RESUME OF THE 1998-1999 WINTER SEASON IN CUBA

Brief description of frontal systems that reached Cuba

The first cold front in the season arrived to the West of Cuba on October the 23^rd, as a moderate one, coinciding with the development of tropical storm Mitch East-Southeast of the island of San Andrés, Colombia, which later became the devastating hurricane of the West Caribbean. As this front passed over the western and Central Provinces, Mitch kept the high cloudiness of its outflow over Cuba, so the frontal band was partly masked by the cover of cirri and cirrostrati. This front didn’t produce any remarkable decrease in temperatures and its most relevant feature was the associated rainfall. On the 23^rd abundant rainfall was registered in the western part, mostly in the north coast, where they were locally intense. The Casablanca meteorological station registered 142.3 mm/24h, the greatest amount of rainfall at this station due to a frontal system on this century, and one of the greatest of all, including those produced by hurricanes. As the system moved east, heavy rains were registered over the province of Camagüey, standing out the values of 174,5mm fallen at La Gloria, 143,8 at Solas and 107,5 at Imías, all in the zone of Sierra Cubitas. Besides at Lombillo, Esmeralda 110,0 mm fell. All of these accumulates constitute 24 hours records for the month at those localities.

Only one front affected the country in November corresponding to the second of the season. It arrived to the West of the Country ranked as weak and crossed fast the entire island. The system was preceded by a wide band of clouds with showers and thunderstorms. It affected during the 4^th the western part and was related at first with the trough associated to tropical storm Mitch, which after loosing its tropical condition and integrating to the frontal system, acquired the characteristics of a squall line. Rainfall was heavy in Pinar del Río with significant accumulates of 111,4 mm/24h at San Juan y Martínez, 106,3 mm/24h at La Palma and 104.1 mm/24h at Santa Lucía.

Two cold fronts arrived to the West of Cuba in December, on the 14^th and the 30^th, both weak. The first one corresponding to the 3^rd of the season passed over all the provinces of the country and produced very low temperatures on inland zones of the west part during the early hours of days 17^th and 18^th. Remarkable minimum temperatures were reported at Bainoa station of 8,7 °C on the 17^th and 8,3 at Indio Hatuey on the 18^th. Other values of interest were reported on the 17^th at Indio Hatuey and Unión de Reyes with 9,2°C and Tapaste with 10,0°C. On the 18^th the thermometer descended to 9,3°C at Jovellanos and to 10,0°C at Bainoa. On the other hand, the fourth front affected only the north of the western provinces as a weak one with a slight decrease of maximum temperatures on days 30^th and 31^st, oscillating between 24°C and 25°C.

Three cold fronts arrived in January, with associated squall line activity. The first two, corresponding to fronts 5 and 6 of the season ran across the whole territory. Maximum temperatures of 21-24°C in the western and central regions turned out of interest with the lowest value at Tapaste of 21°C. Cold front number 7 caused very low minimum temperatures, as 12,2°C at Isabel Rubio, 13.2°C at Güira De Melena, 13,8ºC at Melena del Sur and Unión de Reyes, and 13,9ºC at Jagüey Grande.

Once more three fronts affected us in February. Cold front number 8, the first this month, arrived to the Cuban archipelago on day 13^th. It was ranked as moderate and covered the whole country, the same as number 10, that affected the territory since day 21^st. Cold front number 9 arrived to the west part of the country on day 19^th. Fronts 8 and 9 produced very low temperatures between 9 and 13°C while remarkable low temperatures were registered after front number 10. This time the coldest daybreak was on day 23^rd with the lowest reports from Indio Hatuey and Jagüey Grande with 7,0º C, Unión de Reyes with 7,2º C, Bainoa, with 8,0º C, Jovellanos with 8,º C, Melena del Sur with 8,5º C, Aguada de Pasajeros with 8,6º C, Colón with 8,º C and Tapaste with 9,0º C. Maximum temperatures also descended and on the 22^nd they were between 21°C and 25°C. With regard to rainfall, front number 9 was preceded by squall line activity with showers and thunderstorms that affected on the afternoon of the 18^th from Pinar del Río to Matanzas. Heavy rainfall was also reported at the station of San Juan y Martínez with 114mm/24h.

