What s New in the NWS? Georgia Association of Floodplain Management Lans P. Rothfusz Meteorologist in Charge Peachtree City, GA 27 March 2012
Overview Summer Outlook Radar future is here! CoCoRAHS Appeal for river gauges
Spring Outlook La Nina declining to ENSO-neutral. Apr-Jun Temperature Apr-Jun Precip Slightly better-than-equal chances of warmer. Equal chances of wetter/drier/normal.
DUAL-POLARIZATION UPGRADE
Radar Yesterday/Today
Radar 2020 (Dual-Polarization)
Dual-Pol Advantages Improvement in radar data quality. More accurate rainfall estimation*. Differentiates between particle types. Meteorological = rain, snow, hail, sleet Non-Meteorological = birds, dust, insects and DEBRIS! *Maybe...
Correlation Coefficient (CC) Definition: Measure of similarly between horizontal and vertical pulses within a volume. Application: Helps determine if hydrometeors have the same shape and type, or if more of a mixture exists Non-Meteorological Birds, insects, etc Complex scattering from pulse to pulse Low CC (<0.7) Meteorological (Non-Uniform) Hail, Wet Aggregates (melting snow) Somewhat complex scattering from pulse to pulse Moderate CC (0.80 to 0.97) Meteorological (Uniform) Rain, Snow, etc Consistent scattering from pulse to pulse High CC (>0.97)
CC - Non-Met vs. Met Echoes Areas of noisy CC less than 0.85 most likely indicate non-precipitation echoes.
CC Rain vs. Snow When CC is added to reflectivity and observations, it becomes apparent where the transition from rain to snow is occurring.
CC Significant Severe Hail Hail >1 will have significantly reduced correlation coefficient CC 0.8 associated with hail golf ball size
CC Tornadic Debris Within 75 km (~45 mi), lofted debris is noted by a significant drop in CC.
Differential Reflectivity Definition: difference between the horizontal and vertical reflectivity factors. Application: helps identify the dominant target shape. Spherical Horizontally Oriented Vertically Oriented Drizzle, Small Hail, etc Rain, Melting Hail, etc Vertically Oriented Ice Crystals Z H ~ Z V Z H Z V ~ 0 Z H > Z V Z H Z V > 0 Z H < Z V Z H Z V < 0 ZDR ~ 0 db ZDR is positive ZDR is negative
ZDR Rain The strong relationship between raindrop diameter and shape leads to a nice relationship between major axis diameter and ZDR value. Major Axis Diameter (mm) Image ZDR (db) < 0.3 mm ~ 0.0 db 1.35 mm ~ 1.3 db 1.75 mm ~ 1.9 db 2.65 mm ~ 2.8 db 2.90 mm ~ 3.3 db 3.68 mm ~ 4.1 db 4.00 mm ~ 4.5 db
ZDR Hail Detection Look for high reflectivity values and low ZDR.
ZDR Rain/Snow Transition Area Rain/Snow transition more obvious in ZDR. ZDR in rain generally > 1dB ZDR in snow typically < 0.5 db
KDP - Applications Heavy rain only Heavy rain mixed with hail Cold vs. warm rain processes
KDP Heavy Rain Only Primary advantage is its ability to detect heavy rain situations Use KDP to highlight areas of heavier rainfall
KDP Rain, Hail and Mixed Precip Rain: Z: high ZDR: high, + KDP: >1 deg / km Hail, little rain: Z: high ZDR: slightly + KDP: near 0 Mixed Precip: Z: high ZDR: high, + KDP: very high
22 December 2011 Tornadoes
22 December 2011 Tornadoes Rome, GA Calhoun, GA Moreland, GA Fayetteville, GA Brooks, GA
22 December 2011 Tornadoes Traditional Radar Data Reflectivity
22 December 2011 Tornadoes Traditional Radar Data Storm-relative velocity Tornadoes occurred at 2244Z (Moreland) 2316Z (Brooks) 2318Z (Fayetteville)
22 December 2011 Tornadoes Dual-Polarized Radar Data Correlation Coefficient Tornadoes occurred at 2244Z (Moreland) 2316Z (Brooks) 2318Z (Fayetteville) Note lag from tornado to debris
2 March 2012 Tornado Haralson and Paulding Counties
2 March 2012 Tornado
CoCoRAHS Community Collaborative Rainfall, Hail and Snow network Volunteer observers. Data collected daily (and instantly, for severe). Improves our hydrologic response. www.cocorahs.org
River Gauges Crucial to our forecasting success. Beneficial to you. More is always better! USGS and NWS need you and your data! September 2009 Georgia Flooding
Civil Emergency Messages New approach to epic flooding events (only). In coordination with EMs. In conjunction with standard Flood Warnings. September 2009 Georgia Flooding
Questions? Lans P. Rothfusz lans.rothfusz@noaa.gov 770-486-1133 x222