July Issued: August 6, 2016 Since : August 1980* Volume 37 : Issue 07

Transcription

1 FIJI METEOROLOGICAL SERVICE Private Mail Bag (NAP351) Nadi Airport, Fiji Ph: , Fax: Also online at Fiji Climate Summary July 216 ISO 91:28 certified Climate Services Issued: August 6, 216 Since : August 198* Volume 37 : Issue 7 1. IN BRIEF The month of July was considerably drier as rainfall producing systems have generally been displaced further north of the Fiji Group. However, a frontal system brought some relieving rainfall over the Western Division and northern parts of Vanua Levu towards the end of the month. The trend of dry conditions continued during the month with majority of the stations receiving below average to well below average rainfall. Fourteen out of the 26 recorded less than half of the normal July rainfall. The dryness was particularly notable over the Western Division and northern parts of Vanua Levu with extended periods of without any rainfall. Below average rainfall also extended to the Eastern Division. The past three months, that is, from May to July 216, have been considerably drier than usual across the country. During this period, rainfall ranged from 12 to 43% in the Western and Northern Divisions and generally between 53% to 84% in the Central and Eastern Divisions. Notably, 73% of the climate monitoring stations are currently in meteorological drought conditions on a 3 months timescale and 67% on 6 months timescale. Consequently, accumulated rainfall deficiencies would have started to affect shallow rooted crops, streams, creeks, wells and bore holes at majority of the places especially in the Western Division, Northern Division and small islands. The average maximum air temperatures were generally normal to above normal, with 15 out of the 21 stations recording anomalies.5 C (Table 2 & Figures 2-5). Significantly cool conditions were experienced from 18 th and 2 th, when most of the stations recorded the lowest daily minimum temperature for the month. Nadarivatu recorded 1.1 C on the 18 th, followed by Keiyasi with 11.1 C on the 2 th. A record high average maximum temperature for July was registered at Labasa Airport and Nabouwalu during the month, while a new high average minimum temperature was established at Ono-i-lau. 2. WEATHER PATTERNS July was dominated by transient troughs of low pressure, semi permanent high pressure systems and the broad southeast trade winds. For the first two days of July, a weak trough was over Fiji, causing showers over the eastern part of the country. The trough moved eastward overnight on the 2 nd as a southeast wind flow extended onto the group from the south. The southeast winds weakened on the 4 th as a trough moved onto Fiji but strengthened later on the 4 th as it slipped east of Fiji. The southeast winds prevailed till the 8 th before it weakened as the high pressure system receded and a fast moving trough approached Fiji from the southwest. The trough moved onto Fiji overnight on the 1 th causing showers over the eastern and interior parts of the larger islands. It eventually cleared the group overnight on the 11 th as a ridge of high pressure extended form the south. The ridge initially directed a south to southeasterly wind flow which prevailed till 18 th, which caused cool temperatures at night. The southeast wind flow slightly weakened overnight on the 18 th as a front moved onto the southern part of Fiji. The front eventually moved away from Fiji on the 19 th as a cool and dry southerly winds strengthened over the country. Cool southerly winds coupled with cloudless night caused night-time temperature to drop with Keiyasi recording an overnight minimum of 11.1 C on 2 th. The winds eventually turned southeasterly later on the 21 st and prevailed till the 29 th. Towards the later part of the month, the southeast winds receded as a frontal system approached Fiji from the southwest and affected the country later on the 31 st. Showers was recorded in some parts of Fiji with Viwa recording the highest of 5.2mm. Rotuma s weather was largely influenced by the South Pacific Convergence Zone and the southeast winds which produced some showers, with the highest of 13.8mm recorded on the 3 th. Overnight temperature were never lower than 23 C. *Previously known as the Fiji Islands Weather Summary and Monthly Weather Summary 1

