Climate Outlook April-June '10: Warm end to Autumn
NIWA NATIONAL CLIMATE CENTRE / 31 March 2010
SEASONAL CLIMATE OUTLOOK:
April – June 2010
A warm end to Autumn
The NIWA National Climate Centre says that mean temperatures are very likely to be above the long-term average in most parts of the country, over the three months April–June. However, short-term cold snaps will still occur, especially as we move into winter. Despite recent dryness, near normal seasonal rainfalls are likely in most places.
The centre’s latest outlook, for late autumn 2010, states that mean sea level pressures are likely to be slightly lower than normal over the country, associated with slightly stronger than normal westerlies over New Zealand, on average for April-June. The current El Niño in the equatorial Pacific is expected to weaken to neutral conditions by the winter.
Below normal soil moisture levels and stream flows are expected for the April–June period in the north and east of the North Island, and in the east of the South Island. Near normal or below normal soil moisture levels and streamflows are likely in most other regions.
Overall
Picture
Temperature:
Above average temperatures are very likely across the country, over the three months of April to June as a whole. Sea surface temperatures are expected to be above average around the coasts.
Rainfall,
soil moisture, and stream flows:
Rainfall is likely to be near normal in most regions, but near normal or below normal in the eastern South Island. Below normal soil moisture levels and stream flows are expected for the April–June period in the north and east of the North Island, and in the east of the South Island. Near normal soil moisture levels and streamflows are likely for the south and west of the South Island. Elsewhere, soil moisture levels and streamflows are equally likely to be in the near normal or below normal range.
Regional predictions for the next three
months:
Northland, Auckland, Waikato,
Bay of Plenty:
Temperatures are very likely to be above average. Seasonal rainfall totals are likely to be near normal, while below normal soil moisture levels are likely. Stream flows are very likely to be in the below normal range.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
/ Temperature /
Rainfall / Soil moisture / Stream flows
Above average / 60% / 20% / 20% / 10%
Near average / 30% / 50% / 30% / 30%
Below average / 10% / 30% / 50% / 60%
Central North Island, Taranaki, Wanganui,
Manawatu and Wellington:
Above average seasonal temperatures are very likely. Rainfall totals are likely to be near normal, while stream flows and soil moisture levels are equally likely to be in the near normal or below normal range, for the three months as a whole.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
/ Temperature / Rainfall / Soil moisture / Stream
flows
Above average / 60% / 25% / 20% / 20%
Near average / 30% / 50% / 40% / 40%
Below average / 10% / 25% / 40% / 40%
Gisborne, Hawke’s Bay, Wairarapa:
Temperatures averaged over the three months are very likely to be in the above average category. Seasonal rainfall totals are predicted to be near normal, but stream flows and soil moisture levels are likely to be in the below normal range.
Probabilities are assigned in three categories; above normal, near normal, and below normal. The full probability breakdown is:
/ Temperature / Rainfall / Soil moisture / Stream
flows
Above average / 60% / 20% / 10% / 10%
Near average / 30% / 50% / 40% / 40%
Below average / 10% / 30% / 50% / 50%
Nelson, Marlborough,
Buller:
Seasonal temperatures are likely to be in the above average range. Rainfalls are likely to be near normal overall, while stream flows and soil moisture levels are equally likely to be near normal or below normal.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
/ Temperature / Rainfall /
Soil moisture / Stream flows
Above average / 50% / 30% / 20% / 20%
Near average / 30% / 50% / 40% / 40%
Below average / 20% / 20% / 40% / 40%
West Coast,
Alps and Foothills, Inland Otago,
Southland:
Temperatures are very likely to be in the above average category. Seasonal rainfall, stream flows and soil moisture levels are likely to be near normal.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
/ Temperature / Rainfall /
Soil moisture / Stream flows
Above average / 60% / 30% / 30% / 30%
Near average / 30% / 50% / 50% / 50%
Below average / 10% / 20% / 20% / 20%
Coastal
Canterbury, East Otago:
Temperatures are very likely to be in the above average category, on the whole during April–June. Seasonal rainfall totals are equally likely to be in the normal or the below normal range, while soil moisture levels and stream flows are very likely to be below normal.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
/ Temperature /
Rainfall / Soil moisture / Stream flows
Above average / 60% / 20% / 10% / 10%
Near average / 30% / 40% / 30% / 30%
Below average / 10% / 40% / 60% / 60%
Background
An El Niño
continues in the Tropical Pacific, but is showing signs of
weakening, and neutral conditions are expected by the
winter.
--
© Copyright NIWA 2010. All rights reserved. Acknowledgement of NIWA as the source is required.
Notes to reporters & editors
1. NIWA’s outlooks indicate the
likelihood of climate conditions being at, above, or below
average for the season as a whole. They are not ‘weather
forecasts’. It is not possible to forecast precise weather
conditions three months ahead of time.
