Taking as base the chronology carried out by Rodríguez et. al (1984) and its later update in the Department of Weather Forecast of the Institute of Meteorology, charts 1 and 2 were built.

Chart 1. Dates of entrance and classification of the cold fronts that affected Cuba during the winter season of 1999-2000.

Number	Date of arrival	Classification
1	October 22nd 1999	Weak
2	October 24th 1999	Weak
3	November 2nd 1999	Weak
4	November 3rd 1999	Weak
5	November 27th 1997	Weak
6	November 30th 1999	Moderate (TC)
7	December 24th 1999	Weak (TC)
8	January 5th 2000	Weak
9	January 14th 2000	Moderate
10	January 21st 2000	Weak
11	January 24th 2000	Weak
12	January 26th 2000	Weak
13	February 5th 2000	Weak
14	February 8th 2000	Weak
15	April 5th 2000	Weak
16	April 9th 2000	Weak

Note: (TC) means that the cold front traveled all Cuba.

When analyzing and comparing the data presented in the Chart 1 with the historical ones the following issues are observed:

During the winter season of 1999-2000 16 cold fronts arrived to the national territory, quantity that allows to classify it as not very active, keeping in mind that the average for many years is 19,8 with a standard deviation ± 4.9.

When reviewing the 84 seasons lapsed from 1916-1917 until that of 1999-2000, it was found that the current season is the ninth in which Cuba is affected by 16 frontal systems, the last occasion happened in 1980-1981. That time also the last cold front arrived to the national territory in the month of April. The figure of 16 fronts is far from the absolute records of bigger and smaller quantity of fronts during a season, which belong to those of 1976-1977 with 35 and to that of 1996-1997, with only 11 cold fronts respectively.

Of the cold fronts that arrived to the Cuban archipelago during the season that is analyzed, 14 (87,5% of the total) were classified as weak and the 2 remaining (12,5% of the total) were moderate. No strong cold front affected the country, constituting the fourth winter season in a row in which this type of front does not affect the national territory. Historically 48% of the front systems that arrive in Cuba are classified as moderate, 42% as weak and 10% as strong.

Cold fronts, when moving to the East on the national territory suffer some weakening and to the oriental end as average, only half of those that affect the occident arrive. In this occasion five were the systems that traveled the whole country, value that represents 31% of the total, these systems shown in Chart 1 with the numbers 1,6,7,9 and 10.

Chart 2. Amount of cold fronts that have affected Cuba in the different months, from the season of 1916-1917 until that of 1998-1999 and behavior during the last two seasons.

Sea.	Sep.	Oct.	Nov.	Dec.	Jan.	Feb.	Mar.	Apr.	May.	Jun.	Total
1916 - 1999	7	110	212	270	296	280	247	162	60	4	1648
Ave	0,08	1,33	2,55	3,25	3,57	3,37	2,98	1,95	0,72	0,05	--
1998 - 1999	0	1	1	2	3	3	3	1	1	0	15
1999 - 2000	>0	2	4	1	5	2	0	2	0	0	16

On Chart 2 other data related with the Climatology of the cold fronts in Cuba are presented. When analyzing them the following characteristics arise:

The winter season of 1999-2000 had a normal beginning, as for the affectation of front systems to the national territory; although the arrival of two fronts in October is something above the average, in November that tendency continued with the arrival of four cold fronts, but in the last month of the year it was broken as only one front arrived, standing quite below the historical average. Just the opposite happened in January, since it was very active with the affectation to the country of five front systems, February finished with two fronts, somewhat below the average. March behaved in a peculiar way, since the national territory was not affected by any cold front, when revising the chronology of these systems it turns out that this it is the fifth time in 84 seasons that no front systems arrive in that month. The rest of the months were next to normal.

The first of the cold fronts of the current season arrived to the western end of Cuba in the afternoon of October the 22nd and it was preceded by an anticyclonic spillover; although it didn't cause a significant descent of the minimum temperatures, it did produce some freshening, more noticeable in the maximum temperatures. At the end of the dawn of the 24 the slight winter conditions were reinforced in the western half of the country with the arrival of the second front system. As a consequence of this reinforcement, in the dawn of the 25 a new minimum temperature record was settled for the month of October at the meteorological stations of Tapaste, Bauta and La Sabana, all in the province of Havana, with 12,6 °C in the first one and 14,0 °C in the two others.

From the 24 to the 28, and in association with the dissipation of these front systems, precipitation occurred with accumulates superior to 100 mm/24h in several towns of the provinces of Holguín and Guantánamo, standing out the one registered in Cayo Güin, province of Guantánamo, with 222,0 mm/24h the 28 (BVC a, 1999).

Of November 2nd the third cold front arrived to the western end. It traveled the whole country, but after reaching the oriental region it retrograded and remained along the north coast. In association with this meteorological situation intense rain was registered in the Havana provinces the day 11 with an accumulated in 24 hours of 321,0 mm at Calabazar, City of the Havana. The second front of the month arrived as a secondary front the day 3, after its pass strong winds of the northeast were onset for eleven days in a row.

