Analysis of the heat index in the Mesoamerica and Caribbean region

Hourly data collected from ground stations were used to study the maximum daytime heat index Hi in the Mesoamerica and Caribbean Sea (MAC) region for a 35-yr period (1980-2014). Observations of Hi revealed larger values during the rainy season and smaller values during the dry season. The Hi climatology exhibits the largest values in Mesoamerica, followed by the Greater Antilles and then by the Lesser Antilles. The trend in Hi indicates a notable increasing pattern of 0.05°C yr-1 (0.10°F yr-1), and the trends are more prominent in Mesoamerica than in Caribbean countries. This work also includes the analysis of heat index extreme events (HIEE). Usually the extreme values of the heat index are used for advising heat warning events, and it was found that 45 HIEEs occurred during the studied period. The average duration of HIEE was 2.4 days, and the average relative intensity (excess over the threshold) was 2.4°C (4.3°F). It was found that 82% of HIEE lasted 2 or 2.5 days and 80% exhibited relative intensity of 3°C (5.4°F) or less. It was also found that the frequency of extreme events has intensified since 1991, with the highest incidences occurring in 1995, 1998, 2005 and 2010, and these years coincide with the cool phase of El Niño-Southern Oscillation (ENSO). Therefore, the occurrences of HIEE in the MAC region appear to be at least partially influenced by ENSO episodes.