2 3. RAINFALL The month of July was considerably drier, as rainfall producing systems have generally been displaced further north of the Fiji Group. However, a frontal system brought some relieving rainfall over the Western Division and northern parts of Vanua Levu towards the end of the month. Lautoka Mill was the driest station during the month, with 6mm of rainfall, followed by Yasawa-i-rara, Dreketi, Rarawai Mill, and Nadi Airport with 9mm, 1mm, 12mm and 13mm, respectively. In contrast, Monasavu registered the highest total monthly rainfall of 252mm, followed by Tokotoko, Udu Point and Laucala Bay with 169mm, 9mm, and 79mm, respectively. Trend of dry conditions continued in July with majority of the stations receiving below average to well below average rainfall. Out of the 26 stations, 11 received well below average rainfall, 1 below average, 4 average, while Monasavu was the only station to register above average rainfall (Figures 1-4 & Table 2). The dryness was particularly notable over the Western Division and northern parts of Vanua Levu with extended periods of without rainfall. Consequently, Labasa Airport and Lautoka Mill recorded only 1 rain day (rainfall.1mm) during the month, followed by Nadi Airport and Viwa with 2 and Rarawai Mill with 3 rain days. The frontal system that traversed over the country towards the end of the month brought some relief from the dry conditions at some stations. Labasa Airport registered 29mm of rainfall on the 3 th, with Dreketi and Seaqaqa both receiving 7mm of rainfall on the same day. Viwa, Nacocolevu, Nadi Airport, Rarawai Mill and Lautoka Mill recorded 5mm, 29mm, 13mm, 12mm and 6mm of rainfall on the 31 st, respectively. On the 3 month timescale, Koronivia, Labasa Airport, Lakeba, Lautoka, Matei Airfield, Nadi Airport, Nausori, Navua, Rarawai, Savusavu, Seaqaqa, Suva, Udu Point, Vunisea, Yasawa and Rotuma were in meteorological drought, while Dobuilevu, Ono-i-Lau, Penang and Tavua are currently in meteorological drought warning stage. On the 6 months time scale, Koronivia, Labasa, Lakeba, Nausori, Navua, Penang, Seaqaqa, Suva, Udu Point, Vunisea, Yasawa and Rotuma are in meteorological drought. Consequently, accumulated rainfall deficiencies would have started to affect shallow rooted crops, streams, creeks, wells and boreholes at majority of the places especially in the Western Division, Northern Division and the smaller islands. Figure 1 Normal: Long term average from 1971 to 2 Average: Rainfall between 8 to 119% Well Below Average: Rainfall less than 4% of normal Above Average: Rainfall between 12 to 199% Below Average: Rainfall between 4 to 79% Well Above Average: Rainfall greater than or equal to 2% of normal Rain Day: Rainfall.1mm 2

3 4. AIR TEMPERATURES A. Maximum Daytime Air Temperatures The average maximum air temperatures were generally normal to above normal, with 14 out of the 21 stations recording anomalies.5 C, 6 within ±.5 C and Tokotoko was the only station to record a significant negative anomaly (-.7 C) (Table 2 & Figures 2-5). The warmest days on average was at Labasa Airport with 31.5 C, followed by Rarawai Mill with 3.9 C and Keiyasi with 29.9 C. On the other hand, coolest maximum temperature on average was registered at Monasavu with 21.7 C, and Nadarivatu with 22.6 C. Unusually hot conditions were experienced on occasions during the month. The highest daily maximum temperature of 33.5 C was recorded at Rarawai Mill on the 27 th, followed by Keiyasi with 33.3 C on the 31 st. On the contrary, cool daytime temperatures were observed at some of the stations on instances. Monasavu recorded maximum temperature as low as 17.7 C on the 21 st, followed by Nadarivatu with 19.1 C on the 17 th. The mean monthly maximum temperatures were warmer than normal at a number of stations, with the greatest departure from the normal observed at Labasa Airport (+2.3 C), followed by Nabouwalu (+1.5 C) and Viwa (+1.4 C). A record high average maximum temperature for July was registered at Labasa Airport and Nabouwalu during the month (Table 1 below). B. Minimum Night-time Air Temperatures The night-time air temperatures were also generally normal to above normal, with 9 out of the 21 stations recording average minimum temperatures.5 C, 9 within ±.5 C, and C (Table 2 & Figures 2-5). The coolest nights on average was at Nadarivatu with 15.3 C, followed by Monasavu with 15.9 C and Keiyasi with 16.2 C. Conversely, the warmest night on average was experienced at Rotuma with 24.8 C, followed by Viwa with 23.1 C. Significantly cool conditions were experienced between 18 th to 2 th, when more than half of the stations recorded their lowest daily night-time temperature for the month. Nadarivatu recorded 1.1 C on the 18 th, followed by Keiyasi with 11.1 C on the 2 th. On the other hand, Rotuma recorded night-time temperature as high as 26.3 C on the 6 th, followed by Viwa with 25. C on the 5 th. The most notable positive mean monthly minimum air temperature departure from the normal of +1.8 C was recorded at Tokotoko, while the most significant negative anomaly of 1.6 C was registered at Labasa Airport. A new high average minimum temperature record for July was established at Ono-i-lau during the month (Table 1). TABLE 1. CLIMATE RECORDS ESTABLISHED IN JULY 216 Element Station Observed (record) On Rank Previous (record) Year Records Began Mean Maximum Temperature Labasa Airport 31.5 o C - Mean Maximum Temperature Nabouwalu 27.8 o C - Mean Minimum Temperature Ono-i-lau 31.4 o C - New High New High New High 3.4 o C o C o C Note: All comparisons in this summary are with respect to Climatic Normals. This is defined to be the average climate condition over a 3-year period. Fiji uses period as its climatic normal period, unless otherwise stated. 3

