Number 105, June 2009
The Island
Climate Update
Collaborators
Pacific Islands National
Meteorological Services
Australian Bureau of
Meteorology
Meteo France
NOAA National
Weather Service
NOAA Climate
Prediction Centre
(CPC)
International Research
Institute for Climate
and Society
European Centre
for Medium Range
Weather Forecasts
UK Met Office
World Meteorological
Organization
MetService of
New Zealand
May’s climate
•
The South Pacific Convergence Zone (SPCZ) was positioned
southwest of normal.
•
Suppressed convection near Western Kiribati and along the Equator
extending east through Nauru and Eastern Kiribati.
•
Mostly well above normal rainfall for New Caledonia and many
parts of Fiji.
El Niño/Southern Oscillation (ENSO), seasonal
rainfall, and sea surface temperature forecasts
•
ENSO neutral conditions exist in the tropical Pacific. Most climate
models project ENSO neutral conditions for winter 2009. Some
climate models suggest El Niño could develop early in Austral
spring.
•
Below normal rainfall is forecast for Tuvalu, Tokelau, the Marquesas
and the Northern Cook Islands.
•
Normal or above normal rainfall is expected for Papua New
Guinea, the Solomon Islands, Western Kiribati, Vanuatu, Niue,
Tonga, the Southern Cook Islands, and the Austral Islands.
•
Above normal SSTs are forecast for Papua New Guinea. Normal or
above normal SSTs are forecast for the western half of the southwest
Pacific. Near normal SSTs are expected elsewhere.
The Island Climate Update, No. 105, June 2009
Page 2
Climate developments in May 2009
Outgoing Long-wave Radiation (OLR) anomalies, in Wm
2
are
represented by hatched areas. High radiation levels (yellow) are
typically associated with clearer skies and lower rainfall, while cloudy
conditions lower the OLR (blue) and typically result in higher rainfall.
The May 2009 position of the South Pacific Convergence Zone (SPCZ)
was displaced southwest of its normal position, but weakly coherent
compared to previous months. The average position of the SPCZ is
identified by the dashed green line, which is based on mean January
rainfall for the South Pacific. Mean sea level (MSL) pressure anomalies
(in hPa) are shown as solid and dashed black lines.
-90 -70 -50 -30 -20 -10 10 20 30 50 70 90
Australia
NewZealand
Fiji
NewCaledonia
Vanuatu
Solomon Is
Pitcairn
Samoa
Tonga
Niue
EKiribati
PapuaNewGuinea
NCook Is
S Cook Is
Society Is
WKiribati
Line Is
Tuvalu
Marquesas Is
Austral Is
Marshall Is
Rawaki Is
Tokelau Is
Nauru
Fed States of Micronesia
Tuamotu Is
EQUATOR
Wallis & Futuna
H
L
H
0 -1
+1
-2 -3 -4 -5
-6
-7
Soil moisture in May 2009
Estimated soil moisture conditions at the end of May 2009, using
monthly rainfall data. Soil moisture projections for individual Pacific
Island countries are dependent on data availability at the time of
publication.
E
stimates of soil moisture shown in the map (right) are
based on monthly rainfall for one station in each country.
Currently there are not many sites in the water balance model,
but more stations will be included in the future.
The information displayed is based on a simple water balance
technique to determine soil moisture levels. Addition of
moisture to the available water already in the soil comes
from rainfall, with losses via evapotranspiration. Monthly
rainfall and evapotranspiration are used to determine the
soil moisture level and its changes. These soil moisture
calculations were made at the end of the month, and for
practical purposes, generalisations were made about the
available water capacity of the soils at each site.
Hanan (Niue), Apia (Samoa), Port Vila (Vanuatu), Nadi (Fiji)
and Fua’amotu (Tonga) project moist soil moisture conditions.
Soil moisture is moderate at Rarotonga (Southern Cook
Islands), and dry at Tarawa and Kiritimati (Kiribati).
