A tropical wave moved from Africa to the Atlantic Ocean on 4 October accompanied by a large cyclonic rotation of low clouds and a mid-tropospheric jet. The wave moved westward under an unfavorable strong vertical shear environment and, on 11 October, passed through the Windward Islands where a marked wind shift and large 24-hour pressure changes were observed. It reached the southwestern Caribbean on the 13th, where a pre-existing area of low surface pressure was located.
The system developed a well-defined low-level circulation and became a tropical depression at about 1200 UTC on the 14th, just east of Nicaragua, and began moving northwestward at about eight knots.
Over the next two days, the depression turned north and the north-northeastward in response to a weak mid- to upper-level low over the Gulf of Mexico. Although there appeared to be considerable convective banding and falling surface pressures, aircraft data showed that the depression did not strengthen to a storm until early on the 16th, when the center was close to Swan Island. With a well-established outflow over the circulation, Lili strengthened to a hurricane on the 17th.
Moving slowly, the center executed a small cyclonic loop just north of Swan Island on the 16th and wobbled again on the 17th as it approached the Isle of Youth, Cuba. The center passed over the eastern side of the Isle of Youth near 0100 UTC on the 18th and made landfall on the south coast of mainland Cuba in Matanzas Province at 0930 UTC. The maximum sustained surface winds had strengthened to near 85 knots at landfall as Lili turned eastward for a twelve-hour crossing of central Cuba on the 18th.
A major trough in the westerlies moved to the eastern United States as Lili approached Cuba and this resulted in the hurricane accelerating mostly northeastward to a forward speed of near 25 knots by late on the 19th.
The hurricane maintained its strength over Cuba. The pressure was measured by aircraft at 975 millibars just before landfall and the same pressure was again measured when the eye moved back over water. Accelerating toward the Bahamas, there was further strengthening and Lili went through the central Bahamas early on the 19th with sustained winds of near 90 knots. The eye, 30 to 40 nautical miles wide, moved over Great Exuma and San Salvadore and the eye wall affected portions of Long Island, Rum Cay, and Cat Island.
Shortly thereafter, at 0000 UTC on the 20th and just east of the Bahamas, the hurricane reached its peak strength, with an estimated 100-knot maximum sustained wind and a central surface pressure of 960 mb. This is a category three on the Saffir/Simpson hurricane intensity scale and Lili is the sixth category three or higher hurricane in the Atlantic basin in 1996.
Lili continued moving northeastward, its center passing about 140 n mi southeast of Bermuda on the 20th. By now, the strongest winds were on the southeast side of the center and Bermuda's sustained winds did not reach tropical storm force. Lili's winds gradually decreased from the 100-knot maximum on the 20th to 65 knots on the 21st.
On the 22nd, having turned eastward, the forward motion decelerated to almost stationary as a mid-level short-wave high pressure ridge came into longitudinal phase with Lili. Lili drifted erratically eastward across the central north Atlantic until the 24th, when another acceleration toward the northeast began. Lili reintensified to 85 knots on the 25th and finally weakened to a tropical storm on the 26th, as the center was passing about 300 n mi northwest of the Azores. Lili is estimated to have become extratropical on the 27th. It remained a 55-knot extratropical storm until crossing over Great Britain on the 28th. Its remnants crossed the northern European mainland on the 29th.
Any satellite data used was based on the Dvorak satellite intensity estimating technique as applied at the Tropical Analysis and Forecast Branch (TAFB), the Satellite Aanalysis Branch (SAB), and the U.S. Air Force Global Weather Center (AFGWC).
Aircraft data is from eleven aircraft reconnaissance missions into Lili over a five-day period, from the 15th to the 20th, resulting in 37 center penetrations. Seven of the missions were performed by the U.S. Air Force Reserve Unit out of Keesler AFB, Mississippi. The other four missions were performed by the NOAA research aircraft when Lili's center was near Cuba. The maximum wind speed measured by aircraft was 112 knots at the 700 mb level, at 0855 UTC on the 19th in the southeast quadrant. The minimum surface pressure from the aircraft was 960 millibars at 1218 UTC on the 19th.
The highest sustained wind from Cuba was a 10-minute average of 80 knots reported from Cayo Largo del Sur, an island located about 50 nautical miles east of the Isle of Youth. The center was over mainland Cuba and about 40 nautical miles north of the island at the time of the report. An 80-knot 10-minute wind was also reported from San Salvador in the central Bahamas at the time that the center was located about 15 nautical miles to its north-northwest.
Two hours after the report from San Salvador, at 1200 UTC on the 19th, a ship with call sign ZCBC3 reported an estimated wind speed of 99 knots, while located about 20 nautical miles south of the center. The 112-knot aircraft wind was measured only a few hours earlier and the hurricane's estimated maximum sustained wind speed of 100 knots is based on these measurements.
There was heavy rainfall over portions of Cuba with over 26 inches accumulated at La Moza.
Sustained wind speeds to about 45 knots with gusts to as high as 78 knots (from Alderney, a channel island) were reported from Great Britain, when Lili was extratropical, on the 28th and 29th.
During the formative state of the tropical cyclone, heavy rain occurred over portions of Central America. The Associated Press reported five drowning deaths in Honduras and three deaths in Costa Rica. In addition, thousands were left homeless in both of these countries and there was flooding in Nicaragua as well.
In Cuba, there was extensive damage to agriculture and thousands were made homeless according to Reuters news. Reuters also reported that six were killed in Great Britain from Lili as an extratropical storm. Four died in traffic accidents and two fishermen were swept into the sea.
In the Bahamas, reports from Georgetown on Great Exuma island suggest that many houses were substantially damaged and many boats were sunk. A storm tide of 15 feet above mean sea level was estimated on the north side of Great Exuma.