4 TABLE 2. DAILY CLIMATE REPORTING SITES: SUMMARY FOR JULY 216 RAINFALL AIR TEMPERATURES SUNSHINE TOTAL RAIN MAX. AVERAGE DAILY EXTREME TOTAL * DAYS FALL MAX. # MIN. # MAX. MIN. * MM % + MM ON C C C C C ON C ON HRS % NADI AIRPORT SUVA/LAUCALA BAY NACOCOLEVU ROTUMA VIWA UDU POINT SAVUSAVU AIRFIELD LABASA AIRFIELD NABOUWALU KORONIVIA NAUSORI AIRPORT NAVUA/TOKOTOKO MONASAVU LAUTOKA AES BA/RARAWAI MILL PENANG MILL MATEI AIRFIELD VANUABALAVU U/S LAKEBA NO OBSERVATION LEVUKA VUNISEA MATUKU ONO-I-LAU DREKETI SEAQAQA DOBUILEVU YASAWA-I-RARA VATUKOULA INSUFFICIENT OBSERVATIONS TEMPERATURE( C)HUMIDITY WIND SUN RAD DRY WET RH% VP %OF MJ/ MEAN (AVERAGE AT 9AM) KT POS SQ.M NADI AIRPORT SUVA/LAUCALA BAY NACOCOLEVU ROTUMA VIWA UDU POINT SAVUSAVU AIRFIELD LABASA AIRFIELD NABOUWALU KORONIVIA NAUSORI AIRPORT NAVUA/TOKOTOKO MONASAVU LAUTOKA AES BA/RARAWAI MILL PENANG MILL MATEI AIRFIELD VANUABALAVU U/S LAKEBA NO OBSERVATION LEVUKA VUNISEA MATUKU ONO-I-LAU MEAN TEMPERATURE IS (MAX+MIN)/2; WIND IS MEAN SPEED AT 6,12,18,24HOURS; $: SOLAR RA- DIATION CALCULATED FROM SUNSHINE DURATION; #: DEPARTURE FROM LONG-TERM AVERAGES (1971-2); +: NUMBER OF DAYS WITH.1 MM OR MORE RAIN; *: PERCENT OF LONG-TERM AVERAGES; U/S: UNSERVICEABLE; MISSING DATA WITH LESS THAN FIVE DAYS. 4

