Carlotta was a category 4 hurricane (on the Saffir-Simpson scale) that had a
long offshore track parallel to the coast of Mexico. Its maximum winds of
135 kt make Carlotta the second strongest June hurricane (to Ava in 1973) in
the east Pacific record since 1966. Although the hurricane did not make
landfall, it was responsible for 18 deaths when the Lithuanian freighter
M/V Linkuva was caught in the hurricane and was lost at sea.
a. Synoptic History
A tropical wave that emerged from the coast of Africa on June 3rd,
and crossed into the eastern Pacific basin on the 15th, appears to
have been the precursor disturbance of Hurricane Carlotta. Surface analyses
show a weak low beginning late on the 16th near 8N, 88W, and
Dvorak satellite classifications began around 1200 UTC on the 17th.
Convection was broadly distributed and disorganized, however, until about
1200 UTC on the 18th, when a concentration of deep convection
developed just south of the Gulf of Tehuantepec. Ship reports and satellite
scatterometer data suggest that the season's third tropical depression
formed from this system by 1800 UTC about 235 n mi southeast of Puerto
Angel, Mexico.
The best track chart of the tropical cyclone's path is given in
Figure 1, with
the wind and pressure history shown in Figure 2 and
Figure 3, respectively.
The complete best track is given in Table 1.
The depression strengthened as it moved to the west-northwest at about 11
kt, and became Tropical Storm Carlotta at 0000 UTC 19 June when the cyclone
was centered about 180 n mi south-southeast of Puerto Angel. As Carlotta
edged toward the coast, it came under the influence of a mid-tropospheric
ridge to its north and turned slightly to the left; its closest approach to
the Mexican coast was about
120 n mi near 1200 UTC on the 19th. Late on the 19th,
a ragged banding eye became visible on satellite imagery and this was
followed by the appearance of very deep convection around the developing eye.
Carlotta reached hurricane status at 0600 UTC on the 20th, when it
was about 135 n mi south of Acapulco. Once hurricane strength was attained,
the pace of intensification increased dramatically; 24 h later at 0600 UTC on
the 21st, Carlotta reached its peak intensity of 135 kt. Although
Carlotta exhibited impressive upper-level outflow over its southern
semicircle, outflow was limited to the north of the cyclone during most of
the intensification period.
Shortly after reaching peak intensity, Carlotta turned from a general
westerly heading to a west-northwest track at a reduced speed, about 7-8 kt,
around the western edge of the mid-tropospheric ridge over Mexico. By 0000
UTC on the 22nd, Carlotta had weakened to about 100 kt. On the
22nd the weakening trend was temporarily halted with some
oscillations in the convective intensity and eye definition. The weakening
trend resumed for good on the 23rd. Over the next two days,
Carlotta moved to the northwest between 10 and 14 kt over cooler waters,
falling below hurricane strength shortly after 0000 UTC on the
24th, when it was centered about 225 n mi west-southwest of Cabo
San Lucas. Convection continued to diminish and the system became a
tropical depression by 0000 UTC on the 25th. No further deep
convection was noted after 0600 UTC on the 25th, when the tropical
cyclone dissipated about 415 n mi west of Cabo San Lucas. A swirl of low
clouds persisted in this area for several days thereafter.
b. Meteorological Statistics
Observations in Hurricane Carlotta (Figure 2 and
Figure 3) include satellite Dvorak
technique intensity estimates from the Tropical Analysis and Forecast Branch
(TAFB), the Satellite Analysis Branch (SAB) and the U. S. Air Force Weather
Agency (AFWA). In addition, flight-level and dropwindsonde observations were
available from a flight of the 53rd Weather Reconnaissance
Squadron of the U. S. Air Force Reserve Command.
Of particular interest is a comparison of the aircraft and satellite-based
intensity estimates during the period of reconnaissance coverage from about
1900-2200 UTC on the 20th. It is clear that the satellite
intensity estimates were substantially in error, having overstated the
intensity of Carlotta during this period by about 20 mb and 15-20 kt. The
reconnaissance aircraft measured a minimum sea-level pressure of 977 mb at
1901 UTC, while the Dvorak estimate from TAFB and SAB (interpolated to the
time of the reconnaissance fix) was about 20 mb lower. Similarly, the
Dvorak-based maximum wind estimate at this time was about 105 kt, while the
aircraft found peak flight-level winds no higher than 96 kt (estimated
equivalent of 86 kt at the surface) during its first full "alpha" pattern.
