METEOROLOGICAL SERVICES

Transcription

1 REPUBLIC OF MAURITIUS METEOROLOGICAL SERVICES MONTHLY BULLETIN of CLIMATOLOGICAL SUMMARIES JUNE 2011 September 2011

2 Contents Introduction 1-2 Map of Mauritius / Area of responsibility 3 Weather Suary 4 Rainfall in Mauritius 5-10 Mean Monthly Rainfall 11 Rainfall Analysis 12 Monthly Climatological Suaries 13 Monthly Agrometeorological Suaries 14 Monthly Synoptic Suaries 15 Mean Sea Surface Temperature 16 Surface Wind Rose 17 Upper Winds Observations 18

3 1. INTRODUCTION MONTHLY CLIMATOLOGICAL SUMMARIES For MAURITIUS, RODRIGUES AND OUTER ISLANDS Mauritius lies between Latitudes 19º58.8' and 20º31.7' South and Longitudes 57º18.0' and 57º46.5' East. Rodrigues lies between Latitudes 19º40' and 19º46' South and Longitudes 63º20' and 63º30' East about 650 km East of Mauritius. St. Brandon is a coral atoll situated around Latitude 16º27' South and Longitude 59º37' East about 450 km to the North-North-East of Mauritius. Agalega consists of two small islands between Latitudes 10º20' and 10º29' South and Longitudes 56º34' and 56º42' East, about 1050 km almost North of Mauritius. Monthly climatological data presented in this issue are based on daily observations of various meteorological parameters recorded in Mauritius, Rodrigues, St. Brandon and Agalega. 2. STATIONS Synoptic Weather Stations Synoptic weather stations perform synoptic weather observations; that is, surface weather observations at fixed intervals of time of sky cover, cloud base height, atmospheric pressure, temperature, dew point, wind speed and direction, precipitation amount, horizontal visibility and other special phenomena. The Mauritius Meteorological Services maintains six synoptic stations: Vacoas (20º18'S, 57º30'E) WMO Station number 61995, and Plaisance (20º26'S, 57º41'E) WMO Station number 61990, in Mauritius. Pointe Canon (19º41'S, 63º25'E) WMO Station number and Plaine Corail (19º41'S, 63º45'E) WMO Station number 61989, in Rodrigues. Raphael Island, located at 16º27'S and 59º37 E WMO Station number 61986, in St Brandon. Agalega located at 10º21'S 56º35'E, WMO Station number 61974, in North Island. Climatological Stations Climatological stations record such parameters as: maximum and minimum temperatures, rainfall and some other elements like atmospheric pressure, humidity, soil temperatures, sunshine and wind. The Mauritius Meteorological Services has a network of 26 climatological stations in Mauritius. Agrometeorological Stations The agrometeorological stations monitor standard climatological data that are of interest to agriculture, livestock breeding and forestry. These stations monitor the following parameters, evaporation, humidity, rainfall, sunshine duration, temperature and wind. The Mauritius Sugar Industry Research Institute manages four such stations in Mauritius with the collaboration of the Meteorological Services. Savannah Sugar Estate maintains another station at La Baraque. 3. INSTRUMENTS IN USE AT METEOROLOGICAL STATIONS: Raingauges Ordinary raingauges with outer rim of diameter cm together with ordinary laboratory cylinders graduated in cubic centimeters are being used to measure rainfall at most stations. Readings are taken at 0700 hours daily. Fourteen stations are equipped with rain recorders, which provide rainfall intensities.