T
he South Pacific Convergence Zone (SPCZ) was
displaced southwest of its normal position last month,
but exhibited less coherent rainfall concentrations than in
previous months. A region of enhanced rainfall, partly due to
intensified convection, was observed over part of Vanuatu,
New Caledonia, and Fiji during May. Suppressed convection
existed northeast of the Solomon Islands during May, in a
zone including Western Kiribati, Nauru, and to the north
of Tuvalu. There was also suppressed convection along the
equator including Eastern Kiribati, and from the Northern
Cook Islands to the Austral Islands. The regional circulation
in May was characterised by more frequent low pressure
near Pitcairn Island and higher than normal pressure in the
northwestern portion of the southwest Pacific.
High precipitation totals were concentrated in the western
half of the southwest Pacific during May, and also the far east
and south of French Polynesia. Drier than normal conditions
occurred over much of the Society Islands and the Marquesas,
which also experienced more frequent easterly winds than
normal during the month. Nearby in the Southern Cook
Islands, well below normal rainfall occurred at Rarotonga
and Aitutaki (50 and 100mm, respectively). Most stations
in Fiji received well above normal rainfall during May. The
exceptions were Laucala Bay, Lakeba, and Vunisea, which
received well below to below normal rainfall (25 – 75%
of normal). In addition, much drier than normal conditions
occurred in the North Tasman region this past month, with
Norfolk, Raoul, and Lord Howe Islands recording 25 – 30%
of normal rainfall.
There were some localised high rainfall totals in the southwest
Pacific during May, particularly in the northern regions of
New Caledonia and its eastern offshore islands. Koumac
and La Roche received more than 275% normal rainfall, a
contrast to the near normal totals for the southern part of
New Caledonia, and below normal rainfall levels observed
nearby in the North Tasman Sea.
In Tonga, normal or well below normal rainfall was recorded,
with a low of 46mm at Lupepau’u (24% of normal). Monthly
rainfall reports also inidcated drier than normal conditions
occurred in Tuvalu, which had 30 – 90% of normal rainfall
in May. Northern New Zealand had a wetter than normal
month, with 130 – 170% of normal rainfall recorded in the
Wet
Moderate
Dry
Wet
Moderate
Dry
Wet
Moderate
Dry
Wet
Moderate
Dry
May 2009
May 2008
Island Group
Location
Rainfall
(mm)
% of
avg
Comments
Fiji
Nacocolevu
322
379
Record high
Vanuatu
Sola
680
183
Highest monthly
total in the region
North Tasman
Raoul Island
37
30
Record low
North Tasman
Norfolk
Island
37
26
Very low
North Tasman
Lord Howe
Island
48
30
Very low
northern part of the country.
Australia
New Zealand
Fiji
New Caledonia
Vanuatu
Solomon Is
Samoa
Tonga
Niue
E Kiribati
Papua New Guinea
S Cook Is
N Cook Is
Society Is
W Kiribati
Line Is
Tuvalu
Marquesas Is
Austral Is
Marshall Is
Rawaki Is
Tokelau Is
Nauru
Fed. States of
Micronesia
Tuamotu Is
Pitcairn
EQUATOR
July 2008
July 2007
Wet
Moderate
Dry
Wet
Moderate
Dry
The Island Climate Update, No. 105, June 2009
Page 3
Mean sea surface temperatures (ºC) for May 2009
Sea surface temperature anomalies (ºC) for May 2009
Forecast validation: March to May 2009
-3.0
-2.0
-1.0
0.5
1.5
2.5
Australia
New Zealand
Fiji
New Caledonia
Vanuatu
Solomon Is
Samoa
Tonga
Niue
E Kiribati
Papua New Guinea
S Cook Is
N Cook Is
Society Is
W Kiribati
Line Is
Tuvalu
Marquesas Is
Austral Is
Marshall Is
Rawaki Is
Tokelau Is
Nauru
Fed States of Micronesia
Tuamotu Is
Pitcairn
EQUATOR
Wallis & Futuna
10 12 14 16 18 20 22 24 26 28 30 32
Australia
New Zealand
Fiji
New Caledonia
Vanuatu
Solomon Is
Samoa
Tonga
Niue
E Kiribati
Papua New Guinea
S Cook Is
N Cook Is
Society Is
W Kiribati
Line Is
Tuvalu
Marquesas Is
Austral Is
Marshall Is
Rawaki Is
Tokelau Is
Nauru
Fed States of Micronesia
Tuamotu Is
Pitcairn
EQUATOR
Wallis & Futuna
El Niño/Southern Oscillation (ENSO)
D
uring May, the equatorial Pacific Ocean exhibited
ENSO-neutral
characteristics.