A GPS dropwindsonde at 2040 UTC in the northwest eyewall, where the maximum
flight-level winds were found during the first alpha pattern, reported a
surface wind of 91 kt, about 17 kt less than the satellite estimate
(interpolated to the time of the drop).
The aircraft did find that Carlotta was deepening rapidly; from 1901 to 2142
UTC the minimum pressure fell by 7-8 mb to 970 mb, representing a deepening
rate of just less than 3 mb h-1. At 2146 UTC, the aircraft
reported a flight-level wind of 105 kt (estimated equivalent of 95 kt at the
surface). By this time, however, the satellite intensity estimates had also
increased, to 110 kt and about 952 mb.
The sizable discrepancy between the satellite and reconnaissance estimates
makes determining the maximum intensity of Carlotta problematic, as
satellite imagery indicates that Carlotta continued to strengthen rapidly
for another 9 hours or so after the conclusion of the reconnaissance
coverage. Conventional Dvorak estimates reached 140 kt (921 mb) at 0600 UTC
on the 21st, and the University of Wisconsin objective Dvorak
12-h weighted average estimate peaked at this time with a value of 146 kt
(915 mb). For purposes of determining the best track intensity, it is
assumed that the satellite high bias was present for about 24 hours before
and after the time of the reconnaissance flight. Using this approach, the
maximum intensity of Carlotta is estimated to have been 135 kt. The
estimated time of peak intensity (0600 UTC 21 June) is based on the sequence
of objective Dvorak numbers.
There is considerable uncertainty regarding the minimum pressure attained by
Carlotta. The Dvorak pressure-wind curve associates a pressure of 926 mb
with winds of 135 kt. However, a comparison of reconnaissance winds and
pressures suggests that the observed pressures in Carlotta were 5-10 mb
higher than those predicted by the Dvorak pressure-wind curve. Therefore,
the minimum pressure, which occurred shortly thereafter, is believed to be
somewhat higher than 926 mb. The final value of 932 mb at 0600 UTC on the
21st was obtained by assuming a deepening rate of 5 mb
h-1 subsequent to the best track estimate of 962 mb at
21/0000 UTC. This assumed deepening rate is close to the extreme short term
intensification rates observed in 1988's Hurricane Gilbert and 1995's
Hurricane Opal, and as a result, the assigned 932 mb minimum pressure for
Carlotta probably represents a lower bound on the true value.
Ship reports of winds of tropical storm force associated with Carlotta are
listed in Table 2.
No land stations reported sustained tropical storm force
winds. Bahias De Huatulco (MMBT) reported a gust to 38 kt at 1300 UTC on
June 19th.
c. Casualty and Damage Statistics
According to media reports, the Lithuanian freighter M/V Linkuva,
along with its crew of 18 persons, was lost when the ship was caught in the
hurricane
220 miles southwest of Acapulco late on June 20th after an engine
failure. The last contact with the M/V Linkuva occurred during the
period of rapid intensification and just before the Carlotta reached its peak
intensity. The vessel was en route to Long Beach, California.
There are no other reports of damage or casualties.
Forecast and Warning Critique
Average official track errors for Carlotta were 29, 59, 92, 110, and 124 n
mi for the 12, 24, 36, 48, and 72 h forecasts, respectively; these were
somewhat lower than the average official track errors for the 10-yr period
1990-1999 (Table 3).
However, the track errors for Carlotta were somewhat larger than the
guidance from the UK Met. Office global model (UKMI). The GFDL model had a
significant rightward bias with errors much larger than the official
forecast, presumably due to a poor vortex initialization in the Aviation
model. Although the official track forecast errors were smaller than the
long-term mean, Fig. 4 shows that the three modest changes in Carlotta's
track: the initial leftward turn near 96W, the turn to the northwest near
106W, and the final leftward turn near 114W, were not well
anticipated.