The last front of the month, sixth of the season arrived to Cuba the day 30, after being structured in the Florida Strait. It was the first moderate cold front and it registered maximum sustained winds of 42 km/h and a maximum gust of 74 km/h in the meteorological station of Casablanca, City of Havana.

Only one front cold affected the Cuban archipi1élago in the month of December. It arrived to the occident the day 24. It was weak and traveled the whole country. Nevertheless, it was the coldest December in the last 20 years and the driest since 1941, (BVC b, 1999).

January was the most active month in the season, it overcame the average for many years, with the affectation of five front systems. The first one arrived to the western end the day 5, it was preceded by a band of prefrontal cloudiness that produced some rainfall during the previous afternoon in the western provinces, with the greatest accumulates of 32 mm/24h at Bahía Honda, Pinar del Río. This front arrived to the Havana provinces in state of dissipation.

On January 14 the ninth front of the season entered to the western end of Pinar del Río, the second of moderate kind, it produced sustained winds of 40 km/h and a maximum gust of 78 km/h in Casablanca, City of Havana. The day 21 Cuba was affected by the third front of the month and the 24th by the fourth, preceded by a line of storms that caused abundant precipitation, with accumulates of more than 100 mm/24h at several towns.

Winter conditions were reinforced on the 26th with the arrival of another front system and in the afternoon of the 27th the maximum temperatures oscillated in the whole occident of the country between the 21 and 23 °C. The dawn of the 28 was notably cold toward the interior of the Havana - Matanzas plain, with minimum temperatures of 7,2 °C at Indio Hatuey, 7,4 °C at Bainoa, 9,1°C at Jovellanos and 9,8 °C at Batabanó.

Two fronts affected the country in February, one the day 5 and the other one the 8, the first one stationed over the oriental provinces and produced some rainfall in that region the days 7 and 8, while the last one caused the dawn of the day 11 to be the coldest in the winter season that is analyzed. The combination of clear skies, the wind in calm and strong cold advection, produced notably cold temperatures in several towns, with the lowest value in 3,6 °C in Bainoa, province of Havana. This value is still far from the absolute record of minimum temperature of the country (0,6 °C), occurred on February 18 1996 in the same station of Bainoa. Among other remarkable registrations that day there are: 5,0 °C at Indio Hatuey and Tapaste, 6,3 °C at Güines and 6,5 at Camilo Cienfuegos, province of Ciego de Avila. On the other hand, at Casablanca the meteorological station of the capital, the thermometer descended to 12,6 °C, what turned out to be the lowest registration in the season at this station.

As it was already mentioned, Cuba was affected by no cold fronts in the month of March and was not until April 5th that another front system arrived to the occident of the island, that is to say, during 55 days, in full winter season, no arrival took place of a cold front to the country.

The last front system arrived on April 9th, it was classified as weak and it had the peculiarity that affected only the provinces of City of Havana and Matanzas.

Another matter to analyze in each winter season is the occurrence of winds from the south region on the western half of the country. These winds were called " southerns " by Rodríguez and Ballester (1985). They take place fundamentally due to the influence of the extratropical hurricanes that move on the gulf of Mexico or adjacent states of North America or to the interaction of the extratropical lows with the Azores-Bermuda anticyclone, conditions that cause the barometric gradient on the western half of Cuba to intensify.

This winter season was characterized by the low occurrence of " southerns ", with just two cases against a historical average of five. After the high frequency observed among the seasons 1995-1996 and 1997-1998 (33 cases in total), two seasons followed with low occurrence of " southerns ", that of 1998-1999 and the present one, with a total of two " southerns " each. This fact is not very common, since it has only been observed in the seasons 1920-1921 and 1921-1922 with four cases, in those of 1921-1922 and 1922-1923 with three cases, in those of 1949-1950 and 1950-1951 with four cases and in those of 1954-1954 and 1954-1955 with three cases.

In the current season the first case registered was classified as moderate and it occurred the days 29th and 30th of March, registering a maximum gust of 69 km/h near noon of the 30th. The second event was classified as strong and it took place on April 24 and 25, with a maximum gust of 83 km/h the 24 by noon.

Chart 3 is presented next, in which the great deficit of " southerns " in this season can be appreciated.

Chart 3. Historical monthly mean Frequency of " southerns " and the behavior during the winter season 1999-2000.

Season.	Sep.	Oct.	Nov.	Dec.	Jan.	Feb.	Mar.	Apr.	May.	Total
1918-1919 1998-1999	0.03	0.04	0.1	0.3	0.6	1.1	1.5	0.9	0.3	4.9
1999-2000	0	0	0	0	0	0	1	1	0	2

Conclusions y Acknoledgements