I'll start off by saying feel free to add your comments or questions to these weather stories. I had a question come up a couple weeks ago that sparked my interest and spawned this week's World of Weather: Sherman H. “Is there any correlation to these dry spring/summer periods and wet/tropical storm periods later in the same year?”
It’s a very good question and certainly something worth looking into. La Nina is a huge climate player in the Pacific and when she is kicking her influences can reach all across the globe. As we know, La Nina is a time when the Pacific is cooler than average. In our case, we are in a weakening La Nina period, but there is some good indication we will be heading back into a La Nina for the fall season. Below I’ve taken the years of extreme drought conditions and matched them up with the tropical activity for that time period. The results are rather interesting:
10 Storms, 3 US landfalls, 1 NC landfall
May & June rainfall: 6.97"
Tropical Depression 8- Mid October, Came across eastern NC as an extra tropical storm system
12 Storms, 5 US landfalls, 3 NC landfalls
May & June rainfall: 7.85"
Cat 3 Connie- Resulted in massive flooding (August 3rd)
Cat 1 Diane- 5 days after Connie, more unwanted rain (August 7th)
Cat 3 Iona- Weaker storm (September 10th)
10 Storms, 8 US landfalls, 2 NC landfalls
May & June rainfall: 4.63"
Cat 3 Gloria- 900 Million dollars in damage. Skirted the Cape Hatteras coast (September 16th)
T.S. Kate- After a long track through the Florida and Georgia, Kate brought heavy rain to eastern NC (November 15th)
6 Storms, 3 US landfalls, 1 NC landfall
May & June rainfall: 6.67"
Hurricane Charlie- Made landfall in Florida, but strengthened back over the Atlantic. Made landfall near Cape Lookout (August 13th)
16 Storms, 7 US landfalls, ~2 NC landfalls
May & June rainfall: 4.27
Tropical Storm Cristobal- Spun up off the coast of Georgia. While the eye never came over North Carolina real estate, rain could be felt through the Outer Banks and Cape Lookout (July 19th).
Tropical Storm Hanna- Came ashore near Wilmington and road up I95. A lot of rain but weak winds accompanied her (August 28th).
There seems to be a nice correlation between extreme droughts in the east and tropical activity. In that, anytime we've experienced a very noticeable rainfall deficit, a tropical system has helped bring us back closer to our yearly rainfall average...and in some cases more. This is clearly visible in the "NC Landfalls" category. All the dates listed have had at least one tropical system come through during the hurricane season. Pretty interesting.
Keep in mind that this was a very broad look at the drought conditions and the Atlantic hurricane season. In fact, these drought years miss most of our strongest and worst hurricanes (i.e. 1999). Basically what I’m trying to say is, take this data lightly and try to avoid drawing extreme conclusions like “we’re guaranteed to see a tropical storm this year”. Instead, use this data to help highlight some of the interesting aspects of our North Carolina climate. We'll continue to watch the tropics closely and maybe by the end of this season we'll have one more data point to add to this trend.
For the months of May & June, the combined rainfall totals should be ~9".
La Nina Years: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml
Rainfall Data: http://www.nc-climate.ncsu.edu/climate/climdiv.php