCP 212: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="VCP 212 is a precipitation mode VCP designed for convective weather situations. This scanning strategy has 14 tilts in a full volume scan and up to 3 SAILS tilts or 4 MRLE tilts can be included. VCP 212 differs from VCP 12 by the techniques used to mitigate range folding. VCP 212 uses the SZ-2 range unfolding technique on the three lowest tilts. Forecasters can also enable the MPDA range unfolding technique on the lowest 1-2 tilts to further eliminate range folded data. However, enabling MPDA will add additional time to the volume scan. A complete VCP 212 scan without SAILS, MRLE or MPDA tilts takes between 4.5 and 5 minutes to complete.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="VCP 215: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="VCP 215 is a precipitation mode VCP designed for general surveillance. VCP 215 provides the most complete VCP space coverage with 15 different elevation angles, and can include 1 SAILS or up to 4 MRLE tilts. The SZ-2 range unfolding algorithm is used on the lowest three tilts. The radar antenna rotates more slowly in VCP 215 than other precipitation mode VCPs which provides the best data quality. Forecasters can enable the MPDA range unfolding technique on the lowest 1-2 tilts to further eliminate range folded data. However, enabling this feature lengthens the volume scan time. A full VCP 215 volume scan takes approximately 6 minutes to complete.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text=""> <Style FontSize="11" /> </Span> </Block> </Content> </Document> <Document xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Content> <Block> <Style /> <Span Text=" Many factors may go through your mind as you are deciding which VCP to use: How does a particular VCP operate with respect to system specifications, does a particular VCP make the antenna rotate too fast?, has our local staff been talking about hardware failures lately, or even radar maintenance issues. While all of these topics may enter your head, the one factor that should drive your VCP selection decision-making is one that I didn’t mention in that list: the weather."> <Style FontSize="11" /> </Span> </Block> </Content> </Document> <Document xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Content> <Block> <Style /> <Span Text=" Before we discuss which VCPs to use in what circumstances, it’s time for a quick reminder. The Mode Selection Function is the application that monitors echo coverage and automatically switches between clear air and precipitation modes. There’s also precipitation status and the various related parameters that the RPG uses to determine if precipitation accumulation should begin, continue, or stop. These are separate processes. It’s important that forecasters realize that the radar can be in a clear air VCP and still accumulate precipitation. Likewise, a radar can be in a precipitation mode VCP and not accumulate precipitation. "> <Style FontSize="11" /> </Span> </Block> </Content> </Document> <Document xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Content> <Block> <Style /> <Span Text="Main Slide: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="We have created this flowchart to help with the VCP selection process. Choose from the buttons on the left to learn more about VCP selection involving specific weather conditions. 
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="Default VCPs: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="The system default volume coverage patterns for the WSR-88D are VCP 35 for clear air mode and VCP 215 for precipitation. Offices still have the ability to configure the default VCPs locally, but these defaults are recommended by both the ROC and WDTD. A common example of how an office my alter the default VCPs is to change the precipitation mode default to VCP 212 during the warm season due to more frequent convective events occurring then.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="Light Precip: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="Drizzle and other light radar return situations can be tricky when choosing your VCP. VCP 34 offers the best opportunity to detect any echoes that are present due to its use of a long pulse. However, VCP 34 only helps when winds are relatively light because of its lower maximum unambiguous velocity. When winds are stronger, VCP 35 will be the better choice. Either way, remember that precipitation can accumulate in the RPG algorithms even when using a clear-air mode VCP. "> <Style FontSize="11" FontIsBold="False" /> </Span> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="Winter Precip: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="Winter precipitation events can also be tricky. For winter events with light precipitation, some offices prefer to stay in clear air mode. If that describes your office, then use VCP 34 for light winds and VCP 35 for strong winds. For any winter events with significant snow or sleet accumulations, VCP 215 will likely be your best option.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="Severe Convection: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="Anytime your local radar is in precipitation mode and severe convection is expected, VCPs 12 and 212 are recommended options. We will discuss specifics of VCP 12 and 212 in more detail later. Some forecasters may choose to use VCP 215 for severe convection when the ONLY threat is hail because the VCP space aloft can be a little better, but VCPs 12 and 212 will generally be preferable even in that situation.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text="Large-Scale Precip: "> <Style FontSize="11" FontIsBold="True" /> </Span> <Span Text="When a large-scale precipitation system (such as a tropical cyclone) impacts your local area, the best VCP option will be VCP 112. This VCP performs best at mitigating range folding when radar returns cover the area surrounding the radar out to 200 km or more. If a significant tornado threat exists with one of these systems, consider using VCP 212 instead."> <Style FontSize="11" /> </Span> </Block> </Content> </Document> <Document xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Content> <Block> <Style /> <Span Text=" When choosing between VCPs 12 or 212, you decide between speed and convenience. VCP 212 reduces range folded data on the velocity products, but it comes at a cost of slightly slower scans. When you add SAILS and MRLE tilts, those slower scan times can add up to an additional minute or so per volume scan depending on which PRF VCP 212 uses. The higher the PRF, the slower the radar scans. I should also note the times shown in the table are for a complete volume scan, so using AVSET would likely decrease all of the volume scan times.
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text=" While VCP 12 does not have this limitation, you do run into a different problem. Your storm of interest may have range folded velocity data at a critical time due to its range from the radar and PRF. As a result, we recommend routine RPG HCI monitoring when using VCP 12 and adjusting the PRF as needed to prevent this issue from impacting warning operations."> <Style FontSize="11" /> </Span> </Block> </Content> </Document> <Document xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Content> <Block> <Style /> <Span Text=" In summary, you have 6 different volume coverage patterns to choose from on the WSR-88D: 2 in clear air mode and 4 in precipitation mode. Each VCP uses slightly different scanning strategy elements to set it apart from the others. When choosing which of the 6 to use, the current or expected weather conditions should drive your decision. While choosing the best VCP for a particular situation can be tricky, keep these ideas in mind. VCPs 35 and 215 were designed to be default VCPs for clear air and precip modes, respectively. They work for a lot of situations. If you need higher sensitivity to detect light returns (and the winds aren’t too strong), try VCP 34. During severe convection VCPs 212 or 12 are best. Lastly, VCP 112 can be beneficial when trying to avoid range folded returns during large scale precipitation systems (like tropical cyclones).
"> <Style FontSize="11" /> </Span> </Block> <Block> <Style /> <Span Text=" Now you are ready to take the quiz. Advance to the next slide to proceed."> <Style FontSize="11" /> </Span> </Block> </Content> </Document> <Document xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Content> <Block> <Style /> <Span Text=" If you have passed the quiz, then you have successfully completed this lesson. You are now ready to move onto the next lesson. If you have any questions, please contact us using the e-mail addresses listed on the slide."> <Style FontSize="11" /> </Span> </Block> </Content> </Document>