w2accumulator applies MHT faster

One of the best ways to improve the quality of the Rotation Tracks products is to apply spatial QC using hysteresis and temporal QC using Multiple Hypothesis Tracking.

Unfortunately, this used to be quite slow. An hour of azimuthal shear data covering the CONUS could take as much as two hours to process. Therefore, it was used only in research studies and off-line, but not to produce the post-event rotation tracks that you can download from http://ondemand.nssl.noaa.gov/

w2accumulator’s -Q option now supports two vastly more efficient optimizations. You can specify that the number of hypothesis is 1 (meaning to only keep the best track, and not bother about second-best, third-best, etc.) or that the algorithm should retain all potential tracks (specifying -1 for number of hypotheses).  These are the most likely values that you will want to specify and with these, the algorithm runs 20x faster.  Yup, you can now process an hour of data in about 6 minutes.

Method -Q option CPU Time (microseconds)
No QC ” “ 46
5 best blob:0.002:0.005:2:azshear,mht:1:2:1800:5:5 2046
Only best blob:0.002:0.005:2:azshear,mht:1:2:1800:5:1 132
All reasonable blob:0.002:0.005:2:azshear,mht:1:2:1800:5:-1 138

You used to have only the first two options for -Q available. Now, you have two more, and these two “special” values are highly optimized.

What’s the impact of these options? (Open the images in different tabs in your browser and switch between them so that you can see the differences between the last two images more readily)

Azimuthal shear field without QC
Keeping only best hypothesis
Keeping only best hypothesis
Keep all reasonable hypotheses
Keep all reasonable hypotheses

For more details about MHT-QC and its application to rotation tracks products, please see these scientific articles:

M. Miller, V. Lakshmanan, and T. Smith, “An automated method for depicting mesocyclone paths and intensities,” Wea. Forecasting, vol. 28, pp. 570-585, 2013.

V. Lakshmanan, M. Miller, and T. Smith, “Quality control of accumulated fields by applying spatial and temporal constraints,” J. Atmos. Ocean. Tech., vol. 30, pp. 745-757, 2013.