By the 27th , both circulations were generating deep convection a few hundred miles to the northeast of the Leeward Islands. A day later, meteorologists at the NHC Tropical Analysis and Forecast Branch (TAFB) and the NESDIS Synoptic Analysis Branch (SAB) assigned Dvorak technique T-numbers of 1.5 to the trailing cloud cluster. These numbers increased to T-2.5, potentially indicative of a tropical cyclone with 35 knot (tropical storm force) winds by midday on the 30th. In reality, although the cloud pattern was slowly consolidating and surface pressures were falling ahead of the system in the Bahamas, development was retarded by southwesterly vertical wind shear associated with an upper-level low that was moving southwestward at 10-15 knots across Florida. Reconnaissance aircraft data from the U. S. Air Force Reserves (Hurricane Hunters) on the 28th, 29th, and again during midday on the 30th indicated that the system did not have a closed circulation at low levels. Instead it was a very vigorous tropical wave -- wind speeds around 40 knots were reported from ships in the northern part of the cloud pattern.
Because of the system's potential for development and its close proximity to the Bahamas and Florida, a special nighttime reconnaissance mission was requested by the NHC and flown by the Hurricane Hunters late on the 30th. The first "vortex message" was transmitted to the NHC shortly after 0100 UTC on the 31st. From that information it is estimated that the system became Tropical Storm Erin at 0000 UTC on the 31st.
The upper-level low near Florida affected Erin's movement and development. Associated steering currents accelerated Erin from 5 to 15 knots and diverted the cyclone around the northeast side of the low. The temporary and fairly subtle change of heading from west-northwest to northwest might have been insignificant if Erin had not been so close to land. Instead, the track of the center was deflected to a course that was over or near much of the Bahama Island chain and then toward landfall over east-central (rather than southeast) Florida. As this occurred, enough shearing persisted to permit only slow strengthening. On the evening of the 31st, Erin became a hurricane while centered near Rum Cay in the Bahamas. A ragged-looking eye appeared on satellite pictures on August 1st. Erin made landfall around 0600 UTC on the 2nd near Vero Beach, Florida as a Category 1 hurricane on the Saffir/Simpson Hurricane Scale, with estimated maximum one-minute wind speeds of 75 knots.
Erin's track bent back to west-northwest while the cyclone crossed the Florida peninsula during the morning and early afternoon of the 2nd. The cyclone weakened to a tropical storm with 50-knot winds during that period, but remained well-organized. Upon emerging into the eastern Gulf of Mexico, Erin reintensified on a track that gradually swung back to northwestward at about 10 knots. Final landfall occurred near Pensacola, Florida during the late morning of the 3rd. An eye had redeveloped but upper-level outflow was not particularly impressive on satellite images. Erin had around 85 knot winds (category 2) in a small area of its northeastern eyewall when that part of the hurricane came ashore near Fort Walton Beach in the western Florida panhandle.
Erin weakened to a tropical storm in southeastern Mississippi overnight on the 3rd/4th. It was a tropical depression when its track shifted to the north on the 5th and the east on the 6th. The depression merged with a frontal system over West Virginia on the 6th.
Several reports of hurricane force winds (WMO-standard 10-minute average) were received from the Bahamas, including 68 and 70 knots during the passage of the northeast part of the eyewall over Cat Island at 0200 UTC and 0400 UTC, respectively, on August 1st. These 10-min winds are about 80 percent of the 86 knot maximum 10-second 850 mb flight-level winds encountered by the reconnaissance aircraft. Several amateur radio reports included gusts to around 90 knots in the Bahamas. The ship Tampa was in the northeastern eyewall at 1200 UTC on the 1st when it reported 70 knot winds.
The basis for the 75-knot wind speed estimate along the Florida east coast was a one-minute wind speed of 74.6 knots recorded by a Florida Institute of Technology anemometer which made one observation per hour at Sebastian Inlet. This wind appears to coincide with the passage of one of Erin's strongest convective cells at that time (0500 UTC), which was located in the northwestern eyewall. While somewhat higher winds could have been expected to occur offshore in the (normally stronger) northeastern eyewall, Doppler radar data for that area suggest that the peak winds (inbound toward Melbourne) at the lowest tilt angle were only slightly stronger, around 85 knots. The maximum 850 mb flight-level wind speed then was around 85 knots.