4 Thermometers and Hygrometers Ordinary mercury in glass thermometers are used to measure dry, wet bulb and soil temperatures. Maximum and Minimum temperatures are measured by other appropriate thermometers. Thermohygrographs have been installed at four stations. Anemometers Eight Dines anemometers provide wind data at the following sites in Mauritius: Digue Seche, FUEL, Medine, Mon Desert Alma, Pamplemousses, Plaisance, Quatre Bornes and Vacoas. There is also one Dines anemometer at Pointe Canon in Rodrigues. At Agalega, St. Brandon and Plaine Corail airport in Rodrigues, wind is measured by a cup anemometer. Sunshine Recorders Campbell Stokes sunshine recorders have been installed at twenty-one sites in Mauritius. One station at Rodrigues and one at Agalega are also in operations. Evaporation Pans Modified US Class A pans are used to measure daily evaporation amount at 14 stations in Mauritius and one station, Pointe Canon, in Rodrigues. Barometers Mercury barometers, digital barometers and aneroid barographs are used at all synoptic stations to measure atmospheric pressure. Tide Gauges Sea level is monitored using tide gauges installed at Port Louis and Port Mathurin. In January 2009, a new tide gauge was installed in Agalega and another one at Blue Bay. Upper Air monitoring Equipment Upper Air observations are carried out daily at Vacoas. A GPS system using the SR2K2 software ICAR-IGOR pro 5.03 is used to compute upper level winds. Automatic Weather Stations 20 automatic weather stations have been installed at different sites over the island. Weather parameters observed by these automatic weather stations are: humidity, rainfall, temperature, wind and pressure. Three stations, namely Vacoas, Bain Boeuf and St Felix also record global solar radiation. There are also two stations in Rodrigues which measure all the above six parameters. 4. METEOROLOGICAL SUMMARIES Monthly suaries of meteorological observations in the form of mean totals, extreme values with date of occurrence and departure from long term mean are presented in this issue for various climate parameters of stations located in Mauritius, Rodrigues and the Outer Islands.

5 Map of Mauritius showing Contours and Basin N Mon Choisy 40 NN 160 Pamplemousses Digue Seche NN Contours: Height (metres) Regional Delimitations : North NW Fort William NW : North West EE : East WW : West CW : Central Plateau (Windward) Medine WW 320 Reduit Alma 440 CL 440 Vacoas 320 Sans Souci FUEL 160 EE Beau Champ CL : Central Plateau (Leeward) SE : South East SS : South SW : South West 600 CW Ferney SE Le Morne SW Bel Ombre SS 160 Britannia Plaisance 40 Scale 1:300,000 Seychelles 05º S Diego Garcia Agalega 10º S Diego Suarez Tromelin St. Brandon 15º S J. de Nova Tamatave Tana Reunion Mauritius Rodrigues 20º S Europa Fort Dauphin 25º S 45º E 50º E 55º E 60º E 65º E 70º E 75º E 80º E 85º E 90º E Area of responsibility of the Republic of Mauritius for the naming of tropical Cyclones

6 WEATHER SUMMARY - JUNE 2011 During the month of June, 8 anticyclones crossed the Indian Ocean. However, temperatures remained warmer than normal over the Mascarenes since most of the anticyclones were either weak in intensity or they passed far to the south and there was little cold air advection over the region. During the second week of June, the approach of a subtropical low from the south west caused light northwesterly winds to blow over the island and conditions became very warm and sultry. This low passed far to the south of Mauritius, however the trough associated to it crossed the island on June 13 and caused widespread precipitation. Most of the stations recorded above 50 of rainfall in 24 hours. The instability was further enhanced by the presence of the jet core lying on the pole ward side of the island and a mid-tropospheric trough which was oscillating in the vicinity of Mauritius. On June 15 favourable upper level atmospheric conditions together with the warm and moist airstream, triggered thunderstorms over Moka region. Thereafter atmospheric conditions became less favourable for precipitation and a slight drop in temperatures were recorded following the passage of a frontal system on June 19. However, the approach of a complex pressure area to the south of Madagascar caused the mercury level to shoot up again. This low moved towards the south east, but it was rapidly replaced by another one advecting from the west. Thus, the presence of these lows to the south west of the Mascarenes forced the anticyclones to track further south and then eventually emerged in the mid-indian ocean; without directly influencing the Mauritius. As such, temperatures remained above the seasonal mean. The total rainfall for June was 151 over Mauritius, representing 132 % of the normal for the month. Over Rodrigues accumulated precipitation was slightly below the seasonal mean. Pointe Canon recorded 69 of rainfall which represents 89 % of the monthly mean. Outer-Islands Agalega and St-Brandon were deficient in precipitation with the accumulated rainfall amounting to 42% and 70% respectively. The mean sea level pressure was slightly below the long-term mean at all stations, except at Agalega it was slightly above the mean. Bright sunshine hour was close to normal at Vacoas whereas at Rodrigues it was slightly below the mean.

