Friday, June 07, 2013

Andrea landfall and wrap up

We have a unique set of new diagnostic variables for this years experiment in an attempt to extract information about individual hazards. One of those is 0-3km hourly maximum updraft helicity (UH). We decided to add an activity to do tornado probability for the full and 3h periods on Thursday in addition to forecasting the risk in TX in the regular framework.

The results look intriguing. While the 2-5km UH had some pretty robust and long tracks with relatively low max values, the 0-3km UH seemed to highlight very specific regions along the coasts and a brief period of tracks across interior Florida to the right of the Andreas track, with quite a few directly ahead. There appears to be some value and perhaps the HFIP modelers can incorporate these hourly max fields. I guess my recommendation would be to do 0-2km and 2-5km so that overlap is avoided, but given the smoothing inherent in this calculation (WRF has a staggered vertical coordinate so averaging is performed) it may not matter for tracks, but will be important for magnitude.

This is only one case however. These variables were developed to detect supercell structures in the model, and may also be useful in other layers for the winter but still in low topped supercell environments. Testing will continue on ways to continue extracting valuable information from the models.

This will conclude the blogging for this years experiment at least in real time. I hope to continue in some reduced form as we make our way to derive the results of the experiment.

The summary of risk days from the 13z update:
week 1: 4 slight risks.
week 2: 4 slight risks - Granbury and Cleburne tornadoes
week 3: 3 moderate risks, 2 slights - Moore tornado*
week 4: 4 moderate risks, 1 slight - Bennington, El Reno tornadoes
week 5: 4 slight, probably today too

*We also had data for the Shawnee tornado which was a moderate risk on Sunday, May 19.

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