5 Degrees Celsius (⁰C) Millimetres Degrees Celsius (⁰C) Millimetres Degrees Celsius (⁰C) Millimetres Fiji Climate Summary - July 216 Volume 37 : Issue 7 Figure 2 Nadi Airport (Western Division) - Temperature & Rainfall Records for the last 13 Months (July July 216) 34 Total Monthly Rainfall Long Term Average Rainfall (1971-2) Monthly Average Maximum Temperature Long Term Average Max Temp (1971-2) Monthly Average Minimum Temperature Long Term Average Min Temp(1971-2) Jul-15 Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul-16 Figure 3 Laucala Bay - (Suva) (Central Division) - Temperature & Rainfall Records for the last 13 Months (July July 216) 34. Total Monthly Rainfall Long Term Average Rainfall (1971-2) Monthly Average Maximum Temperature Long Term Average Max Temp (1971-2) Monthly Average Minimum Temperature Long Term Average Min Temp (1971-2) Jul-15 Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul-16 Figure 4 Labasa Airport (Northen Division) - Temperature & Rainfall Records for the last 13 Months (July July 216) 34 Total Monthly Rainfall Long Term Average Rainfall (1971-2) Monthly Average Maximum Temperature Long Term Average Max Temp (1971-2) Monthly Average Minimum Temperature Long Term Average Min Temp(1971-2) Jul-15 Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul-16 5

6 Degrees Celsius (⁰C) Millimetres Fiji Climate Summary - July 216 Volume 37 : Issue 7 Figure 5 Lakeba (Eastern Division) - Temperature & Rainfall Records for the last 13 Months (July July 216) 34 Total Monthly Rainfall Long Term Average Rainfall (1971-2) Monthly Average Maximum Temperature Long Term Average Max Temp (1971-2) Monthly Average Minimum Temperature Long Term Average Min Temp (1971-2) Jul-15 Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul RELATIVE HUMIDITY AT 9HOURS The 9am average relative humidity (RH) ranged from 63% to 87% during the month (Table 2). The Western Division stations recorded daily average RH values between 63% and 84%. The most significant negative mean monthly RH anomaly from the normal was observed at Lautoka Mill with 9.2%, while the greatest positive departure was observed at Viwa with +3.6%. The Central Division stations recorded daily average RH values between 77% and 81%. Negative mean monthly RH departures from the normal were recorded across the Division, with the most significant anomaly of 3.9% observed at Koronivia. The stations in the Northern Division registered daily average RH between 71% and 81%. The most significant negative mean monthly RH anomaly from the normal was observed at Matei Airfield with 5.8%, while the greatest positive departure was at Nabouwalu with +1.5%. The mean month RH in the Eastern Division ranged from 71% to 75%. Negative anomalies from the normal were recorded throughout the Division, with the most significant departure of 3.% at Vunisea. The daily average RH at Monasavu was 87%, while it was 81% at Rotuma. 6. SUNSHINE Laucala Bay, Nacocolevu, Nadi Airport and Rotuma recorded 126%, 121%, 11% and 13% of the normal bright sunshine hours during the month, respectively (Table 2). Nadi Airport recorded hours of total bright sunshine, with a mean of 7.8 hours/day. The longest duration of bright sunshine at the station was 1.8 hours on the 3 th, while generally overcast conditions persisted on the 1 st with only.1 hour of bright sunshine. the 24 th. In contrast, overcast conditions persisted on the 1 st, with no bright sunshine recorded. Rotuma recorded 25.1 hours of the total bright sunshine, with a mean of 6.8 hours/day. The longest duration of bright sunshine at the station was 9.4 hours on the 15 th. Note that Rotuma s analysis is presented with 1 day of missing record. Laucala Bay recorded 17.1 hours of total monthly bright sunshine, with a mean of 5.5 hours/day. The longest duration of bright sunshine at the station was 1.5 hours on the 23 rd. On the other hand, overcast conditions persisted from 1 st to 4 th with no bright sunshine recorded. The total monthly bright sunshine at Nacocolevu was 21. hours, with a daily mean of 6.5 hours. The station s highest daily bright sunshine of 9.5 hours was recorded on 6