Sea
surface
temperatures (SSTs) in that region have been rising
steadily since February, and are now warmer than normal
across the entire Pacific basin. NINO3 and NINO 4 SST
anomalies are +0.8°C and +0.3°C, respectively, for
May (and +0.1°C and –0.0°C, respectively, for MAM).
SSH anomalies still remain positive in the tropical Pacific
west of the Date Line, but show a north-south banded
structure in the east, with positive anomalies along
the Equator east of the Date Line. Positive equatorial
subsurface ocean temperature anomalies strengthened
during May in the uppermost 100m near the South
American coast, and now exceed +3°C. The upper
ocean heat content, averaged over the top 300m, is
positive right across the equatorial Pacific.
Westerly anomalies are now evident in the trade winds
west of the Date Line. The TRMM ENSO precipitation
index remains negative at –1.0, about the only indicator
remaining of the recent La Niña. At the same time, the
SOI fell rapidly to a value of –0.5 in May (but averaged
+0.1 over MAM). Tropical Pacific convection (from
OLR) was enhanced over Indonesia and north of
Australia in late May, but was still suppressed along the
Equator, east of 150°E, MJO activity was heightened
at the end of May and convection was expected to
propagate at least as far as the Date Line during the first
week of June.
The global climate model ensemble assessed by NIWA
show statistical models are signaling ENSO–neutral
conditions into early 2010. However, seven of the 10
dynamical models that are monitored indicate reaching
an El Niño threshold by the end of Austral winter. Thus,
the ENSO discussion has shifted from whether La Niña
will continue through winter to whether current neutral
conditions will transition into El Niño before the end
of the year. Most forecasts still expect Austral winter to
be ENSO–neutral. The Australia Bureau of Meteorology
has noted that signs indicating the possible development
of El Niño have strenghtened in early June. NOAA also
A
region of suppressed convection was forecast for the
central and eastern Southwest Pacific, extending from
Tuvalu southeast to the Northern Cook Islands, including
Tokelau, with an expectation of below normal rainfall.
Near–to–below normal rainfall was expected for Samoa,
Eastern Kiribati, and Western Kiribati. Enhanced convection
was expected to extend southeast from Papua New Guinea,
and include New Caledonia, Vanuatu, Tonga, the Southern
Cook Islands and the Austral Islands, where above normal
rainfall was forecast. Near or above normal rainfall was
forecast for Fiji and Niue. Normal rainfall was anticipated for
the Marquesas, Pitcairn Island, and also the Society Islands.
No clear precipitation guidance was offered for the Solomon
Islands, Tuamotu, or Wallis & Futuna for the forecast period.
The March – May 2009 forecast validation was calculated for
13 island groups (four countries did not report rainfall values;
three were forecast as climatology and were unscorable).
The global island group ‘hit’ rate was 64%, 1% higher than
average, and 3% higher than the average for all months
combined. Rainfall was overprojected for Vanuatu, Tonga
and Samoa.
indicates conditions are ripe for El Niño development if the
atmospheric response catches up to the ocean anomalies. The
IRI indicates a 48% chance of neutral ENSO conditions for the
coming season, and a 45% chance of an El Niño.
Tropical Cyclone Activity Summary
E
ight tropical cyclones occurred in the Southwest Pacific during the 2008–09 season, which was one less than the long
term average (1969/70-2007/08). This year was the most active TC season since 2005/06. ICU tropical cyclone guidance
produced in October 2008 projected average TC activity (8–10 TC’s) for the 2008/09 season. The first tropical cyclone
formed on January 28, making this the latest start to the Southwest Pacific TC season since 2000/01. Four TC’s developed
west of the Date Line and five formed east of the Date Line. Peak activity occurred in March (four TC’s), and December and
February were unusually quiet, and only one TC reached hurricane intensity (sustained wind speeds of at least 118 km).
