The Year's Weather - 1998

    It was the warmest year since records began in 1884. The annual mean temperature was 24.0 degrees, 0.2 degrees higher than the previous record set in 1966. The annual mean daily minimum temperature of 22.1 degrees was also the highest on record. The high temperatures were the result of relatively weak monsoon in the winter months. Under the influence of the El Nino effect in the first half of the year, the typhoon season started exceptionally late. The first tropical cyclone warning signal was hoisted on 9 August, the latest date for hoisting this signal in post-war years. Altogether, five tropical cyclones necessitated the hoisting of warning signals in the year. The annual total rainfall recorded at the Observatory was 2564.6 millimetres, 16 per cent above normal. The Black Rainstorm Signal was issued once on 9 June when a record daily rainfall for June of 411.3 millimetres was received. The mean cloud amount of 73 percent was the fourth highest on record.

    January 1998 was slightly warmer than normal with above average rainfall.

    It was warm and very wet in February. The monthly rainfall of 153.7 millimetres was nearly three times the normal figure and was the sixth highest for the month.

    The warm weather continued into March. In particular, 7 and 8 March were extremely humid and foggy and these conditions caused severe delay and diversion of many international flights.

    April 1998 was the warmest April on record. Late-season cold surges were notably absent and temperatures stayed at or above 20 degrees on all but one day. The Amber as well as the Red Rainstorm Warning Signals were issued for the first time this year on 12 and 26 April respectively.

    May was again warmer than normal and the month saw slightly above average rainfall.

    Over twice the average rainfall was recorded in June making it the fifth wettest June on record. 411.3 millimetres of rain fell on 9 June,the highest for any day in June, and necessitated the issuance of the Black Rainstorm Warning Signal for the first time in the year. On that day, various rainstorm warnings were continuously in force for more than 18 hours, the longest since the warning system was introduced in 1992. Over 400 millimetres of rainfall were recorded in most parts of Kowloon and over 500 millimetres in Sai Kung. 118 cases of flooding and 45 cases of landslips were reported.

    The first half of the year was very unusual in that not a single tropical cyclone was found over the entire western North Pacific and the South China Sea. This broke all records since 1946.

    In sharp contrast to the very wet six months from January to June, July was dry and hot. July saw the first tropical cyclone Nichole in the South China Sea. However, she did not affect Hong Kong.

    Temperatures for the rest of 1998 were significantly higher than normal.

    In August, both the mean temperature of 29.5 degrees and the mean minimum temperature of 27.4 degrees equalled the highest records set in August 1990. Two tropical cyclones affected Hong Kong and the first signal of the year was hoisted on 9 August, the latest date for hoisting this signal in post-war years.

    The mean minimum temperature of 26.2 degrees in September was the fourth highest for the month and the Standby Signal No. 1 was hoisted only once.

    In October, the mean temperature of 26.1 degrees and the mean minimum temperature of 24.3 degrees were the third and second highest respectively for October. Two tropical cyclones necessitated the hoisting of warning signals in the month.

    Temperature records were broken again in November. Both the monthly mean temperature of 23.2 degrees and the mean minimum temperature of 21.4 degrees exceeded previous highs.

    In December, the mean temperature of 19.1 degrees and the mean minimum temperature of 17.4 degrees were the sixth and the third highest respectively on record for the month.

Summary of Meteorological Observations in Hong Kong, 1998
 

Month	Mean Pressure (hPa)	Air     Temperature			Mean Dew Point Temperature (deg. C)	Mean Relative Humidity (%)	Mean Amount of Cloud (%)	Total Rainfall (mm)
		Mean Daily Maximum (deg. C)	Mean (deg. C)	Mean Daily Minimum (deg. C)
January	1019.2	19.0	16.8	15.0	13.4	81	77	48.9
February	1018.1	19.3	17.2	15.2	14.3	83	86	153.7
March	1016.3	21.4	19.1	17.2	16.5	86	86	55.3
April	1013.0	27.4	24.8	22.9	21.3	82	78	237.1
May	1009.6	29.0	26.8	25.0	23.8	84	76	335.2
June	1006.9	30.3	28.3	26.6	25.3	84	87	814.5
July	1007.3	31.5	29.0	27.1	25.2	80	78	267.2
August	1008.3	32.1	29.5	27.4	25.4	79	65	245.4
September	1008.3	30.1	27.8	26.2	23.3	78	64	230.9
October	1011.6	28.3	26.1	24.3	20.1	71	59	133.9
November	1015.6	25.3	23.2	21.4	17.7	72	60	28.8
December	1019.6	21.3	19.1	17.4	13.2	70	61	13.7
Mean/Total	1012.8	26.3	24.0	22.1	20.0	79	73	2564.6
Normal	1012.9	25.7	23.0	20.9	18.6	77	65	2214.3
Station	Hong  Kong  Observatory

Month	Total Bright Sunshine (hours)	Mean Daily Global Solar Radiation (MJ/m2)	Total Evaporation (mm)	Prevailing Wind Direction (degrees)	Mean Wind Speed (km/h)
January	86.0	7.73	53.5	060	28.9
February	56.4	7.11	47.0	020	24.6
March	82.2	9.93	64.9	050	25.8
April	123.4	13.16	95.4	060	17.9
May	139.3	13.56	103.9	100	18.7
June	90.0	11.05	82.0	210	24.7
July	222.1	18.02	150.4	230	23.2
August	234.3	17.30	147.8	230	16.5
September	159.9	13.70	117.6	080	23.3
October	180.4	13.18	124.7	080	30.4
November	137.5	11.09	91.2	070	26.1
December	153.8	10.21	80.3	010	26.9
Mean/Total	1665.3	12.21	1158.7	070	23.9
Normal	1948.1	14.46	1528.8	080	22.6
Station	King's  Park			Waglan  Island^