Hurricane Gaston - August 26-September 1, 2004

The genesis of Gaston can be traced to a cold front that moved off the coast of the Carolinas into the
Atlantic on 22 August, and drifted southward the following day before stalling on 24 August.   Surface
observations indicate that a broad low formed along the weakening front on 25 August. Thunderstorm
activity associated with the low remained sporadic and disorganized until late on 26 August, when the
convective activity began to increase and acquire a more banded structure.  Early morning visible and
microwave satellite imagery on 27 August suggest that the low had developed into the seventh tropical
depression of the season by that morning, about 115 n mi east-southeast of Charleston, South Carolina.
It is of note that the frontal zone from which Gaston formed also initiated the development of Tropical
 Storm Hermine two days later.

Steering currents were very weak initially and the depression drifted slowly southward. Convective
banding continued to increase on 27 August and the depression slowly strengthened, becoming a
 tropical storm early the next day as it drifted westward about 130 n mi southeast of Charleston.
 Strengthening continued on 28 August, and the first reconnaissance aircraft to reach the cyclone
 found maximum flight level winds of 67 mph early that afternoon.

Early on 29 August steering currents became better defined, with the development of a mid- to
 upper-level ridge northeast of Gaston and the approach of a mid-latitude trough into the Appalachians.
 This steering pattern allowed the tropical cyclone to begin moving northwestward toward the South
 Carolina coast, and the forward motion of the cyclone increased from about 3 mph to 8 mph overnight
 on the 28/29 August.  Radar and satellite imagery showed that Gaston continued to get better organized
as it approached the coast.   Doppler radar observations indicate that Gaston reached hurricane strength
just before it made landfall near Awendaw, South Carolina, between Charleston and McClellanville,
mid-morning on 29 August, with maximum sustained winds estimated near 75 mph. The tropical
cyclone then steadily weakened while moving northward across northeastern South Carolina.

On the evening of 29 August Gaston weakened to a tropical depression over northeastern South
 Carolina.  Gaston then turned north-northeastward ahead of the trough moving into the eastern United
 States and the cyclone crossed eastern North Carolina and southeastern Virginia during the day.
Data from the Chesapeake Light C-MAN site and a ship near the mouth of Chesapeake Bay
indicated that Gaston had regained tropical storm strength on the evening of 30 August, while the
center was still inland near Yorktown, Virginia.  Tropical storm force winds at this time were
confined to a small area over water southeast of the center; however, the primary impact of Gaston
 in Virginia was flooding produced by 6-12 in rains that occurred over about an 8 h period.

Gaston moved across the southern portion of Chesapeake Bay and crossed the Delmarva Peninsula
 shortly just after midnight on 31 August. The tropical cyclone then accelerated northeastward, passing
about 60 n mi south of Nantucket Island, Massachusetts later that day, as Hermine swung around its
eastern side across southeast Massachusetts. Gaston strengthened slightly as it continued to accelerate to
the east-northeast, before becoming extratropical south of the Canadian Maritimes on the morning of 1
September.  The extratropical remnants of Gaston were finally absorbed by a larger extratropical system
on 3 September about 750 n mi south-southeast of Reykjavik, Iceland. Below is a track of the cyclone
 provided by the National Hurricane Center.

Hurricane Gaston (2004) Track

The storm total rainfall map below was constructed using data from data provided from NWS River
Forecast Centers, as well as additional reports received by the National Hurricane Center.

Gaston (2004) Rainfall Map
Gaston (2004) Filled Contour Rainfall on Black Background
Gaston (2004) Filled Contour Rainfall on White Background

Below are the calendar for Daily Precipitation Maps.  Note that the 24-hour periods end at 12z that morning.

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