Hurricane Bob (1979)

Meteorological history

The origin of Hurricane Bob can be traced to a tropical wave that was first located near Cape Verde towards the end of June. The disturbance tracked westward with minimal signs of development, and reached the northwestern Caribbean Sea on July 6. The following day, the tropical system tracked across the Yucatán Peninsula the following day, and upon emerging into the Gulf of Mexico, the cluster of storms began to develop a weak circulation center. This enabled for more rapid tropical cyclogenesis, and at 1200 UTC on July 9, the disturbance was analyzed to have organized into a tropical depression – the third of such in the Atlantic that year. The depression strengthened rather quickly, and on the morning of July 10 a United States Air Force reconnaissance flight indicated that the tropical cyclone had strengthened to tropical storm intensity while situated 740 mi south of Louisiana. At the time the flight measured a minimum barometric pressure of 998 mbar (hPa; 29.47 inHg).

Upon reaching tropical storm intensity, Bob began to curve further northward as opposed to its prior, northeasterly track, due to the presence of a strengthening, upper-level trough to the storm's west. The trough greatly enhanced atmospheric conditions around Bob, allowing for the tropical cyclone to intensify rapidly. Though the hurricane's maximum sustained winds would hold steady at 75 mph for approximately the ensuing twelve hours, the storm's barometric pressure would fluctuate before reaching a minimum of 981 mbar (hPa; 28.98 inHg) at 1200 UTC that day; this would be Bob's lowest documented barometric pressure. At around the same time, the hurricane made landfall west of Grand Isle, Louisiana. After moving inland, Bob quickly weakened due to land interaction, and was a mere tropical depression by July 12. However, the resulting depression would maintain its intensity for the next several days. On July 13, the low-pressure area drifted into southern Ohio and afterwards curved eastward. On July 16, Bob's remnants moved into the western Atlantic, where they were subsequently absorbed by another low-pressure area.

Preparations

As Bob moved towards the U.S. Gulf Coast, the National Weather Service issued gale warnings for coastal regions extending from Vermilion Bay, Louisiana to Biloxi, Mississippi at 1600 UTC on July 10. These warnings were upgraded to hurricane warnings upon Bob's strengthening to such an intensity. During the storm's existence, forecasts and predictions from the National Hurricane Center were of greater accuracy than on average.

In preparation for the storm, 8,000 offshore oil workers were evacuated. On land, 2,500 residents and tourists on Grand Isle were also evacuated.

Impact

Effects in the United States as a result of Bob were typical of a minimal hurricane, and were not of considerable nature. At the coast, Bob caused moderate storm surge, resulting in coastal waters rising to as high as 5 ft above normal. The rough seas sunk several boats and caused significant damage to piers. A levee on Grand Isle was breached by the surge, resulting in some coastal inundation. Minor beach erosion occurred on the coast of Mississippi. In Mobile County, Alabama, the wave action damaged cars near the shore and disrupted seafood operations in the Bayou La Batre area.

Strong winds were reported in association with the storm, but no station documented sustained winds within hurricane force. The highest wind observation was taken on an oil rig off the coast of Louisiana, which clocked sustained winds at 63 mph. However, the strongest wind gust in association with the hurricane was measured in Bay St. Louis, Mississippi, at 64 mph. In addition, widespread power outages impacted 53,000 electricity customers in the city's area. Similar incidents took place in Houma, Louisiana. In Lafitte, Louisiana, two men were blown off of the roof of a marina, and one of them was killed; this would be the only death associated with the hurricane. Further east, in Florida, trees and power lines were downed in Niceville.

Hurricane Bob also produced a widespread area of rain that was heavy in localized areas. Rainfall associated with the hurricane peaked at 7.16 in in Louisiana, where the storm made landfall. Statewide rainfall totals peaked at 6.64 and in Pascagoula, Mississippi and Robertsdale, Alabama, respectively. Further inland, the remnants of Bob dropped heavy rainfall in the Midwestern United States, peaking at 5.72 in at a station in Indiana University Bloomington. In addition to the strong winds and heavy rain, Bob produced eight tornadoes across the southern United States. One of these tornadoes caused $27,500 in damage after striking areas of Biloxi, Mississippi. Overall, Hurricane Bob caused approximately $20 million in damage. However, $15 million in damage resulted from flooding in Indiana, with the rest of the storm's monetary impacts arising from coastal regions.

Notes

References

References

1. National Hurricane Center. "Preliminary Report for Hurricane Bob, Page 1". United States National Oceanic and Atmospheric Administration.
2. Schmid, Randolph E.. (May 27, 1979). "Men to Share Hurricane Blame". Palm Beach Post-Times.
3. (July 12, 1979). "Severe Weather Kills 1, Injures 4". Florence Times Daily.
4. (July 11, 1979). "Hurricane Bob Is First of the Season". Pittsburgh Post-Gazette.
5. (July 11, 1979). "Hurricane Bob Aims For Louisiana". Daytona Beach Morning Journal.
6. Roth, David M.. "Hurricane Bob - July 9-16, 1979". United States National Oceanic and Atmospheric Administration's Weather Prediction Center.
7. Roth, David M.. "Tropical Cyclone Rainfall for the Gulf Coast". United States National Oceanic and Atmospheric Administration's Weather Prediction Center.
8. Roth, David M.. "Tropical Cyclone Rainfall for the Midwest". United States National Oceanic and Atmospheric Administration's Weather Prediction Center.