A wind speed of 85 knots is estimated at 1330 UTC on 3 August near Fort Walton Beach. This took place in a small area within Erin's strongest sector, the northeastern eyewall, as it swept across the shoreline. That estimate is based largely on NWS Mobile office Doppler wind data which showed inbound wind speeds exceeding 100 knots in a few volume samples centered at about 9800 feet above the coast from 1320 to 1400 UTC. The peak 850 mb flight-level wind speed leading up to this time was 92 knots in the northeastern eyewall near 1200 UTC, but subsequent excursions into that part of the hurricane were precluded by the hurricane's close proximity to land.
Doppler velocities decreased by about 15 knots over the following two hours and 75 knots is the estimated maximum surface wind speed when the center of the eye came ashore around 1600 UTC. Hence, the coastal region immediately west of Fort Walton Beach, including Pensacola, experienced Category 1 conditions, though gusts to near 100 knots likely occurred. The FAA system of six anemometers at Pensacola Regional Airport (PNS) registered a maximum 30-second wind speed of about 60 knots. The highest wind speed measured at an official reporting station in the Florida panhandle was an 88 knot gust at the Pensacola Naval Air Station (NPA). Amateur radio operators relayed unofficial observations of gusts near 95 knots to the NHC.
The hurricane's lowest pressure of 973 mb was reported by the Hurricane Hunters near 1330 UTC and again near 1600 UTC on the 3rd. The latter measurement placed the center of Erin near the coast and in the southern part of the eye as seen on surface radar.
The Melbourne National Weather Service Office estimated that Erin generated a 2 to 4 foot storm tide during the Florida east coast landfall. Storm tides averaged 1 to 2 feet along the west-central Florida peninsula. According to the Melbourne office, up to about 12 inches of rain fell southwest through northwest of their site. Several small, brief tornadoes occurred over east-central Florida well after Erin made landfall. One tornado caused minor damage in Titusville. Another occurred near Lake Lizzie, killing two horses. A couple of weak tornadoes were also reported over northeast Florida and in the panhandle near Hurlburt Air Force Base.
Storm tides were estimated at 6 to 7 feet just west of Navarre Beach and 3 to 4 feet along Pensacola Beach. Up to 5 inches of rain was reported from the panhandle.
All Bahamas islands from Mayaguana to Grand Bahama suffered damage characterized by the Bahamas Department of Meteorology a mostly minor. Some structural damage, sunken boats, crop loss, and flooding was reported. Losses known to date for Abaco, Grand Bahama, Mayaguana, and Exuma total $400,000.
The American Insurance Services Group estimated $375 million as the loss to insured property in the United States caused by Erin ($350 million in Florida, $20 million in Alabama, and $5 million in Mississippi). Because the total loss is usually estimated by the NHC to be up to about double the insured loss, the total U. S. loss is tentatively estimated at $700 million.
Wind damage occurred over east-central and northeast Florida. Thousands of homes and businesses suffered damage in Brevard County. Less significant damage occurred in other counties in the region. Freshwater flooding from rainfall occurred in the Melbourne and Palm Bay areas and westward in some spots to the Florida gulf coast. Beach erosion occurred along the central Florida east coast, with damage mainly to boardwalks, beach accessways and the dune system. Light to moderate beach erosion was also reported northward to the Georgia border. Minor erosion occurred along the west-central Florida coast.
The most significant structural damage for the final landfall occurred on Pensacola Beach, Navarre Beach, around Mary Esther and in northeast Pensacola. More than 2000 homes were damaged there and crop losses were reported. Some beach erosion was reported west of Navarre Beach. Farther inland, about 100 homes were damaged in Alabama. Widespread tree, power line and crop damage extended inland.