2. The outlooks
are the result of the expert judgment of NIWA’s climate
scientists. They take into account observations of
atmospheric and ocean conditions and output from global and
local climate models. The presence of El Niño or La Niña
conditions and the sea surface temperatures around New
Zealand can be a useful indicator of likely overall climate
conditions for a season.
3. The outlooks state the
probability for above average conditions, near average
conditions, and below average conditions for rainfall,
temperature, soil moisture, and stream flows. For example,
for winter (June-July-August) 2007, for all the North
Island, we assigned the following probabilities for
temperature:
• Above average: 60%
• Near average: 30%
• Below average: 10%
We therefore concluded that above average temperatures were very likely.
4. This
three-way probability means that a random choice would only
be correct 33% (or one-third) of the time. It would be like
randomly throwing a dart at a board divided into 3 equal
parts, or throwing a dice with three numbers on it. An
analogy with coin tossing (a two-way probability) is not
correct.
5. A 50% ‘hit rate’ is substantially
better than guess-work, and comparable with the skill level
of the best overseas climate outlooks. See, for example,
analysis of global outlooks issued by the International
Research Institute for Climate and Society based in the U.S.
(http://iri.ldeo.columbia.edu/) published in the Bulletin of
the American Meteorological Society (Goddard, L., A. G.
Barnston, and S. J. Mason, 2003: Evaluation of the IRI's
“net assessment” seasonal climate forecasts 1997-2001.
Bull. Amer. Meteor. Soc., 84,
1761-1781).
6. Each month NIWA publishes an analysis
of how well its outlooks perform. This is available on-line
and is sent to about 3,500 recipients of NIWA’s
newsletters, including many farmers. See The Climate Update:
www.niwascience.co.nz/ncc
7. All outlooks are for the
three months as a whole. There will inevitably be wet and
dry days, hot and cold days, within a season. The exact
range in temperature and rainfall within each of the three
categories varies with location and season. However, as a
guide, the “near average” or middle category for the
temperature predictions includes deviations up to ±0.5°C
from the long-term mean, whereas for rainfall the “near
normal” category lies approximately between 80% and 115%
of the long-term mean.
8. The seasonal climate
outlooks are an output of a scientific research programme,
supplemented by NIWA’s Capability Funding. NIWA does not
have a government contract to produce these
outlooks.
NIWA NATIONAL CLIMATE CENTRE / 31 March 2010
SEASONAL CLIMATE OUTLOOK: /
April – June 2010
A warm end to Autumn
The NIWA National Climate Centre says that mean temperatures are very likely to be above the long-term average in most parts of the country, over the three months April–June. However, short-term cold snaps will still occur, especially as we move into winter. Despite recent dryness, near normal seasonal rainfalls are likely in most places.
The centre’s latest outlook, for late autumn 2010, states that mean sea level pressures are likely to be slightly lower than normal over the country, associated with slightly stronger than normal westerlies over New Zealand, on average for April-June. The current El Niño in the equatorial Pacific is expected to weaken to neutral conditions by the winter.
Below normal soil moisture levels and stream flows are expected for the April–June period in the north and east of the North Island, and in the east of the South Island. Near normal or below normal soil moisture levels and streamflows are likely in most other regions.
Overall
Picture
Temperature:
Above average temperatures are very likely across the country, over the three months of April to June as a whole. Sea surface temperatures are expected to be above average around the coasts.
Rainfall,
soil moisture, and stream flows:
Rainfall is likely to be near normal in most regions, but near normal or below normal in the eastern South Island. Below normal soil moisture levels and stream flows are expected for the April–June period in the north and east of the North Island, and in the east of the South Island. Near normal soil moisture levels and streamflows are likely for the south and west of the South Island. Elsewhere, soil moisture levels and streamflows are equally likely to be in the near normal or below normal range.
Regional predictions for the next three
months:
Northland, Auckland, Waikato,
Bay of Plenty:
Temperatures are very likely to be above average. Seasonal rainfall totals are likely to be near normal, while below normal soil moisture levels are likely. Stream flows are very likely to be in the below normal range.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
/ Temperature /
Rainfall / Soil moisture / Stream flows
Above average / 60% / 20% / 20% / 10%
Near average / 30% / 50% / 30% / 30%
Below average / 10% / 30% / 50% / 60%
Central North Island, Taranaki, Wanganui,
Manawatu and Wellington:
Above average seasonal temperatures are very likely. Rainfall totals are likely to be near normal, while stream flows and soil moisture levels are equally likely to be in the near normal or below normal range, for the three months as a whole.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
/ Temperature / Rainfall / Soil moisture / Stream
flows
Above average / 60% / 25% / 20% / 20%
Near average / 30% / 50% / 40% / 40%
Below average / 10% / 25% / 40% / 40%
Gisborne, Hawke’s Bay, Wairarapa:
Temperatures averaged over the three months are very likely to be in the above average category. Seasonal rainfall totals are predicted to be near normal, but stream flows and soil moisture levels are likely to be in the below normal range.