Figure 5 shows selected official intensity forecasts
plotted against the best track. The initial intensification to hurricane
strength was well forecast; however, the rapid strengthening to category 4
was not, even after the process was underway. The worst forecast errors
(all underestimates) for the 12, 24, 36, 48, and 72 h forecasts were 40, 45,
50, 60, and 50 kt, respectively. Neither the SHIPS nor GFDL guidance models
forecast the rapid strengthening to category 4. The decay stage was
reasonably-well forecast.
Table 4 lists the watches and warnings associated with
Carlotta issued by the government of Mexico. As noted above, no sustained
tropical storm force winds were observed over land.
Table 1.
Best track for Hurricane Carlotta, 18-25 June 2000.
Date/Time (UTC) | Position |
Pressure (mb) |
Wind Speed (kt) | Stage |
Lat. (°N) | Lon. (°W) |
18 / 1800 | 12.5 | 94.0 | 1003 | 30 | tropical depression |
19 / 0000 | 13.0 | 95.0 | 1002 | 35 | tropical storm |
19 / 0600 | 13.5 | 96.1 | 1000 | 45 | " |
19 / 1200 | 13.8 | 97.2 | 998 | 50 | " |
19 / 1800 | 14.1 | 98.3 | 995 | 55 | " |
20 / 0000 | 14.3 | 99.3 | 992 | 60 | " |
20 / 0600 | 14.5 | 100.2 | 989 | 65 | hurricane |
20 / 1200 | 14.7 | 101.2 | 985 | 75 | " |
20 / 1800 | 14.9 | 102.1 | 981 | 85 | " |
21 / 0000 | 15.1 | 103.1 | 962 | 110 | " |
21 / 0600 | 15.1 | 103.8 | 932 | 135 | " |
21 / 1200 | 15.3 | 104.5 | 934 | 135 | " |
21 / 1800 | 15.6 | 105.3 | 938 | 130 | " |
22 / 0000 | 15.9 | 106.0 | 949 | 115 | " |
22 / 0600 | 16.3 | 106.6 | 960 | 100 | " |
22 / 1200 | 16.8 | 107.2 | 960 | 100 | " |
22 / 1800 | 17.3 | 107.9 | 960 | 100 | " |
23 / 0000 | 17.9 | 108.7 | 960 | 100 | " |
23 / 0600 | 18.6 | 109.6 | 963 | 95 | " |
23 / 1200 | 19.4 | 110.5 | 970 | 85 | " |
23 / 1800 | 20.3 | 111.5 | 979 | 75 | " |
24 / 0000 | 21.2 | 112.7 | 987 | 65 | " |
24 / 0600 | 22.0 | 113.8 | 994 | 55 | tropical storm |
24 / 1200 | 22.6 | 114.8 | 999 | 45 | " |
24 / 1800 | 23.2 | 115.8 | 1002 | 35 | " |
25 / 0000 | 23.6 | 116.6 | 1004 | 30 | tropical depression |
25 / 0600 | 24.0 | 117.3 | 1006 | 25 | " |
|
21 / 0600 | 15.1 | 103.8 | 932 | 135 | minimum pressure |
Table 2.
Ship reports with winds of at least 34 kt for Hurricane Carlotta, 18-25 June 2000.
Date/ Time (UTC) |
Ship Call Sign |
Lat. (°N) |
Lon. (°W) |
Wind dir/speed (deg/kt) |
Pressure (mb) |
18/1800 | 4XGT | 13.2 | 93.8 | 070/35 | 1008.8 |
19/1800 | KAOU | 15.0 | 98.0 | 070/36 | 1010.0 |
19/2100 | KAOU | 15.0 | 98.0 | 090/40 | 1008.0 |
20/0000 | KAOU | 15.1 | 98.1 | 110/35 | 1009.1 |
20/1500 | OWZU2 | 16.8 | 100.8 | 100/35 | 1010.0 |
21/1500 | 4XFD | 18.1 | 103.4 | 090/40 | 1011.0 |
22/0000 | DGOS | 17.9 | 103.4 | 090/34 | 1011.0 |
23/0000 | JFUG | 19.8 | 106.0 | 120/39 | 1009.3 |
23/0600 | ELWZ5 | 20.7 | 106.8 | 140/35 | 1012.0 |
Table 3.
