- 1. Dual-Pol is an additional tool, but doesNOT replace the
other tools in radartoolbox!
2. Dual-Pol will help with the following: Identifying areas of
uniform precip Detecting the presence of hail Locating very large
hail Distinguishing met/non-met targets QPE/locating areas of
heaviest rain rate Detecting tornadic debris Snow vs rain analysis
Updraft location 3. Dual-Pol will not help with the following:
Identifying mesocyclones Determining specific hail size Forecasting
tornadoes Mitigating any of the current radar range effects Making
you more charming, witty, handsome (orbeautiful). However, dropping
Greek letters like phi and rho, or termslike ZDR columns may make
you appear more nerdy atyour next party! Fausetts puns 4. Like
forecasting, in general, radar analysis requires integration of
all, pertinent data.Analyst Environment Dual-Pol SatelliteAction
ProductsLightning ExistingGroundRadar Truth Products 5. Always
start with Z, V, (or SRM) Z limits what is possible: < 40 dBZ:
not hail; > 65 dBZ: mostly hail < 25 dBZ: mainly light rain
(could be heavy snow - winter) > 25 dBZ: probably not
biological, smoke, chaff (crosssection/All Tilts) can verify loops
show evolution SRM/V shows organizational structure/storm forcing:
Convergence/divergence Rotation/shear (MESO/TVS/ETVS) V values near
0 probably indicate clutter/AP (crosssection/All Tilts can verify
6. Next, Correlation Coefficient (CC) Rho in GR2 and research
papers Gives uniformity information High values (0.98-1.00)
indicate uniform particles (i.e all smaller rain drops, drizzle,
smaller snow flakes; infrequently, small graupel/small dry hail)
Medium values (0.92-0.98) indicate mixed types/sizes (small
hail/rain/snow/graupel) Low values (1.00 usually indicate weak,
unreliable data 7. Three Body Scatter Spike in CC:CC TBSS
verydistinctive.Lowest CCvalues severalbins downradial - WHY?Note:
GR2enhancementcurve stopsat 0.75 so a CCCC Zhole shows up 8. CC
uses: Meteorological vs. non-meteorological Large hail (very low CC
- TBSS) Irregularly shaped hydrometeors Tornadic debris (diagnostic
only) Melting layer Rain vs. snow 9. CC limitations: Noisy and/or
values > 1 (pink) with low SNR NBF:Not TBSS signature Extends
completely down-radial Beam broadening: makes CC less definitive at
long ranges 10. Then: Differential Reflectivity (ZDR) Gives
circularity (eccentricity) information Low positive values (0 - 1)
indicate round targets (Zv=Zh) small droplets, dry hail (tumbles),
dry snow (non-aggregated) Medium values (1 2.5) indicate
increasingly flattened targets moderate sized drops, water coated
hail, wet snow or biological High Values (> 2.5) very flattened
targets large rain drops (possibly with small ice cores),
biological Significant negative values (< -0.5) either
vertically oriented targets (i.e mainly ice needles) or possibly
large hail, due to Mie scattering/re-polarization) effects 11.
USEFUL APPROXIMATION:For ZDR 2.0 dB (in rainsituations):Major axis
diameter (mm) 0.9 (ZDR) 12. ZDR uses: Hail detection Updraft (ZDR
Column) ZDR > 1 dBZ above 0oC level x-section/FSI very useful in
identifying Tornadic debris identification low ZDR due to random
orientation Melting layer increased ZDR Rain/snow transition area
Frozen precipitation types 13. ZDR columns - shows liquid above 0oC
Found along updraft flanks in sheared environments Coincides with
updraft in weak Sheared environments Usually NOT seen when cloud
base is above 0oC Can be used to track developing updrafts,
anticipate storm splitting and estimate updraft strength Use
all-tilts or ZDR X-section along with CC to confirm 14. ZDR
limitations: Large target bias (ZDR less w hail present) Particle
density - (ZDRice < ZDRH20) Mie scattering (may switch signs)
Low signal to noise ratio (SNR) ZDR less reliablewhen CC < 0.9
15. Finally: Specific Differential Phase (KdP) Gives Liquid Water
Content information,KdP = f(dropsize,dropnumber) Higher values =
higher rain rates Only higher ZDR values contribute Therefore,
insensitive to most hail Not displayed on AWIPS when CC < 0.90.
Note: the integrated version, Phi, is available on GR2 atCC <
0.90 16. KdP uses: Heavy rain (only) High values on AWIPS High rate
of change on GR2 Heavy rain mixed with hail The more hail (i.e.
less rain), the lower KdP Cold vs. warm rain processes Warm rain
processes (lower ZDR higher KdP) Cold rain processes (higher ZDR
lower KdP) For KDP 2, rainrate KDP * 1.4 17. KdP limitations: Not
computed in bins with CC< 0.90 (black holes inthe data),
However, GR2 displays all data Noisy/black in low SNR Affected by
NBF No data in the areas where CC has down-radial anomalies 18.
Lgt/Mod R Heavy Rain Big Drops Hail / (mixed w R)Graupel Dry Snow
Wet SnowIce Crystals 19. Not hail Fairly uniform type Can include
large drops Not heavy RLgt/Mod R Heavy Rain Big Drops Hail / (mixed
w R)Graupel Dry Snow Wet SnowIce Crystals 20. Lgt/Mod R Heavy Rain
Big Drops Hail / (mixed w R)Graupel Dry Snow Wet SnowIce Crystals
21. Hail presentCan be quitenon-uniformCan includelarge
dropsDepending on% of R, couldbe anythingLgt/Mod R Heavy Rain Big
Drops Hail / (mixed w R)Graupel Dry Snow Wet SnowIce Crystals 22.