7 7. WIND SUMMARY The 1-minute average wind statistics recorded every three hours at Nadi Airport in July showed that easterly winds were predominant, accounting for 38.7% of the total observations, followed by westerly with 19.4% and southeasterly with 11.7% (Figure 6(a)). Calm conditions were recorded on 8.1% of the occasions. The 1-minute average wind speeds were light to moderate in strength (Figure 6 (b)). At Nausori Airport, winds from east were dominant, accounting for 22.4% of the records, followed by southeast with 17.8%. Calm conditions accounted for 34.% of the observations (Figure 7(a)). The wind speeds ranged from light to moderate in strength (Figure 7(b)). Incidentally, the wind anomalies map on the NOAA website show persistence of near normal winds in the Fiji region (Figure 13). Note: light air: 1-3 knots, light breeze: 4 6 knots, gentle breeze: 7-1 knots, moderate breeze: knots, fresh breeze: knots, strong breeze: 22-27knots, near gale: knots; gale: 34-4 knots; strong gale: knots Figure 6(a) Surface Wind Direction for Nadi Airport, Fiji. (WMO 9168 Lat 17 45'35"South Long '42"East Height above MSL 22m) Figure 6(b) Surface Wind Speed for Nadi Airport, Fiji. (WMO 9168 Lat 17 45'35"South Long '42"East Height above MSL 22m) SW 4.4% W 19.4% NW 2.4% CALM 8.1% N 2.% NE 1.9% 7-1 knots 25.% [CATEGORY NAME] 9.6% CALM 8.1% 1-3 knots 19.4% S 2.4% SE 11.7% E 38.7% 4-6 knots 37.9% Figure 7(a) Surface Wind Direction for Nausori Airport, Fiji. (WMO Lat 18 2'47"South Long '33"East Height above MSL 3m) Figure 7(b) Surface Wind Speed for Nausori Airport, Fiji. (WMO Lat 18 2'47"South Long '33"East Height above MSL 3m) S 11.3% W SW.4% 4.% NW 6.9% CALM 34.% 7-1 knots 27.5% knots 3.2% CALM 34.% SE 17.8% [CATEGORY NAME] 22.4% N.4% NE 2.8% 4-6 knots 29.6% 1-3 knots 5.7% 7

8 Radiation (MJ/m 2 ) Evaporation (mm) Fiji ` Climate Summary - July 216 Volume 37 : Issue 7 8. EVAPORATION Figure Nadi Laucala Bay, Suva Daily Evaporation for July Days in July The total monthly raised pan evaporation at Nadi Airport was 133.5mm, while Laucala Bay recorded 12.3mm. Nadi Airport s highest daily evaporation was 7.6mm on the 31 st, while Laucala Bay recorded the highest of 6.mm on the 12 th and 17 th. 9. RADIATION Daily Radiation at Nadi Airport during July 216 Figure 9: The mean daily solar radiation at Nadi Airport during July 216 was 14.1MJ/m 2, while the normal during July is 14.7MJ/m Days in July SEA SURFACE TEMPERATURE (SST) Figure 1: SST was near normal in most of the Fiji region (base period: ). psd/map/clim/sst.shtml 8

9 CLOUD COVER Figure 11: OLR anomalies indicate presence of below normal cloud cover in the Fiji region (Fiji: ~17ºS, 18º) (base period: ). psd/map/clim/olr.shtml SEA LEVEL Figure 12: Negative sea level anomalies persisted in the Fiji waters, ranging from 5 to 15cm (base period: ). products/ analysis_monitoring/ ocean/ weeklyenso_clim_81-1/ wksl_anm.gif WIND ANOMALIES Figure 13: Reanalysis data suggest near normal winds persisted in the Fiji region (Fiji: ~17ºS, 18º) (base period: ). psd/map/images/rnl/ sfcwnd_3a.rnl.gif This Summary is prepared as soon as ENSO, climate and oceanographic data is received from recording stations around Fiji and Meteorological Agencies around the World. Delays in data collection, communication and processing occasionally arise. While every effort is made to verify observational data, the Fiji Meteorological Service does not guarantee the accuracy and reliability of the analyses presented, and accepts no liability for any losses incurred through the use of this information and its contents. The information can be freely disseminated provided the source is acknowledged. For further information, contact: The Director of Meteorology, Fiji Meteorological Service, Private Mail Bag NAP351, Nadi Airport, Fiji. Phone: (679) , Fax: (679) 67243, fms@met.gov.fj or climate@met.gov.fj. URL: 9