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| ProbSevere contours overlaid MRMS Merged Composite Reflectivity, NWS warnings, and local storm reports. |
UW-CIMSS
Friday, August 15, 2014
Crop damage in South Dakota
The morning of August 14th brought a lone hailstorm to central South Dakota. The NOAA/CIMSS ProbSevere model did not detect cloud growth from satellite, as the convection had been ongoing for some time. The MUCAPE and effective shear of the environment were also rather weak. However, the MRMS MESH product reflected the development of the storm, increasing from 0.71" --> 0.97" --> 1.19" --> 1.69" over the span of 6 minutes (14:50 UTC to 14:56 UTC). The probability of severe increased from 14% to 80% during that short time. The MESH soon after was in the 2-3" range (likely an overestimate, possibly owing to single-radar coverage), and hail of up to 1.25" diameter was reported to damage the local corn crop at 15:05 UTC. The model provided 9 minutes of lead-time to the initial hail reports (measured from the 80% threshold). This example demonstrates how crucial radar detection/diagnosis of storms is in the ProbSevere model, as well as to forecasters.
John Cintineo
UW-CIMSS
UW-CIMSS
Monday, August 11, 2014
Satellite growth rate utility in ProbSevere
Convection fired in central Texas along a weak cold front on the afternoon of Monday, August 11th, in an environment characterized by very weak effective bulk shear (< 5 kts) and strong MUCAPE (2800-3600 J/kg).
In the first featured storm, the normalized satellite vertical growth rate went from 'moderate' to 'strong', and the storm-top glaciation rate when form 'weak' to 'moderate' at 17:22 UTC, as the probability of severe jumped from 18% to 61%, with the MESH remaining constant at 0.67 in. The probability then fluctuated between 40% and 60% before the storm was warned at 17:44 UTC with a probability of severe of 58% and MESH = 0.65 in. The fluctuation may have been a result of very low shear and therefore a more "pulse" nature of convection. The satellite growth rates in this storm signaled enhanced probability of severe weather, whereas the shear and MESH were poor to mediocre. This storm was warned again at 18:39 UTC and attained a maximum probability of over 80%. Thus far, there have been no LSRs for this storm, located about 100 miles southeast of Dallas-Fort Worth, TX.
The second featured storm to the southwest had strong normalized satellite vertical growth and glaciation rates at 17:45 UTC. The probability of severe increased from 28% to 72% to 92% from 17:58 UTC -> 18:00 UTC -> 18:08 UTC, as MESH also increased from 0.46 in. to 1.13 in. over that time. This storm was warned at 18:16 UTC and had a severe wind report at 18:18 UTC (trees blocking intersections).
The third storm featured to the northeast of the first storm also had strong satellite growth rates (it was under the same parent satellite cloud-object as the first storm) before rapidly attaining a probability of severe of 86% at 18:56 UTC (MESH = 0.9 in.). It was severe-warned at 19:03 UTC and had a 1 in. hail report at 19:10 UTC.
These examples show how temporal trends in satellite-derived fields can help signal severe potential in slowly developing and more rapidly developing convection. By integrating satellite parameters (when applicable) with radar and NWP fields, we hope to paint a more accurate picture of storm evolution and initial potential severity.
In the first featured storm, the normalized satellite vertical growth rate went from 'moderate' to 'strong', and the storm-top glaciation rate when form 'weak' to 'moderate' at 17:22 UTC, as the probability of severe jumped from 18% to 61%, with the MESH remaining constant at 0.67 in. The probability then fluctuated between 40% and 60% before the storm was warned at 17:44 UTC with a probability of severe of 58% and MESH = 0.65 in. The fluctuation may have been a result of very low shear and therefore a more "pulse" nature of convection. The satellite growth rates in this storm signaled enhanced probability of severe weather, whereas the shear and MESH were poor to mediocre. This storm was warned again at 18:39 UTC and attained a maximum probability of over 80%. Thus far, there have been no LSRs for this storm, located about 100 miles southeast of Dallas-Fort Worth, TX.
The second featured storm to the southwest had strong normalized satellite vertical growth and glaciation rates at 17:45 UTC. The probability of severe increased from 28% to 72% to 92% from 17:58 UTC -> 18:00 UTC -> 18:08 UTC, as MESH also increased from 0.46 in. to 1.13 in. over that time. This storm was warned at 18:16 UTC and had a severe wind report at 18:18 UTC (trees blocking intersections).
The third storm featured to the northeast of the first storm also had strong satellite growth rates (it was under the same parent satellite cloud-object as the first storm) before rapidly attaining a probability of severe of 86% at 18:56 UTC (MESH = 0.9 in.). It was severe-warned at 19:03 UTC and had a 1 in. hail report at 19:10 UTC.
These examples show how temporal trends in satellite-derived fields can help signal severe potential in slowly developing and more rapidly developing convection. By integrating satellite parameters (when applicable) with radar and NWP fields, we hope to paint a more accurate picture of storm evolution and initial potential severity.
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| ProbSevere contours around MRMS merged composite reflectivity. |
EDIT: Several of these storms did have marginal wind and hail reports.
John Cintineo
UW-CIMSS
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