7 STATIONS RAINFALL IN MAURITIUS --- Location Alt m Total Dep from Normal 1 JUNE 2011 No of days on which RR reached or exceeded Maximum Rainfall in 24 hr REGION : NORTH Cap Malheureux Mont Choisy Mapou Cour St. Antoine (Cour Usine) Bain Boeuf (AWS) Digue Seche Solitude (La Plaine) Mon Loisir Rouillard (AWS) Mon Loisir Rouillard Fond du Sac Mapou (BVM) Fleurant Forbach (BVM) Belle Vue (BVM) Labourdonnais NPIPP Mauricia ( B.V.M. ) Schoenfield St. Andre (AG22) Mon Choix Beau Plan Beau Sejour Champ Rose Pamplemousses ( MSIRI ) Maison Blanche Mon Loisir S.E The Mount Esperance (Beau Plan) Belle Vue Maurel Mon Piton Antoinette Grande Rosalie Mon Songe California Industrie ( Cour ) REGION: NORTH WEST Cantin Richeterre (Versailles) Cite La Cure Fort William ( P.L.H.R. ) * Often - Data not available aws: automatic weather station

8 STATIONS RAINFALL IN MAURITIUS --- Location Alt m Total Dep from Normal JUNE 2011 No of days on which RR reached or exceeded Maximum Rainfall in 24 hr REGION : NORTH WEST Port Louis (aws) Le Souvenir Amitie (2) Notre Dame Domaine Les Pailles (aws) Valton Beau Fonds REGION : WEST Pointe aux Sables Albion (Medine) Albion (aws) Balisage Petite Riviere Noire Case Noyale Richelieu Gros Cailloux St Antoine (Medine) La Mecque La Ferme Belle Vue (Medine) Medine (Medine) Palmyre (No.1) Clarens (Medine) La Verette Magenta Tamarin ( Estate ) Yemen Beaux Songes (aws) Chebel Bagatelle (Medine) Le Bosquet Barkly ( Exp. Station ) Le Reduit ( MSIRI ) La Chaumiere (R.B. No1) Trianon (Estate) Corps de Garde Beaux Songes (Medine) Pierrefonds Bassin REGION : SOUTH WEST La Gaulette Le Morne (AWS) Le Morne Brabant Coteau Gambier * Often - Data not available aws: automatic weather station

9 STATIONS RAINFALL IN MAURITIUS --- Location Alt m Total Dep. from Normal JUNE 2011 No of days on which RR reached or exceeded Maximum Rainfall in 24 hr REGION : SOUTH WEST Terres Couleurs Chamarel ( Estate ) Plaine Champagne REGION : SOUTH Beau Champs (B.O) Bel Ombre St Felix (Factory) Terracine Souillac (aws) Choisy Estate Frederica Canal Vacoas Ste. Marie Fontenelle St. Aubin Riviere des Anguilles Bel Air (Benares) Union Savanne Val Riche Luchon Satana Combo Bois Sec (U) Bois Cheri Pradier Grand Bassin (aws) REGION : SOUTH EAST Pointe aux Feuilles Bestel Camizzard Providence (F) Ferney Le Vallon Campement Ste Helene Beau Vallon (Cour) Terre Rocheuse (BVWest) Terre Rocheuse (RLChaux) Mon Desert ( M.D.M.T. ) Riviere Tabac Florine * Often - Data not available aws: automatic weather station

10 STATIONS REGION : SOUTH EAST JUNE in 24 hr Cent Gaulettes Riviere des Creoles Riche En Eau Riche En Eau (aws) Astroea (R.E.E) Courbevoie Mon Tresor Plaisance Gros Bois Union Vale Sauveterre La Baraque Colmar Siding Benares Savinia Chateau Benares Savanah St. Felix (B.A.S.E) Benares Montagne Ronde Eau Bleu Tostee Mont Vernon Deux Bras Hewetson St. Avold Joli Bois Britannia Riche Bois (B) REGION : EAST RAINFALL IN MAURITIUS --- Location Alt m Total Dep. from Normal No of days on which RR reached or exceeded Maximum Rainfall Haute Rive Bras D'Eau Providence (P.de Flacq) Bassin Requins Constance Belle Mare Mare La Chaux Palmar (aws) Beau Rivage Beau Champ - Littoral Grande Retraite (La Retraite) Allendy (BV) Argy * Often - Data not available aws: automatic weather station