The Island Climate Update, No. 105, June 2009
Page 4
Tropical Pacific rainfall – May 2009
Rainfall totalling 200% or more is considered well above average. Totals of 40% or less are normally well below average. Highlighted values are
new records.
Data are published as received and may be subject to change after undergoing quality control checks. N/A denotes data unavailability at the time
of publishing, and * denotes synoptic values.
Territory and
station station
name
May 2009
rainfall
total (mm)
May 2009
percent of
average
Australia
Cairns Airport
89
93
Townsville Airport
7
19
Brisbane Airport
241
243
Sydney Airport
126
130
Cook Islands
Penrhyn
N/A
N/A
Aitutaki
100
51
Rarotonga Airport
50
30
Fiji
Rotuma Island
279
94
Udu Point
241
144
Nadi Airport
163
183
Nausori
308
124
French Polynesia
Hiva Hoa, Atuona
104
66
Bora Bora
99
89
Tahiti – Faa’a
34
33
Tuamotu, Takaroa
96
109
Gambier, Rikitea
237
172
Tubuai
126
75
Rapa
305
137
Kiribati
Tarawa
166
86
Kanton
50
40
New Zealand
Kaitaia
157
132
Whangarei Airport
139
129
Auckland Airport
151
164
New Caledonia
Ile Art, Belep
275
133
Koumac
175
287
Ouloup
169
159
Ouanaham
237
174
Poindimie
237
117
La Roche
386
278
La Tontouta
83
148
Noumea
88
102
Moue
101
78
Territory and
station station
name
May 2009
rainfall
total (mm)
May 2009
percent of
average
Niue
Hanan Airport
160
110
Liku
164
98
North Tasman
Lord Howe Island
48
30
Norfolk Island
37
26
Raoul Island
37
30
Samoa
Faleolo Airport
258
163
Apia
173
99
Nafanua
198
N/A
Afiamalu
233
N/A
Maota
235
N/A
Solomon Islands
Taro
306
113
Munda
362
150
Auki
171
86
Honiara
165
116
Henderson
111
84
Kira Kira
348
114
Santa Cruz, Lata
303
85
Tonga
Niuafo’ou
325
196
Mata’aho Airport
130
78
Lupepau’u
46
24
Salote Airport
67
39
Nuku’alofa
102
92
Fua’amotu Airport
181
134
Tuvalu
Nanumea
73
32
Nui Island
209
95
Funafuti
119
48
Nuilakita
202
86
Vanuatu
Sola
680
183
Pekoa
388
181
Lamap
75
45
Port Vila
109
75
Tanna/Whitegrass
105
N/A
Aneityum
258
166
The Island Climate Update, No. 105, June 2009
Page 5
Rainfall outlook map for June to August 2009
Tropical rainfall and SST outlook: June to August 2009
NOTE: Rainfall and sea surface termperature estimates for Pacific Islands for the next three months are given in the tables below. The tercile probabilities (e.g.,
20:30:50) are derived from the averages of several global climate models. They correspond to the odds of the observed rainfall or sea surface temperatures being in
the lowest one third of the distribution, the middle one third, or the highest one third of the distribution. For the long term average, it is equally likely (33% chance)
that conditions in any of the three terciles will occur. *If conditions are climatology, we expect an equal chance of the rainfall being in any tercile.
D
uring June – August 2009, a region of suppressed
convection is likely in the southwest Pacific
encompassing Tokelau, Tuvalu, the Northern Cook Islands,
and the Marquesas, with below average rainfall expected
for those areas. Near normal rainfall is forecast for Pitcairn
Island and the Tuamotu Archipelago. Enhanced convection
is likely around Papua New Guinea, the Solomon Islands,
Western Kiribati, Vanuatu, Niue, Tonga, the Southern Cook
Islands, and the Austral Islands with average or above
average rainfall anticipated for the coming three month
period. No clear precipitation guidance is offered for Fiji,
New Caledonia, Eastern Kiribati, Samoa, the Society Islands,
or Wallis & Futuna.