Lgt/Mod R Heavy Rain Big Drops Hail / (mixed w R)Graupel Dry Snow
Wet SnowIce Crystals 23. Not hail Probably not pure R, dry S
Implies possible flattening (i.e. water Not rainLgt/Mod R Heavy
Rain Big Drops Hail / (mixed w R)Graupel Dry Snow Wet SnowIce
Crystals 24. Lgt/Mod R Heavy Rain Big Drops Hail / (mixed w
R)Graupel Dry Snow Wet SnowIce Crystals 25. Not hailSomewhat
uniformto uniformDepends on watercoating not largedropsDepends on
watercoating not R+Lgt/Mod R Heavy Rain Big Drops Hail / (mixed w
R)Graupel Dry Snow Wet SnowIce Crystals 26. Lgt/Mod R Heavy Rain
Big Drops Hail / (mixed w R)Graupel Dry Snow Wet SnowIce Crystals
27. Not hailSomewhat uniformto uniformModerate to
largeraindropsRain rates low tovery lowLgt/Mod R Heavy Rain Big
Drops Hail / (mixed w R)Graupel Dry Snow Wet SnowIce Crystals 28.
Lgt/Mod R Heavy Rain Big Drops Hail / (mixed w R)Graupel Dry Snow
Wet SnowIce Crystals 29. Not hail, heavy rain, but too high for IC
Uniform type Fairly circular, not large drops Very low LWCLgt/Mod R
Heavy Rain Big Drops Hail / (mixed w R)Graupel Dry Snow Wet SnowIce
Crystals 30. Lgt/Mod R Heavy Rain Big Drops Hail / (mixed w
R)Graupel Dry Snow Wet SnowIce Crystals 31. Could contain R or
A.Too high for S, R-Fairly uniform touniform. Not much AMay contain
largeraindropsMay include R+Lgt/Mod R Heavy Rain Big Drops Hail /
(mixed w R)Graupel Dry Snow Wet SnowIce Crystals 32. Lgt/Mod R
Heavy Rain Big Drops Hail / (mixed w R)Graupel Dry Snow Wet SnowIce
Crystals 33. Trick question:We saw this earlier.Didnt want to betoo
predictable!Lgt/Mod R Heavy Rain Big Drops Hail / (mixed w
R)Graupel Dry Snow Wet SnowIce Crystals 34. HydroClassification
Algorithm Product: Use as a safety net Can have significant errors
- GIGO Range folding Weak signal Only indicates type at radar level
Only highest rated type assigned even if valueis 0.001 higher than
any other Weightings derived at Norman, OK Not available currently
on GR2 35. NOT BlowingDustIncludes rain w.significant hail 36.
Precipitation Products:Depending on Z, ZDRand KDP any one ofthree
different Z-RRelationships may beused.Legacy precip
productscontinue in DP 37. DHRDPANO BIASOHPDSPSTPDP - Legacy 38.
Precipitation Products uses: Should give better rain estimates in
mixed rain/hailsituations Non-met scatters dont contaminate
Non-melted hail/snow dont contaminate Melting hail/wet snow
contaminate less User selectable precip (DUA) allows
accumulationdown to 15 minute increments 39. Precipitation Products
limitations: Z-R used depends on HCA output No bias applied (still
have legacy products) Z-R for frozen hydrometeors determined
fromcentral OK data Below beam effects still apply 40.
Hi-resolution Models useful for: Anticipating potential storm
structures Refining location/timing (IF occurrence) Steering
Assessing intensity through proxy parameters 41. Poor Mans Severe
Storm Ensemble Fcst(PMSSEF): Run around midday for period 16Z-12Z
42. SPC RAP analysis two versions on EPZ home page Rollover
Lightscribe 43. Convective Analogs:SPC MARSSt Louis U - CIPS 44.
SPC SREF:Ensembles, likeanalogs, help todefine the rangeof possible
eventsand give usefulinformation onthe time andspatial limits
ofimpact weather. 45. JAAWIN point severe ensembles (see me to
request): 46. WDSS-II Radar Storm Cells: 47. Google Traffic:Useful
for seeingwhere weather isimpacting trafficon I-10/25 and U.S.70
between LasCruces and Organ.Road speeds can bea clue to heavy
rainor hail. 48. Mine Info kml: Contains:Twitter searchWebcamsLinks
to scanner feedsLinks to DoT sites 49. Check frequently for MCDs
will usually precede watchissuances For strong veering (backing)
shear profiles bias boxes tothe right (left) respectively For
strong straight shear profiles widen the boxdownstream to allow for
storm splitting For linearly accelerating/decelerating or
curvingstorms, only go back 2 or 3 time steps at most whensetting
path Change VCPs to 12 (or 11) when radar becomes active.VCP 12
favors lower elevation scans whereas VCP 11distributes scans more
evenly in the vertical 50. VCP 12 has a 4-1/2 minute volume scan.
You probablyshould require an extra scan before issuing SVR in
amarginal case. Extensive areas of 60 dBZ exceeding 20,000 ft
probablymerit a warning except in tropical air masses The
normalized rotation parameter on GR2 will showvortex-like
structures in strong rotational situations FSI is much more useful
with dual-pol since it willdisplay X-sections of dual-pol data
(unlike GR2) Be wary of along-radial or circular phenomena
(possibleartifact)
