*Note that this website is an expanded version of the paper Stuart et al. (1998) in the Pre-print volume of the 19th Conference on Severe Local Storms, to be presented in Minneapolis, Minnesota during the week of September 14-18, 1998.


Here are the two lightning images that prompted our study, courtesy of Global Atmospherics.

Note the maxima around Hampton Roads for both time periods (click on images to enlarge).


Before we look at some individual cases, there are some important points that must be considered: (click to enlarge)

Additional notes to Important Considerations


Another important consideration:

What if there are more thunderstorms annually in Norfolk, compared to, say, Richmond, then wouldn't that account for some of the increased lightning activity in Hampton Roads? Hopefully, these 2 graphs will help answer that question (click to enlarge):



We evaluated KAKQ VAD Wind Profile (VWP) data in order to categorize the lightning events by mean wind flow. The three main categories are:

The three categories were subdivided since many events were combinations of more than one type, as can be seen in this chart:
 
W to NW Deep Flow Weak Deep Flow SW Dynamic Flow Combo of W to NW and Weak LLVL Flow Combo of SW and Weak LLVL Flow SW Deep Flow with Multiple Lines of Storms
6/24-25/96 

7/18-19/96 

7/22-23/97 

6/19-21/96 

8/24-25/96 

5/6/96 

7/10-11/95 

7/21-22/95 

7/21-22/97 

7/19-20/97 

7/18/97 

7/3-4/96 

8/4/97 

8/20-21/97 

7/22-23/96 

8/16-17/96 

3/15-16/96 

6/25-26/96

7/16-17/97 

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7/25-26/96 

7/19-20/97 

8/25-28/96 

8/16-17/96 

7/4-5/95 

6/25-26/96 

9/7-9/96

7/31-8/2/96 

6/26-27/97 

6/12-13/96 

9/1-2/95 

7/15-16/96 

6/11-12/96 

5/1-2/97 

6/11-13/95 

7/14/96 

8/24-25/96 

7/19-20/97 

7/18/97 

7/22-23/96 

8/16-17/96 

6/25-26/96

7/16-17/97 

7/25-26/96 

8/25-28/96 

9/7-9/96

7/21-22/95 

7/15-16/96 

6/11-13/95 


Now, here are a few cases (click on images to enlarge).

June 24, 1996 - This was our number 1 lightning event with over 25,000 lightning strikes in roughly 18 hours. Important points:

From left to right, these are Base Reflectivity, Composite Reflectivity and VAD Wind Profile Studies have shown (Dye 1990) that collision of frozen particles in thunderstorms, such as hail, contributes most to charge separation within thunderstorms. The widespread hail that occurred in this event, suggests that the collision process may have contributed to enhanced charge separations and higher frequency of lightning.


July 18, 1997- Over 3,600 lightning strikes occurred in roughly 5 hours. Important points:

From left to right, these are Base Reflectivity, Composite Reflectivity and VAD Wind Profile Intersecting boundaries can initiate, and may possibly enhance thunderstorm updrafts (Bluestein 1993) A remarkable number of weak flow cases illustrated these intersecting boundaries to varying degrees. Most were similar to this case, where the boundries were difficult to see, but their presence was enough to see the intersection of the boundies in the area of the 4 and 7 year lightning maxima. The multiple cases of intersecting boundaries suggested to us that during weak flow regimes, these boundaries are often present, and the intersection may enhance thunderstorm updrafts in the area of the 4 and 7 year lightning maxima.


May 30, 1998 - Not a part of the 1994-1997 data set but best depicted the local boundaries often present during weak flow regimes

From left to right, these are Base Reflectivity and VAD Wind Profile Intersecting boundaries can initiate and possibly enhance thunderstorm updrafts (Bluestein 1993) This case best depicts a "James River Boundary", which isn't always depicted since it often is hidden in ground clutter. As mentioned before, in many weak flow regimes, the presence of intersecting boundaries, one being a "James River Boundary", is present to varying degrees, and may enhance thunderstorm updrafts in the area of the 4 and 7 year lightning maxima.


July 31, 1996 - Over 10,000 lightning strikes occurred in roughly 34 hours. Important points:

From left to right, these are Base Reflectivity, Composite Reflectivity and VAD Wind Profile In general, southwest flow events produced the least amount of lightning compared to other categories, although the more dynamic events were the ones that made our list, with this case our number 1 southwest flow event. This event was characterized by outflow boundaries intersecting with the moisture streets. As stated previously, intersecting boundaries can enhance thunderstorm updrafts and result in more frequent lightning.

Southwest flow events were usually characterized by pre-frontal lines of convection, but only the dynamic southwest flow events produced enough lightning to be included in our study. The multiple lines of convection likely contributed to the overall lightning frequency in any area during any particular southwest flow event.


So what did we learn, what benefits do we expect from this study, and what are our prospects for future research?

From left to right: Preliminary Conclusions, Benefits to NWS Wakefield, Benefits to Virginia Power, and Future Research (click to enlarge)


References


Comments and suggestions please e-mail Neil Stuart

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