30 June 2009 Severe Weather Outbreak

(Click on any image to see loop or larger image)


This fit into the latest CSTAR research on upper lows by Matt Scolara, most resembling a CSTAR Upper low Neutral Tilt Type A Event


This event was well-anticipated, with the Storm Prediction Center putting our region in the slight risk more than a day in advance. Operational guidance suggested that cooling aloft associated with the slow advance of a neutral tilt upper low, along with an upper impulse rotating around its periphery, would support severe weather in our region. Upper air data and satellite imagery confirmed the existence of these features. Operational guidance also suggested a very diurnal nature to the convection, along the leading edge of cloudiness and a low level theta-e ridge in central and eastern NY during the late morning. The convection would move east through the afternoon, then weaken as the convection moved into New England, where flow off the ocean stabilized the low level atmosphere, and daytime heating subsided toward sunset. Localized flash flooding was possible, even though precipitable water values were not anomalously high, but depended on whether convective lines formed and trained over locations. There was a low level southerly jet segment tracking into the region, with potential moisture advection and convergence that could support not only severe weather but flash flooding.


Storm Prediction Center Upper Air Analyses


500 hPa 300 hPa NAM80 850 hPa winds


Anomalies from 15Z 30 June SREF


Note the MSLP anomalies are 3-4 SD below normal, as are the 500 hPa heights. The 850 hPa V winds were 2-3 SD above normal and the PWAT was around normal.


MSLP 500 hPa 850 hPa PWAT


Satellite loops


Water Vapor Note the upper low tracking across the region, and an upper level impulse was rotating through the region.



Visible loop Note the cyclonic vorticity and broad band of convection



Data and Forecasts


Compare GFS and NAM CAPE forecasts. Both the GFS and NAM showed the larger CAPE values in eastern NY, very diurnally driven. Note the rapid increase in CAPE into the afternoon, and the rapid decrease toward and through the evening.






Observed LAPS CAPE


Loop of the High Resolution WRF predicted composite reflectivity, which made quite a good prediction.



Radar Loops


KENX Loop from 1600-1800 UTC of reflectivity and Severe Thunderstorm Warning Polygons



KENX Loop from 1800-2000 UTC of reflectivity and Severe Thunderstorm Warning Polygons



KENX Loop from 2000-2200 UTC of reflectivity and Severe Thunderstorm Warning Polygons



KENX Loop from 2200-2300 UTC of reflectivity and Severe Thunderstorm Warning Polygons



12Z 30 June Soundings






18Z 30 June Soundings






Storm Prediction Center Outlook



Storm Prediction Center Probabilistic Outlooks for tornadoes, hail and wind




Storm Prediction Center Mesoscale Discussions







Severe Thunderstorm Watch



Albany Area Forecast Discussions









Surrounding Area Forecast Discussions NWS Burlington, VT, NWS Binghamton, NY, and Taunton, MA








Precipitation estimates vs. observed precipitation Did the radar bias cause over estimates of precipitation?



Precipitable Water values were not anomalous, however, with the relatively slow moving lines of thunderstorms, training over the same areas for 1-3 hours, flash flooding was reported in Montgomery County, NY and around Bennington, VT.


Warnings and Severe Weather Reports


Another perspective of severe weather reports for individual NWS offices, courtesy of The Iowa Environmental Mesonet division of Iowa State University Department of Agronomy


NWS Binghamton, NY



NWS Albany, NY



NWS Upton, NY



NWS Taunton, MA



Any questions or suggestions, please e-mail Neil.Stuart@noaa.gov