Hurricane Marco drifted aimlessly over the western Caribbean Sea
for about a week threatening several land areas but never making landfall.
a. Synoptic History
A cold front moved into the northwestern Caribbean on 9
November, followed by an abnormally strong high pressure system
which dominated the eastern United States. The front became
nearly stationary and interacted with a series of westward moving
tropical waves.
The Intertropical Convergence Zone (ITCZ) became active
in the southwestern Caribbean as monsoonal southwesterly
flow from the eastern Pacific reached the area. As early as 13
November, surface analysis showed a weak low pressure area just
north of Colombia and, by the next day, there was a well-defined
but broad low-level circulation between Jamaica and Honduras. At
that time, the system did not meet the criteria for
tropical depression
status because the convection was not concentrated nor
organized near a center
of circulation. In fact, there were
several smaller centers of circulation embedded within a much
larger system. The broad area of low pressure drifted northward
for a couple of days, and in combination with a high pressure
system over the United States, produced
gale force
winds over Florida, Cuba, the Bahamas and the Gulf of Mexico.
The convection gradually became organized south of Jamaica
and a post-analysis of the surface and
reconnaissance aircraft
data indicates that the system became a tropical depression at
1800 UTC November 16. The poorly-defined tropical depression
moved generally southward and encountered a much better upper-level
environment for strengthening. It became a
tropical storm
at 0600 UTC 19 November and then moved on a slow east-northeast
track. Marco briefly reached hurricane
status at 0600 UTC 20 November with maximum winds of 65 knots
and a minimum pressure of 983 mb. Thereafter, Marco was hit by strong upper-level
westerlies and weakened rapidly to a tropical depression at 1800
UTC 23 November. It was then located just to the southeast of Jamaica.
Once a middle-level ridge rebuilt over the Bahamas and Florida,
Marco turned toward the west and west-northwest and regained
tropical storm strength. The tropical cyclone
was south of the western tip of Cuba when it interacted with a cold front and
dissipated by 1800 UTC 26 November. The remnants of Marco drifted
southward and produced heavy rains over Honduras and Belize.
Marco was characterized by its numerous intensity
fluctuations. For several consecutive days, Marco became
disorganized during the afternoon when the low-level center was
practically exposed and there was an increase in the central
pressure. This was followed by a significant redevelopment of the
convection and a drop in pressure during the nights and early
mornings. These fluctuations could be attributed to the
interaction of Marco with a series of fast moving shortwave
troughs and ridges observed on water vapor imagery. These
features increased and relaxed the shear while moving through the
area.
Marco's track is shown in
Fig. 1 (37K GIF).
Table 1 is a listing, at six-hour intervals, of the
"best-track" position,
estimated minimum central pressure and maximum 1-minute surface wind speed.
b. Meteorological Statistics
The best track pressure and wind curves as a function of time are shown in
Figures 2 (23K GIF)
and 3 (20K GIF)
and are based on reconnaissance and surface observations,
satellite intensity estimates from the
Tropical Analysis and Forecast Branch
(TAFB) of the Tropical Prediction Center. It also includes estimates from the
Synoptic Analysis Branch (SAB) and the
Air Force Global Weather Center
(AFGWC).
Marco was upgraded to a hurricane based on a 63-knot
1-min sustained wind reported by a U.S. Navy ship. Shortly thereafter.
A
reconnaissance plane
reported a minimum pressure of 983 mb and 1-sec wind of
89 knots. This was a significant pressure drop of
11 mb in 1 h and 40 minutes. During that flight, the crew
reported a volatile center structure with severe turbulence,
extreme rainfall and hail. Satellite images showed very cold
convective tops at that time. During the early morning flight of
22 November, the
reconnaissance plane
observed another pressure drop from 996 to 985 mb in about 2 hours, and a 5 n mi
diameter eye. The vessel PFAS reported sustained winds of 56 knots
and a pressure of 1007.5 mb at 1200 UTC 25 November. This observation
was used to operationally upgrade Marco to a tropical storm for
the second time.
Table 2 contains selected surface
observations and ships reporting 34-knot winds or higher.
c. Casualty and Damage Statistics
Marco never hit land but its large circulation brought heavy
rains to Central America and Hispaniola. These rains produced
floods and mud slides causing at least eight deaths. The
interaction of Marco during its developing stage with a strong
high over the U.S. resulted in gale force winds which produced
beach erosion along the east coast of Florida.
d. Forecast and Warning Critique
Since Marco moved very slowly watches or warnings were
in place for Jamaica for several days. Table 3
summarizes the watches and warnings associated with Marco. For about eight
consecutive days before Marco developed, the MRF consistently forecast the
formation of a tropical cyclone in the western Caribbean, (see
Fig. 4 [48K GIF]). This formation was also
suggested by both the
UKMET
and the ECMWF global models a couple of days later.
The official forecast errors ranged from 44 n mi at 12 hours
to 274 n mi at 72 hours. The 10-year average errors are 50 and
296 n mi respectively. The lowest errors at 72 hours (better
than the official) were produced by the UKMI, BAMS and BAMM and
the largest error was produced by VBRI. The GFDI (an interpolated
version of the GFDL model)
error was 349 n mi at 72 hours. Because Marco was a shallow tropical cyclone
for a long period, it was steered by the middle-to low-level tropospheric flow.
This probably contributed to such a low track 72-hour errors
produced by the BAMM and BAMS models.
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