11 STATIONS REGION : EAST RAINFALL IN MAURITIUS --- Location Alt m Total Dep from Normal JUNE 2011 No of days on which RR reached or exceeded Maximum Rainfall in 24 hr FUEL ( UNION ) La Gaiete Queen Victoria Queen Victoria (aws) Belle Etoile Naye Caroline Clemencia Belle Rose (DRBC) La Lucie Terre Franche (DRBC) Grand Port (DRBC) Trois Ilots La Louise (T. Rocheuse) Olivia Beau Vallon (DRBC) Etoile Belle Rive (DRBC) Rich Fund Unite Gibraltar Bel Etang Sans Souci REGION : CENTRAL PLATEAU WINDWARD Bonne Veine (MDA) Providence Providence (aws) Grosse Roche Piton du Milieu Eau Bleue Dam Union Park ( MSIRI ) La Flora Nouvelle Decouverte(aws) Belle Rive (1E) Belle Rive ( 2E ) XVI Mile(Mon Bois)(aws) REGION : CENTRAL PLATEAU LEEWARD Beau Bois (MDA) Mon Desert Alma Minissy (MDA) Minissy (H) Moka (aws) Cote d'or Bagatelle (H) * Often - Data not available aws: automatic weather station

12 STATIONS REGION : CENTRAL PLATEAU LEEWARD RAINFALL IN MAURITIUS --- Location Alt. m Total Dep from Normal JUNE 2011 No of days on which RR reached or exceeded Maximum Rainfall in 24 hr Quatre Bornes ( Michaud ) Highlands Vacoas Burgos Reunion Holyrood Moon Alma Valetta Hermitage Belle Rive (MSIRI) Henrietta Trou aux Cerfs (aws) La Marie Tamarin ( Res. ) Bonne Fin Good End Mare Longue Arnaud Arnaud (aws) Petrin REGION : RODRIGUES Pointe Canon Corail Airport Citronelle (aws) REGION : AGALEGA ISLANDS Agalega 10º 21' S º 35' E REGION : ST. BRANDON ISLANDS St. Brandon 16º 27' S º 37' E * Often - Data not available aws: automatic weather station

13 MEAN MONTHLY RAINFALL JUNE 2011 Isohyetal Analysis ( ) REGION NORTH CENTRAL PLATEAU SOUTH SOUTH NORTH EAST WEST SOUTH HEIGHT WEST Windward Leeward EAST WEST > Total Mean Mean Rainfall over Mauritius : 151 Percentage Rainfall of Long Term Mean : 131 % June 2011 was a rather wet month with 151 of rainfall representing 131 % of the long-term mean of The first 12 days of the month were relatively dry except for little rainfall on the 7 due to weak perturbation in the easterlies. The first significant rainfall was recorded between the 13 and 14 and this was associated with an active instability line. Thereon, from the perturbed trades maintained a wet condition and this was followed by clouds associated with a frontal system from the From the clouds in the easterlies again resulted into scattered rainfall and this situation repeated on the 28. Besides the windward side of the Central Plateau and the South, most regions of the island had slightly above to well above normal precipitation going up to 358 % to the West, which was actually the highest percentage of rainfall. Else, the windward side of the Central Plateau recorded the highest amount namely 196.

14 RAINFALL ANALYSIS - JUNE 2011 Isohyets in millimetres Expressed as a percentage of the mean Mon Choisy Cap Malheureux 100 Mon Choisy Cap Malheureux 100 Digue Seche Digue Seche Pamplemousses 150 Pamplemousses Fort William Fort William Reduit Alma 200 F U E L Reduit Alma F U E L Medine Quatre Bornes 250 Beau Champs Medine Quatre Bornes Beau Champs Petite Riviere Noire Trou aux Cerfs Vacoas 200 Le Val Sans Souci Ferney 100 Petite Riviere Noire Vacoas Trou aux Cerfs Le Val Sans Souci Ferney Arnaud Rose Belle Arnaud Rose Belle Le Morne Plaine Champagne 150 Britannia Plaisance Le Morne Plaine Champagne Britannia Plaisance Bel Ombre Bel Ombre Souillac Souillac