Preliminary forecast evaluation (heterogeneous sample) for
Hurricane Carlotta, 18-25 June 2000. Forecast errors for tropical storm and
hurricane stages (n mi) are followed by the number of forecasts in
parentheses. Errors smaller than the NHC official forecast are shown in
bold-face type.
Forecast Technique |
Period (hours) |
12 | 24 | 36 | 48 | 72 |
CLIP | 31 (22) | 64 (20) | 109 (18) | 148 (16) | 191 (12) |
GFDI | 43 (22) | 105 (20) | 196 (18) | 226 (14) | 325 (8) |
LBAR | 26 (22) | 60 (20) | 113 (18) | 176 (16) | 312 (12) |
AVNI | 46 (15) | 102 (15) | 168 (12) | 109 (3) | 147 (3) |
BAMD | 34 (22) | 57 (20) | 86 (18) | 125 (16) | 210 (12) |
BAMM | 30 (22) | 49 (20) | 86 (18) | 135 (16) | 262 (12) |
BAMS | 30 (22) | 45 (20) | 73 (18) | 117 (16) | 233 (12) |
NGPI | 42 (21) | 100 (19) | 95 (15) | 134 (13) | 201 (5) |
UKMI | 26 (20) | 44 (18) | 68 (16) | 93 (14) | 132 (10) |
GUNS | 29 (20) | 66 (18) | 72 (14) | 80 (12) | 89 (4) |
NHC Official | 29 (22) | 59 (20) | 92 (18) | 110 (16) | 124 (12) |
NHC Official (1990-99 mean) | 37 (2494) | 69 (2245) | 101 (1993) | 132 (1760) | 189 (1353) |
Table 4.
Watch and warning summary for Hurricane Carlotta, 18-25 June 2000.
Date/Time (UTC) |
Action |
Location |
18 / 2100 | Tropical Storm Warning issued | Salina Cruz to Acapulco |
19 / 0900 | Hurricane Watch issued | Puerto Angel to Zihuatanejo |
19 / 0900 | Tropical Storm Warning extended | Acapulco to Zihuatanejo |
19 / 1800 | Tropical Storm Warning discontinued | Salina Cruz to Puerto Angel |
20 / 0300 | Hurricane Watch discontinued | Puerto Angel to Acapulco |
20 / 0900 | Hurricane Watch discontinued | Acapulco to Zihuatanejo |
20 / 1200 | Tropical Storm Warning discontinued | Puerto Angel to Acapulco |
20 / 1500 | Tropical Storm Warning discontinued | Acapulco to Zihuatanejo |
23 / 0900 | Tropical Storm Watch issued | Baja California south of Cabo San Lazaro |
23 / 2100 | Tropical Storm Watch discontinued | Baja California south of Cabo San Lazaro |
Figure 1.
Best track positions for Hurricane Carlotta, 18-25 June 2000.
Figure 2.
Best track maximum sustained surface wind speed curve for Hurricane
Carlotta, 18-25 June 2000, and the observations on which the best track
curve is based. Aircraft observations have been adjusted for elevation
using 90%, 80%, and 85% reduction factors for observations from 700 mb, 850
mb, and 1500 ft, respectively. Dropwindsonde observations include actual 10
m winds (sfc), as well as surface estimates derived from the sounding
boundary layer mean (MBL). Objective Dvorak estimates are 12-h averages,
weighted most heavily by the most recent values.
Figure 3.
Best track minimum central pressure curve for Hurricane Carlotta, 18-25 June
2000, and the observations on which the best track curve is based.
Objective Dvorak estimates are 12-h averages, weighted most heavily by the
most recent values.
Figure 4.
Selected official track forecasts (dashed lines, with 0, 12, 24, 36, 48, and
72 h positions indicated) for Hurricane Carlotta, 18-25 June 2000. The best
track is given by the thick solid line with positions given at 6 h
intervals.
Figure 4.
Selected official intensity forecasts (dashed lines) for Hurricane Carlotta,
18-25 June 2000. The best track intensity is given by the thick solid line.