a. Synoptic History
Luis was a category 4 Cape Verde hurricane
that wreaked harm and havoc on the northeasternmost of the Leeward Islands, with an
estimated sixteen dead and two-and-a-half billion dollars in damages.
Luis was first detected as a tropical wave
and circulation of low clouds on 26 August over the far eastern tropical Atlantic
between the coast of Africa and the Cape Verde Islands. The low-
level cloud circulation moved westward and is estimated to have
developed a weak surface circulation on the 27th near the Cape
Verde Islands. The official track of Luis, listed in Table 1
and plotted in Fig. 1 (94K GIF),
begins at this time.
While Luis was developing, there were three other
tropical cyclones in the Atlantic,
to the west and northwest...Humberto,
Iris and Karen.
Luis strengthened from a depression to a storm on
the 29th, but its deep convection fluctuated for the next two days
while there was strong vertical shear nearby. The shear diminished
on the 30th; an eye
formed and Luis quickly became a hurricane. The intensification process
continued for the next two days as Luis moved west-northwestward. A reconnaissance
aircraft reached the hurricane late on the 3rd of September and confirmed the
satellite intensity estimates of a
category 4 hurricane on the Saffir/Simpson scale.
Luis was located about 600 n mi east of the Lesser Antilles at this time.
The track heading turned from westward to northwestward on the
5th and the hurricane moved across the northeastern Leeward
Islands. The center
passed directly over Barbuda and close enough
to the northeast of Antigua, St. Barthelemy, St. Martin and Anguilla
that the southern portion of the eyewall
affected these islands. Luis' sustained winds in the eyewall were as high as
115 knots at this time, just below 120-knot
maximum values which had occurred for the previous 48 hours.
Luis was a large hurricane. The inner diameter of the eyewall
was 40 n mi as it moved over the islands. In addition to the
eyewall conditions described above, Nevis, St. Kitts, St. Eustatius
and the northernmost British Virgin Islands experienced hurricane-force
wind speeds, while tropical storm conditions affected the
remainder of the British and U.S. Virgin Islands and the eastern
islands of Puerto Rico.
Luis gradually recurved across the north Atlantic. The center
of the hurricane passed about 200 miles west of Bermuda on the 9th
of September, causing tropical storm force winds there. Luis
on the 11th, as it moved over eastern Newfoundland, where high winds and sea
conditions were also reported.
b. Meteorological Statistics
The minimum sea-level pressure and flight-level wind speed
observations from reconnaissance aircraft are plotted in
Figs. 2 and 3 (63K GIF) respectively.
Wind speed estimates from satellite data are
plotted in Fig. 3 and the
corresponding pressure from the Dvorak pressure-wind relation is plotted in
Fig. 2. A small selection of
surface observations are also plotted. Table 2 lists some
significant surface observations and Table 3
lists ship reports of tropical storm conditions.
The highest reconnaissance wind speed was 146 knots
at 1306 UTC on the 4th at a flight level of 700 mb. A surface pressure of
945 mb was measured at this time. The surface pressure did not
reach its minimum value of 935 mb until late on the 7th, at which
time aircraft winds were near 120 knots. The ship TEAL ARROW was
in the center of the hurricane at 1800 UTC on the 6th and measured
a sea-level pressure of 942 mb. The ship reported sustained winds
of 64 knots at 1500 UTC and measured
99 knots at 2100 UTC and again at 0300 UTC
on the 7th. The highest ship gusts were 125 knots and
wave heights to 50 feet were estimated.
The official highest sustained surface wind attained by Luis is
estimated to be 120 knots from the 3rd through the 5th while it was
approaching the Leeward Islands. This speed is 82 percent of the
highest aircraft wind speed of 146 knots. Sustained wind speeds
were still at 115 knots as Luis moved over the islands.
Table 2 shows that sustained hurricane-force
winds were reported from Antigua, Guadeloupe, St. Barthelemy and St. Maartin.
The observations of sustained near-surface wind speeds of 105 and
108 knots at Antigua and St. Barthelelmy imply that even higher
values may have occurred nearby. Since the eye of the hurricane
went over Barbuda, it is expected that sustained winds of near 115
knots were experienced there. The winds at Auguilla were likely in
the 105- to 115-knot range.
Later and further north, Bermuda reported a maximum sustained
wind of 40 knots as the center passed some 200 n mi to the west.
The QUEEN ELIZABETH 2 encountered a rogue wave of 95 feet
early on the 11th while located 200 n mi south of eastern
Newfoundland and 120 n mi southeast of the center of the tropical
cyclone, which is estimated to have had 80-knot sustained
winds at that time. A nearby Canadian data buoy reported a peak wave height
of 98 feet at about the same time.
On the afternoon of the 8th, ten drifting data buoys were
deployed by the
U.S. Air Force Reserve 53rd Weather Reconnaissance Squadron
some 300 n mi ahead of Luis, along 31 degrees north latitude and
from 71 to 66 degrees west longitude. Sustained winds of 72 knots
with gusts to 95 knots were measured as the hurricane passed,
but this observation was not at the location of strongest
winds as indicated by aircraft reconnaissance data. The buoys also
measured pressure and air and sea temperature and there was a 3.5
C decrease in sea surface temperature to the east of the center
after Luis went by.
c. Casualty and Damage Statistics
The hurricane killed an estimated 17 persons and caused
extensive damage when it moved across the northeastern edge of the
Leeward Islands of the Caribbean. Nine died in St. Martin, three
in Antigua and Barbuda, two in Puerto Rico, one in Guadeloupe, and
one in Dominica. Days later, there was one storm-related death in
Dollar damage totals are unknown. At Barbuda, where a full
Category 4 hurricane was experienced, the damage to structures was
estimated at 70 percent along with severe flooding and erosion.
The estimate for St. Maartin and St. Martin is 60 percent damage.
The prime minister of Antigua was quoted as saying that nearly half
the homes on that island were destroyed. A damage estimate for St.
Maartin, alone, is 1.8 billion dollars. With great uncertainty,
the total damage estimate for Hurricane Luis is temporarily set at
2.5 billion U.S. dollars.
d. Forecast and Warning Critique
Official track forecast errors were quite small for Hurricane
Luis ranging from 52 n mi at 24 hours to 173 n mi at 72 hours.
This compares to the previous ten-year average of 98 n mi at 24
hours and 296 n mi at 72 hours.
Luis became and remained a Category 4 hurricane several days
before hitting the islands. This persistence provided local
officials with ample time to prepare for an intense hurricane.
Table 4 lists the sequence of the various watches and
warnings issued. A hurricane watch
was issued for Antigua and nearby islands at 0900 UTC on the 3rd and a
hurricane warning was issued
at 0000 UTC on the 4th. Tropical storm force winds began at
Antigua at 0500 UTC on the 5th, so that there was a lead time of 29
hours between the time that the warning was issued and the onset of
gales. Lead times for the other islands were similar.
Hurricane warnings were issued at 0000 UTC, as stated on
advisory no. 26, from Antigua to St. Martin. The wording implies
that St. Barthelemy and St. Martin were included; in fact, these
islands were not put under a hurricane warning until 1500 UTC by
French officials as stated on advisory no. 29.