Also in March three fronts arrived to the National territory, the first of them on day 4^th, had a poorly defined cloud field, though it was preceded by an intense line of convective clouds over the Northeast of the Gulf of Mexico, which intensified and expanded southward since day 3^rd. The squall line started affecting the western region at about noon with abundant rainfall on the west and center of the country, including the Island of Youth. Also thunderstorms, strong winds and hailstorms occurred at some locations, as Santiago de Las Vegas. Though there was no remarkable rainfall, winds reached gusts of 99 km/h at Bahía Honda, 85 km/h at Casablanca, 96 km/h at Varadero, 86 km/h at Playa Girón, 77 km/h at Jovellanos, and 133 km/h at Sancti Spíritus. With the arrival of the squall line, temperature suffered an abrupt descent of 9,4 °C at Casablanca. At daybreak on March the 5^th the anticyclonic system had a value of 1024 hPa over the Carolines and its influence gave as result the coldest minimum temperatures of the season on the Havana – Matanzas plane with values of 6,9ºC at Bainoa, 8,6ºC at Tapaste, 9,0ºC at Unión de Reyes, 9,3ºC at Guira de Melena, 9,4ºC at Bauta and 10,0ºC at Batabanó. Casablanca reported a minimum of 14,8ºC, also the lowest temperature of the season. These values are, nevertheless far from the historical records of the month.

The twelfth front, the second of March affected the West region on the 14^th. The must significant features of this system were the strong swell and coastal floods at low zones of the North coast, including the Havana mole on the 15^th. This was due to the persistence of strong North winds for 12 to 18 hours, which originated wave trains over the Gulf of Mexico that reached these zones of the North coast of the West of Cuba.

The third front of March, the 13^th of the season affected very briefly on the 22^nd during the first hours of the morning the Northeast coast of the province of Pinar del Río and the North coast of Havana with some showers and rain. This front moved east dissipating quickly and produced no change in the maximum temperatures, but during the early hours of the 23^rd very cold temperatures were registered with the lowest report at Bainoa of 9,7ºC.

After 25 days without the arrival of any cold front to Cuba, front number 14 reached the West end of Cuba on April the 17^th, on the evening of the 18^th it arrived to Camaguey, where it stationed with some tendency to move back. On the 19^th it caused isolated rainfall, but on the 20^th the remains of the baroclinic zone over the north coast of the central region produced heavy rains during the early hours on the provinces of Villa Clara and Sancti Spiritus. The following amounts of interest in 24 hours: Caibarien 240 mm, Yaguajay 183 mm, Perea 76 mm, Mayajigua 66.5 mm, Iguará 57 mm and El Río 51 mm were reported.

It is an interesting point that the month of April was very warm. Remarkably high maximum temperatures were registered and records for the month were broken at several locations of the country. On day 11^th at Matanzas, the record for the month of April was broken with 37,4°C at Unión de Reyes. At Jagüey Grande 36,5ºC was registered, monthly record for the station, as well as 36,1ºC at Colón. On the 12^th the following values were reported: Aguada de Pasajeros 37,6ºC, Tapaste and Bainoa 35,6º C and 34, 9º C at Melena del Sur, new records for those stations on the month of April.

On the 17^th, in contrast with the winter like conditions prevailing over the west part of the country, several records of maximum temperature were registered on the eastern part. Amongst them was the absolute record for that variable on the country, reported at Jucarito, province of Granma, where the thermometer read 38.8°C. The former record was of 38.6 and dated from August 1969 at Guantánamo. This value was again reached at Jucarito on May the 27^th 1998. Absolute records were also broken for other locations like Las Tunas with 38.5 and Palo Seco, Holguín with 38.0 º C.

Cold front number 15, the last of the season arrived to the west of the country on May the 1^st. It was little active at first, but it intensified as it moved East and on day 2^nd it produced abundant rainfall on the eastern region, specially at the province of Holguín, where 107 mm were reported at Cueto, 85.2 mm at Sabanilla, and 78 mm at Barajagua. All of these are 24 hours registers.

This season was also a little active one with regard to the occurrence of south winds over the western part of the country, since only two such events took place. These winds, called "Sures" by Rodríguez and Ballester (1985), are due mainly to the influence of extratropical cyclones moving through the Gulf of Mexico or nearby states of the US.

According to the climatology of the "Sures" by Ballester, (1997) dating from the 1918-1919 season, this is the tenth season on which only two "Sures" affect the west of the country, while there are six where only one occurred. The last season with less "Sures" was that of 1991-1992.

On Table 3 the behavior of the "Sures" in the just ended season is presented as well as the historical values for the period 1918-1998. It can be seen that the current season showed well below the historical mean of 5,4. The first of the "Sures" occurred on March the 14^th associated to front number 12 and the second on April the 15^th. Both were ranked as moderate.

Table 3. Mean monthly frequency of "Sures" and behavior of the 1998-1999 season.

Temp.	Sep.	Oct.	Nov.	Dec.	Jan.	Feb.	Mar.	Apr.	May.	Total
1918-1919 1997-1998	0.04	0.05	0.08	0.27	0.65	1.22	1.72	1.04	0.32	5.4
1998-1999	0	0	0	0	0	0	1	1	0	2

Conclusions