Convective Initiation Studies at UW-CIMSSK. Bedka (SSAI/NASA LaRC), W. Feltz (UW-CIMSS), J. Sieglaff (UW-CIMSS), L. Cronce (UW-CIMSS)

Objectives• Develop day/night convective initiation nowcast methodology for use with GOES-12, MSG SEVIRI, and future GOES-R ABI imagery based on a box-average approach

• Explore cloud object tracking methods to facilitate product validation and improve convective initiation nowcasting especially for rapidly moving clouds

Accomplishments• UW-CIMSS CI nowcast product suite (UWCI) was evaluated within the NOAA Storm Prediction Center Spring Experiment. UWCI was one set of products supplied by the GOES-R Proving Ground to SPC

• Completed UWCI validation with MSG SEVIRI study using cloud-to-ground lightning data over South Africa

• GOES-12, MSG SEVIRI, and synthetic GOES-R imagery has been processed within the Warning Decision Support System-Integrated Information (WDSS-II) to investigate the applicability of this system for current and future CI nowcast activities. NOAA recently approved 2 years of funding for continuing work on this effort

UWCI Box-Average Nowcast Product Description

• Current and future imagers are operating in 5-min rapid scan, so cumulus do not move very far between images

- For 50 CI cases over CONUS, average cloud movement=5 km/5 mins, 1 SD=2 km/5 mins

• One can disregard cloud motions by time-differencing “box-averaged” cloud top properties to determine CI

• Compute mean IRW BT for cloud categories identified by day/night cloud type product over 7x7 and 14x14 pixel SEVIRI IR pixel boxes

• Employ rules to eliminate situations where cirrus anvil moves into box with developing cumulus

• Compute cloud-top cooling rate, minimum threshold at -4 K/15 mins

• Use mesoscale NWP stability analysis to minimize CI nowcast false alarm from cooling of non-convective cloud. Most unstable LI used to capture surface-based and/or elevated storms

• Use cloud typing information with cooling rates to further minimize false alarms and develop confidence indicators for convective initiation

- Filter out isolated noisy nowcast pixels- Cat 1: Cooling liquid water clouds- Cat 2: Cooling supercooled/mixed phase- Cat 3: Cooling with recent transition to thick ice cloud

• Though the method is optimized for 5-minute imagery, the examples and validation to the left show results when applied to 15-minute SEVIRI imagery

M. Pavolonis (NOAA/NESDIS) Day/Night Cloud Microphysical Typing

15-Min Cloud Top Cooling CI Nowcast Using 15-min Data

45-min Accumulated Cooling 45-min Accumulated CI Nowcast

Channel 9 BT At End Of 45-min Period

Channel 9 BT 1 Hour Later

SEVIRI Channel 9 IR Window BT

Lightning Initiation POD (133 LI cases): 76%Lightning Nowcast FAR (10214 pixels): 29%Lead time decreases with cloud glaciation

Product Validation

UW-CIMSS Participation in NOAA Storm Prediction Center Spring Experiment: UWCI Product Evaluation

20090508 Time Accumulated Cloud Top Cooling Rate Animation

• A current CI nowcast method (Mecikalski and Bedka (MWR, 2006)) has focused on the use of visible imagery to objectively identify cumulus clouds and compute cloud motions, rendering this a daytime only product

• The UWCI nowcast product suite has been applied to GOES-12 imagery, as the Pavolonis cloud microphysical typing (submitted to JAS, 2009) can operate during day and night despite the more limited spectral information from current GOES

• The UWCI products were evaluated at SPC over a 1 month period as part of the GOES-R Proving Ground (see Chris Siewert), since the UWCI represents an algorithm that will have optimal performance in the GOES-R era

- Products are also being evaluated at a local National Weather Service (NWS) office and NOAA/NESDIS

• Through these evaluations, the UWCI has been shown perform quite well, offering significant advantages in 1) day/night coverage, 2) processing speed, and 3) product spatial coherency/accuracy over current multiple interest field daytime-only methods

• Limitations and weaknesses of UWCI product suite:•Thin cirrus moving over small cumulus and expanding anvil edge can induce false alarm

•Product limited to 15-min or better resolution imagery•Little to no CI nowcast lead time in very moist, weakly capped environments. This is a likely issue with any IR-based CI nowcast product

• Contact Wayne Feltz (waynef@ssec.wisc.edu) for detailed information on UWCI algorithm applications

Exploring the Use of Object Tracking for CI Nowcasting• UW-CIMSS and the University of Alabama in Huntsville (UAH) are working toward development of object-

based methods for CI nowcasting in the GOES-R ABI era, using current GOES-12 and MSG SEVIRI as proxies for GOES-R

• UW-CIMSS is experimenting with the Warning Decision Support System-Integrated Information (WDSS-II, Lakshmanan et al. (J. Tech., 2009), (WAF, 2007)) to compute cloud-top cooling rates and cloud-top microphysical trends to produce object based CI nowcasts

• WDSS-II can handle non-overlapping clouds and can project object locations into the future

• Radar reflectivity can be remapped to the satellite resolution/projection and carried along with the satellite-derived objects for reliable product validation

• This capability is not available with current pixel-based CI nowcast methods which causes significant difficulty in evaluating current product accuracy over large scenes and numerous cases

MSG SEVIRI Example

GOES-12 Example