15 Mean Maximum Mean Minimum Mean Temperature Highest Maximum Lowest Minimum Mean Realtive Humidity ( AM ) Mean Relative Humidity ( PM ) Lowest Relative Humidity Total Evaporation Daily Max. Evaporation Total Sunshine Mean Daily Daily Maximum Depth 30cm Depth 50cm Depth 100cm STATIONS TEMPERATURE (ºC) METEOROLOGICAL SUMMARIES JUNE 2011 Monthly Data from Climatological Stations RELATIVE HUMIDITY ( % ) EVAPORATION BRIGHT SUNSHINE MEAN SOIL ( ) ( Hrs ) TEMP (ºC) Fort-William DigueSeche Labourdonnais NPIPP Constance FUEL Sans Souci Riche en Eau Beau Vallon Sauveterre , , 5 Britannia , 18 Bois Cheri Tea Est Le Morne (aws) Richelieu Medine Barkly Exp. Station Case Noyale Mon Desert Alma Quatre Bornes Trou aux Cerfs (aws) * Often - Data not available aws: automatic weather station

16 Mean Maximum Mean Minimum Mean Temperature Highest Maximum Lowest Minimum Mean Realtive Humidity ( AM ) Mean Relative Humidity ( PM ) Lowest Relative Humidity Total Evaporation Daily Max. Evaporation Total Sunshine Mean Daily Daily Maximum Depth 30cm Depth 50cm Depth 100cm STATIONS METEOROLOGICAL SUMMARIES JUNE 2011 Monthly Data from Agrometeorological Stations TEMPERATURE RELATIVE EVAPORATION BRIGHT SUNSHINE MEAN SOIL (ºC) HUMIDITY ( % ) ( ) ( Hrs ) TEMP (ºC) Pamplemousses Reduit Belle Rive Union Park La Baraque , * Often - Data not available

17 Mean Maximum Mean Minimum Mean Temperature Highest Maximum Lowest Minimum Mean Relative Humidity ( AM ) Mean Relative Humidity ( PM ) Mean Relative Humidity ** Difference from Normal Lowest Relative Humidity Mean MSL Pressure ** Difference from Normal Highest Mean MSL Pressure Lowest Mean MSL Pressure Total Sunshine Mean Daily Daily Maximum Total Evaporation Daily Max. Evaporation STATIONS TEMPERATURE (ºC) METEOROLOGICAL SUMMARIES JUNE 2011 Monthly Data from Synoptic Stations RELATIVE HUMIDITY BAROMETRIC PRESSURE BRIGHT SUNSHINE EVAPORATION ( % ) ( hpa ) ( Hrs ) ( ) Plaisance Vacoas *** , Rodrigues St.Brandon Agalega ,5,21 * Often - Data not available ** Mean from main synoptic hours *** Station level pressure

18 MEAN SEA SURFACE TEMPERATURE - JUNE C 26 C 24 C 22 C 20 C 18 C

19 SURFACE WIND - JUNE 2011 Wind Rose (% Frequency) PLAISANCE VACOAS Calm Calm Mean Wind Speed (ms -1 ) 3.3 Mean Wind Speed (ms -1 ) 3.1 Maximum Gust (ms -1 ) 13.0 Maximum Gust (ms -1 ) FORT - WILLIAM ST. BRANDON 1 12 Calm Calm 2 58 DATA NOT AVAILABLE 5 22 Mean Wind Speed (ms -1 ) Mean Wind Speed (ms -1 ) 5.3 Maximum Gust (ms -1 ) Maximum Gust (ms -1 ) - - RODRIGUES (Pte. Canon) AGALEGA 2 6 Calm 1 34 Calm Mean Wind Speed (ms -1 ) 5.3 Mean Wind Speed (ms -1 ) 4.4 Maximum Gust (ms -1 ) 20.8 Maximum Gust (ms -1 ) FREQ:

20 UPPER WIND OBSERVATIONS - JUNE 2011 Vector Mean LEVEL 850 hpa 700 hpa 500 hpa 400 hpa 300 hpa 250 hpa 200 hpa 150 hpa 100 hpa 1500 m 3000 m 5700 m 7500 m 9600 m m m m m STATION Deg kt Deg kt Deg kt Deg kt Deg kt Deg kt Deg kt Deg kt Deg kt VACOAS RODRIGUES Maximum Wind LEVEL 850 hpa 700 hpa 500 hpa 400 hpa 300 hpa 250 hpa 200 hpa 150 hpa 100 hpa 1500 m 3000 m 5700 m 7500 m 9600 m m m m m STATION Deg kt Deg kt Deg kt Deg kt Deg kt Deg kt Deg kt Deg kt Deg kt VACOAS RODRIGUES Absolute Maximum Wind STATION Deg kt Height (m) VACOAS RODRIGUES Data not available