Prominent negative equatorial SST anomalies that existed
in the region during the past months have eased. Global
models indicate significant shifts to near-neutral SSTs during
Austral winter, and a subsequent swing toward warm
anomalies as early as Austral spring. Above average SSTs
are expected for Papua New Guinea, while near or above
average SSTs are forecast for Western Kiribati, the Solomon
Islands, Vanuatu, Fiji, the Southern Cook Islands, and the
Austral Islands. Near normal SSTs are forecast for Samoa,
Tokelau, Tuvalu, the Northern Cook Islands, Wallis &
Futuna, Tonga, the Marquesas, Eastern Kiribati, the Tuamotu
Archipelago, Pitcairn Island, and the Society Islands. No
clear SST guidance is provided for New Caledonia or Niue.
The confidence in the multi-model ensemble forecast skill
for this seasonal rainfall outlook is moderately high for most
Pacific Island countries. In the past, the average region-
wide hit rate for rainfall forecasts issued in June is 60%, 1%
lower than the long-term average for all months combined.
The SST forecast confidence is moderate–to–high for this
period.
Island Group
Rainfall Outlook
Outlook confidence
Cook Islands (Southern)
25:35:40 (Near or Above)
Moderate-High
Kiribati (Western)
25:35:40 (Near or Above)
Moderate
Niue
25:35:40 (Near or Above)
Moderate-High
Papua New Guinea
25:35:40 (Near or Above)
Moderate-High
Solomon Islands
25:35:40 (Near or Above)
Moderate
Tonga
25:35:40 (Near or Above)
Moderate-High
Vanuatu
25:35:40 (Near or Above)
Moderate-High
Austral Islands
25:35:40 (Near or Above)
Moderate
Pitcairn Island
30:40:30 (Near normal)
Moderate
Tuamotu Islands
30:40:30 (Near normal)
Moderate
Fiji
30:35:35 (Climatology)
Moderate
New Caledonia
30:35:35 (Climatology)
Moderate
Kiribati (Eastern)
35:35:30 (Climatology)
Moderate
Samoa
35:35:30 (Climatology)
Moderate
Society Islands
35:35:30 (Climatology)
Moderate
Wallis & Futuna
35:35:30 (Climatology)
Moderate
Marquesas
45:35:20 (Below)
Moderate-High
Cook Islands (Northern)
45:35:20 (Below)
Moderate-High
Tokelau
45:35:20 (Below)
Moderate-High
Tuvalu
45:35:20 (Below)
Moderate-High
Australia
New Zealand
Fiji
New Caledonia
Vanuatu
Solomon Is
Pitcairn
Samoa
Tonga
Niue
E Kiribati
Papua New Guinea
N Cook Is
S Cook Is
Society Is
W Kiribati
Line Is
Tuvalu
Marquesas Is
Austral Is
Marshall Is
Rawaki Is
Tokelau Is
Nauru
Fed States of Micronesia
Tuamotu Is
EQUATOR
Wallis & Futuna
NO
FORECAST
SST outlook map for June to August 2009
Island Group
SST Outlook
Outlook confidence
Papua New Guinea
20:35:45 (Above)
Moderate
Austral Islands
25:35:40 (Near or Above)
Moderate-High
Cook Islands (Southern)
25:35:40 (Near or Above)
Moderate-High
Fiji
25:35:40 (Near or Above)
Moderate-High
Solomon Islands
25:35:40 (Near or Above)
Moderate-High
Vanuatu
25:35:40 (Near or Above)
Moderate-High
Kiribati (Western)
25:40:35 (Near or Above)
Moderate-High
New Caledonia
30:35:35 (Climatology)
Moderate
Niue
30:35:35 (Climatology)
Moderate
Cook Islands (Northern)
30:40:30 (Near normal)
High
Kiribati (Eastern)
30:40:30 (Near normal)
Moderate
Marquesas
30:40:30 (Near normal)
Moderate
Pitcairn Island
30:40:30 (Near normal)
High
Samoa
30:40:30 (Near normal)
High
Society Islands
30:40:30 (Near normal)
High
Tokelau
30:40:30 (Near normal)
High
Tonga
30:40:30 (Near normal)
High
Tuamotu Islands
30:40:30 (Near normal)
High
Tuvalu
30:40:30 (Near normal)
High
Wallis & Futuna
30:40:30 (Near normal)
High
Australia
New Zealand
Fiji
New Caledonia
Vanuatu
Solomon Is
Pitcairn
Samoa
Tonga
Niue
E Kiribati
Papua New Guinea
N Cook Is
S Cook Is
Society Is
W Kiribati
Line Is
Tuvalu
Marquesas Is
Austral Is
Marshall Is
Rawaki Is
Tokelau Is
Nauru
Fed States of Micronesia
Tuamotu Is
EQUATOR
Wallis & Futuna
BELOW
NEAR OR
BELOW
NEAR
NORMAL
NEAR OR
ABOVE
ABOVE
The Island Climate Update, No. 105, June 2009
Page 6
Sources of South Pacific rainfall data
This bulletin is a multi-national project,
with important collaboration from the
following
Meteorological
Services:
American Samoa, Australia, Cook
Islands, Fiji, French Polynesia, Kiribati,
New Caledonia, New Zealand, Niue,
Papua New Guinea, Pitcairn Island,
Samoa, Solomon Islands, Tokelau,
Tonga, Tuvalu, Vanuatu, Wallis and
Futuna.
