TROPICS COME CALLING

After a slow start to the 2004 hurricane season, the middle part of August through September proved to be quite busy with the formation of 10 tropical cyclones in the Atlantic. Four of these systems, or the remnants there of, directly impacted the Blacksburg county warning area. These included Gaston, Frances, Ivan, and Jeanne (Fig. 1) which all affected the region over a month long period between August 28^th and September 28^th.

Tropical Storm Gaston had the least impact as it tracked into eastern Virginia and offshore toward the end of August. It caused minor flooding problems across the piedmont sections of Virginia where 1 to 4 inches of rain fell.

Frances and Ivan were more impressive major hurricanes that originated off the Cape Verde islands and made the long trek into the Gulf of Mexico during early and mid September. After making a final landfall on the Gulf Coast, these storms moved northeast along the spine of the Appalachians before dissipating. Both were prolific rain producers with maximum average amounts of 6 to 10 inches with Frances, and 3 to 6 inch totals along the Blue Ridge southwest of Roanoke near Ivans track. However dry soil conditions limited widespread flooding except over the northwest North Carolina mountains where moderate to severe flooding was observed in some locales. Tornadoes spawned from Ivans remnants were the bigger story as several spinups caused structural and tree damage across the foothill and piedmont sections on the 17^th of September.

Jeanne followed in close pursuit of Ivan in late September as its low pressure remnant worked north from the Gulf of Mexico and along the southern portions of the Blue Ridge. This system caused flooding of most main stem rivers as well as severe small stream and creek flooding. Locations again along the Blue Ridge saw the heaviest rainfall amounts of 6 to 10 inches. This caused major flooding in the city of Roanoke as the Roanoke River rose to about 8 feet above flood stage. An isolated tornado also associated with Jeannes rainbands skipped through parts of southside Virginia during the early morning hours of September 28^th. It too produced more tree and mobile home damage northwest of Danville.

So far the 2004 tropical weather season, with 12 named storms, 7 of which were hurricanes, and 6 major storms, is above the seasonal average of 10 named systems and 2 intense hurricanes. This is also about 220% of the full hurricane season average which ends on November 30^th. The outlook for the remainder of October into November calls for the possibility of another named storm or two, while climatology suggests that the threat to the U.S. mainland quickly decreases by November as cooler autumn air invades.

Fig 1. Tracks of Frances, Gaston, Ivan, and Jeanne.