Hurricane Iris was a small but severe Category Four hurricane that devastated southern Belize.
a. Synoptic History
The precursor of Iris was a poorly defined tropical wave that moved westward across the tropical Atlantic during the last days of September. A very hostile upper-level wind environment, caused by a large upper-level trough with an embedded low centered just to the northeast of the Lesser Antilles, prevailed over the Atlantic. As the tropical wave reached 50 W on the 3rd of October, the upper-low became detached from the trough and began to move toward the southwest over the eastern Caribbean Sea. This resulted in the development of an upper-level ridge over the tropical wave providing a more favorable environment for tropical cyclone formation. While this pattern was evolving, satellite imagery indicated an increase in the thunderstorm activity and a cyclonic rotation in the mid-levels. Gradually, a low-level cloud circulation became more pronounced on satellite imagery and was later confirmed by surface observations. It is estimated that a tropical depression with a poorly-defined center formed from this system about 85 nautical miles southeast of Barbados at 1200 UTC 4 October.
The depression moved toward the west and west-northwest through the southern Windward Islands, accompanied by squalls and significant (> 3 mb) 24-h pressure falls. It is estimated that the depression reached tropical storm status at 1200 UTC 5 October, about 240 nautical miles south-southeast of San Juan Puerto Rico. Although the cloud pattern continued to be impressive on satellite and was typical of a tropical storm, the low-level center was very poorly defined as indicated by several passes of a reconnaissance plane through the system. Only a gradual strengthening occurred during the following 12 to 18 hours and Iris became a hurricane very near the Barahona Peninsula, Dominican Republic at 1800 UTC 6 October.
The well-established middle-level ridge north of Iris became stronger and forced the tropical cyclone to move on a straight westward track. This allowed Jamaica to escape from the small core of Iris which passed just to its south during the morning of the 7th. Once Iris moved away from Jamaica and headed for Belize, it moved over a region where the upper-oceanic heat content was very high. As a result of favorable atmospheric and oceanic conditions, intensification began and the minimum pressure dropped from 990 mb to 950 mb in about 18 hours and the winds increased from 86 to 138 mph. Iris became a powerful Category Four hurricane on the Saffir/Simpson Hurricane Scale (SSHS) by 1200 UTC 8 October. Historically, a large number of hurricanes have become major hurricanes in this portion of the Caribbean Sea.
Near the time of the peak intensity, the hurricane hunter plane reported three small concentric eyewalls and an hour later the inner eyewall collapsed . The maximum winds then temporarily decreased to 132 mph. The hurricane moved on a track between the west and west-southwest and based on radar from Belize, Iris made landfall in southern Belize in the vicinity of Monkey River Town around 0200 UTC 9 October. This location is about 60 nautical miles south of Belize City. Iris intensified just before landfall and the maximum winds peaked at 144 mph with a minimum pressure of 948 mb. Thereafter, Iris continued westward and weakened rapidly over the mountains of Central America. The low-level center could no longer be traced by 1800 UTC 9 October.
b. Meteorological Statistics
Iris was characterized by the small diameter of its core. The first reconnaissance into the system had difficulties in closing the circulation, not only because it was poorly defined but also because the center of circulation was very small. Furthermore, despite the good organization of the cloud pattern on satellite, the surface center was so small and poorly defined that the reconnaissance plane had to climb to 850 mb to" fix" it on the 5th about 1800 UTC. Extrapolated minimum pressure at that time was 1004 mb with flight-level winds to near 74 mph. A post-analysis of pressure, wind and Dvorak classifications suggests Iris reached tropical storm status earlier than indicated in the advisories. Iris was upgraded to a hurricane at 1800 UTC 6 October, based on reports from a reconnaissance plane of a 1500-foot flight level peak wind of 94 mph and the presence of a closed eyewall near that time. A couple of hours later a GPS dropsonde launched from an Air Force plane indicated that surface winds peaked at 86 mph. Iris was upgraded to Category Four Hurricane with 138 mph at 1200 UTC 8 October based on a 154-mph wind reduced from 700-mb. Because the eye was so small, dropsondes never hit the true center. The 954 mb reported by the drop was then adjusted to 950 mb. After an eyewall replacement cycle and a temporary weakening, Iris re-intensified and the winds peaked at 144 mph with a minimum pressure of 948 mb. This is based on a 146-mph surface winds measured by a dropsonde combined with satellite objective T-numbers between 6.5 and 7.0 on the Dvorak scale for about 3 hours. The maximum winds recorded at Belize was a gust of 122 mph on Carmen Davis station in Big Creek at 16.5 N 88.4 W at 0200 UTC 9 October.
c. Casualty and Damage Statistics
There were 31 deaths attributed to Iris; 28 in Belize and
3 in Dominican Republic.
Maximum Intensity For Hurricane Iris
for Hurricane Iris