Web links to ICU partners:
South Pacific Meteorological Services:
Cook Islands
http://www.cookislands.pacificweather.org/
Fiji
http://www.met.gov.fj
Kiribati
http://pi-gcos.org/index.php (follow link to PI Met
Services then Kiribati Met Service)
New Zealand
http://www.metservice.co.nz/
Niue
http://pi-gcos.org/index.php (follow link to to PI Met
Services then Niue Met Service)
Papua New Guinea
http://pi-gcos.org/index.php (follow link to to PI Met
Services then Papua New Guinea Met Service)
Samoa
http://www.mnre.gov.ws/meteorology/
Solomon Islands
http://www.met.gov.sb/
Tonga
http://www.met.gov.to/
Tuvalu
http://tuvalu.pacificweather.org/
Vanuatu
http://www.meteo.gov.vu/
International Partners
Meteo-France
New Caledonia: http://www.meteo.nc/
French Polynesia: http://www.meteo.pf/
Bureau of Meteorology (Australia)
http://www.bom.gov.au/
National Oceanographic and Atmospheric Administration
(USA)
National Weather Service: http://www.nws.noaa.gov/
Climate Prediction Center: http://www.cpc.noaa.gov/
The International Research Institute for Climate and
Society (USA):
http://portal.iri.columbia.edu/portal/server.pt
The UK Met Office
http://www.metoffice.gov.uk/
European Centre for Medium-term Weather Forecasts
http://www.ecmwf.int/
Cover Photo:
Wendy St George,
NIWA
Visit The Island Climate Update at:
www.niwascience.co.nz/ncc/icu
Your comments and ideas about The Island
Climate
Update are welcome. Please contact:
Dr Andrew Lorrey, NIWA,
41 Market Place, Auckland, New Zealand
E-mail:
a.lorrey@niwa.co.nz
Forecasts:
Dr. Andrew Lorrey (South Pacific rainfall
and SST forecasts) and the NIWA National
Climate Centre (ENSO wrap)
ICU Editors:
Andrew Lorrey Email:
a.lorrey@niwa.co.nz
James Renwick Email:
j.renwick@niwa.co.nz
Harriet Palmer Email:
h.palmer@niwa.co.nz
Acknowledgements
This bulletin is produced by NIWA and
made possible with financial support from
the New Zealand Agency for International
Development (NZAID), with additional
support from the Pacific Islands Applied
Geosciences Commission (SOPAC) and
the Secretariat for the Pacific Regional
Environmental
Programme
(SPREP).
This summary is prepared as soon as possible
following the end of the month, once the
data and information are received from
the Pacific Island National Meteorological
Services (NMHS). Delays in data collection
and communication occasionally arise. While
every effort is made to verify observational
data, NIWA does not guarantee the accuracy
and reliability of the analysis and forecast
information presented, and accepts no
liability for any losses incurred through
the use of this bulletin and its content.
The contents of The Island Climate
Update may be freely disseminated,
provided the source is acknowledged.
Requests for Pacific Island climate data
should be directed to the Meteorological
Services concerned.
The Island
Climate Update