RESUME OF THE 1998-1999 WINTER SEASON IN CUBA

Season analysis

During this season 15 fronts arrived to the National territory, making it classify as a little active one, if we take into account that the historical average is 19,8 with a standard deviation of ± 4,9. A review of the cold fronts record kept at the Forecast Department dating from the 1916-1917 season shows that the current season is the eighth with 15 fronts. This event occurred the last time in the season of 1992-1993. On 6 winter seasons 14 fronts arrived. In the seasons of 1916-1917 and 1918-1919 only 13 arrived and in the seasons of 1917-1918 and 1933-1934 12 fronts arrived. The least active season was the 1996-1997 one with only 11 fronts while the most active was the 1976-1977 one with 35 cold fronts.

On Table 1 the arrival date and classification of cold fronts that affected Cuba during the 1998-1999 winter season is presented.

Attending to the insular condition and the geographical position of Cuba, cold fronts are classified according to the speed of the north winds blowing immediately after the frontal line as follows:

Weak

Wind speed less than 35 km/h.

Moderate

Wind speed between 36 and 55 km/h.

Strong

Wind speed above 55 km/h.

Table 1. Number of cold front, date of arrival and classification upon arrival to Cuba during the winter season of 1998-1999.

Number	Date of arrival	Classification
1	October 23rd 1998	Moderate
2	November 5th 1998	Weak (WC)
3	December 14th 1998	Weak (WC)
4	December 30th 1998	Weak
5	January 4th 1999	Weak (WC)
6	January 10th 1999	Weak (WC)
7	January 24th 1999	Weak
8	February 13th 1999	Moderate (WC)
9	February 19th 1999	Weak
10	March 2nd 1999	Moderate (WC)
11	March 4th 1999	Weak
12	March 14th 1999	Moderate (WC)
13	March 22nd 1999	Weak (NC)
14	April 17th 1999	Weak
15	May 1st 1999	Weak (WC)

Note: In table 1 (WC) means that the front ran across the whole Country, while (NC) means it only affected the North coast of the Western region.

Comparisons of Table 1 with historical records reveal the following characteristics:

Amongst all cold fronts reaching the Cuban archipelago this season, 11 (73%) were ranked as weak and the remaining 4 (27%) as moderate. Just like in the two latest winter seasons, no strong front arrived. Historically 48% of cold fronts arriving to Cuba are moderate, 42% are weak and 10% are strong.

During their displacement eastward over the National territory cold fronts get weaker, and on average, only half of those affecting the West part of the country reach the East part. Seven systems covered the whole territory this time for a 47% of the total, a figure close to the historical average.

Based on the Chronology developed by Rodriguez et al. (1984) and its further update at the Forecast Department of the Institute of Meteorology Table 2 was built.

Table 2. Amount of cold fronts that have affected Cuba by months since the 1916-1917 season until 1997-1998 and behavior in the last two seasons.

Season	Sep.	Oct.	Nov.	Dec.	Jan.	Feb.	Mar.	Apr.	May.	Jun.	Total
1916 1998	7	109	211	268	293	277	244	161	59	4	1633
Average	0,09	1,34	2,60	3,30	3,61	3,41	3,01	1,97	0,71	0,05	--
1997 1998	0	1	4	7	4	4	4	2	0	0	26
1998 1999	0	1	1	2	3	3	3	1	1	0	15

The 1998-1999 Winter season had a normal beginning with regard to the number of cold fronts affecting the territory, but November and December behaved below the historical average, while January, February, March and May showed numbers in agreement with it. April also lagged behind with only one front, while its average is of almost 2.

Brief description of frontal systems that reached Cuba