Probabilities are assigned in three categories; above normal, near normal, and below normal. The full probability breakdown is:
/ Temperature / Rainfall / Soil moisture / Stream
flows
Above average / 60% / 20% / 10% / 10%
Near average / 30% / 50% / 40% / 40%
Below average / 10% / 30% / 50% / 50%
Nelson, Marlborough,
Buller:
Seasonal temperatures are likely to be in the above average range. Rainfalls are likely to be near normal overall, while stream flows and soil moisture levels are equally likely to be near normal or below normal.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
/ Temperature / Rainfall /
Soil moisture / Stream flows
Above average / 50% / 30% / 20% / 20%
Near average / 30% / 50% / 40% / 40%
Below average / 20% / 20% / 40% / 40%
West Coast,
Alps and Foothills, Inland Otago,
Southland:
Temperatures are very likely to be in the above average category. Seasonal rainfall, stream flows and soil moisture levels are likely to be near normal.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
/ Temperature / Rainfall /
Soil moisture / Stream flows
Above average / 60% / 30% / 30% / 30%
Near average / 30% / 50% / 50% / 50%
Below average / 10% / 20% / 20% / 20%
Coastal
Canterbury, East Otago:
Temperatures are very likely to be in the above average category, on the whole during April–June. Seasonal rainfall totals are equally likely to be in the normal or the below normal range, while soil moisture levels and stream flows are very likely to be below normal.
Probabilities are assigned in three categories; above average, near average, and below average. The full probability breakdown is:
/ Temperature /
Rainfall / Soil moisture / Stream flows
Above average / 60% / 20% / 10% / 10%
Near average / 30% / 40% / 30% / 30%
Below average / 10% / 40% / 60% / 60%
Background
An El Niño
continues in the Tropical Pacific, but is showing signs of
weakening, and neutral conditions are expected by the
winter.
--
© Copyright NIWA 2010. All rights reserved. Acknowledgement of NIWA as the source is required.
Notes to reporters & editors
1. NIWA’s outlooks indicate the
likelihood of climate conditions being at, above, or below
average for the season as a whole. They are not ‘weather
forecasts’. It is not possible to forecast precise weather
conditions three months ahead of time.
2. The outlooks
are the result of the expert judgment of NIWA’s climate
scientists. They take into account observations of
atmospheric and ocean conditions and output from global and
local climate models. The presence of El Niño or La Niña
conditions and the sea surface temperatures around New
Zealand can be a useful indicator of likely overall climate
conditions for a season.
3. The outlooks state the
probability for above average conditions, near average
conditions, and below average conditions for rainfall,
temperature, soil moisture, and stream flows. For example,
for winter (June-July-August) 2007, for all the North
Island, we assigned the following probabilities for
temperature:
• Above average: 60%
• Near average: 30%
• Below average: 10%
We therefore concluded that above average temperatures were very likely.
4. This
three-way probability means that a random choice would only
be correct 33% (or one-third) of the time. It would be like
randomly throwing a dart at a board divided into 3 equal
parts, or throwing a dice with three numbers on it. An
analogy with coin tossing (a two-way probability) is not
correct.
5. A 50% ‘hit rate’ is substantially
better than guess-work, and comparable with the skill level
of the best overseas climate outlooks. See, for example,
analysis of global outlooks issued by the International
Research Institute for Climate and Society based in the U.S.
(http://iri.ldeo.columbia.edu/) published in the Bulletin of
the American Meteorological Society (Goddard, L., A. G.
Barnston, and S. J. Mason, 2003: Evaluation of the IRI's
“net assessment” seasonal climate forecasts 1997-2001.
Bull. Amer. Meteor. Soc., 84,
1761-1781).
6. Each month NIWA publishes an analysis
of how well its outlooks perform. This is available on-line
and is sent to about 3,500 recipients of NIWA’s
newsletters, including many farmers. See The Climate Update:
www.niwascience.co.nz/ncc
7. All outlooks are for the
three months as a whole. There will inevitably be wet and
dry days, hot and cold days, within a season. The exact
range in temperature and rainfall within each of the three
categories varies with location and season. However, as a
guide, the “near average” or middle category for the
temperature predictions includes deviations up to ±0.5°C
from the long-term mean, whereas for rainfall the “near
normal” category lies approximately between 80% and 115%
of the long-term mean.
8. The seasonal climate
outlooks are an output of a scientific research programme,
supplemented by NIWA’s Capability Funding. NIWA does not
have a government contract to produce these
outlooks.