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Scoop
5 days ago
- Climate
- Scoop
NIWA Releases Seasonal Climate Outlook – June To August 2025
Press Release – NIWA Rainfall totals during the three months ahead are expected to be above normal for the north of the North Island and near normal for the east of the South Island. For all remaining regions of the country, rainfall is forecast to be near normal or above … Air temperatures are expected to be above average across all New Zealand regions for this winter season, according to NIWA's Seasonal Climate Outlook for June – August 2025. While cold snaps and frost will occur, they are expected to be less frequent than usual, says NIWA Principal Scientist Chris Brandolino. Rainfall totals during the three months ahead are expected to be above normal for the north of the North Island and near normal for the east of the South Island. For all remaining regions of the country, rainfall is forecast to be near normal or above normal. Higher than normal atmospheric pressure is expected to the east of the country, leading to north-easterly flow anomalies that may shift to a more north-westerly direction towards the end of the three-month period. Low pressure systems forming north of the country are still expected to affect New Zealand and may lead to heightened risks for heavy rainfall events. Outlook Summary Neutral El Niño – Southern Oscillation (ENSO) conditions remain present in the tropical Pacific. Residual signals indicative of weak La Niña conditions persist, and occasional La Niña-like atmospheric patterns may still emerge over the next three months International guidance indicates about a 70% chance for the tropical Pacific to remain in an ENSO-neutral state over the outlook period. For New Zealand, higher than normal atmospheric pressure is expected to the east of the country, leading to north-easterly flow anomalies that may shift to a more north-westerly direction towards the end of the three-month period. Low pressure systems forming north of the country are still expected to affect New Zealand and may lead to heightened risks for heavy rainfall events. Seasonal air temperatures are expected to be above average across all New Zealand regions for this winter season. Thus, while cold snaps and frost will occur, they are expected to be less frequent than usual. Sea surface temperatures (SSTs) remain well above average around most of New Zealand, except in offshore areas east of the North Island. In May, coastal SST anomalies ranged from +0.39°C to +1.47°C. Large regions offshore are currently experiencing Marine Heatwave (MHW) conditions. Global climate models suggest that SSTs in the New Zealand region are likely to stay above average over the next three months, although the intensity of the anomalies may ease. Monitor the SST update for updates. June – August rainfall totals are expected to be above normal for the north of the North Island and near normal for the east of the South Island. For all remaining regions of the country, rainfall is forecast to be near normal or above normal. Sub-seasonal, or monthly, projections of rainfall and dryness are updated daily through the NIWA35 forecast. During June – August 2025, near normal soil moisture levels and river flows are expected for all regions of the North Island, while near normal or above normal soil moisture levels and river flows are forecast for the South Island. Regional predictions for June – August 2025 The tables below show the probabilities (or percent chances) for each of three categories: above average, near average, and below average. In the absence of any forecast guidance there would be an equal likelihood (33% chance) of the outcome for any of the three categories. Forecast information from local and global guidance models is used to indicate the deviation from equal chance that is expected for the coming three-month period. All outlooks are for the three months averaged as a whole. During these three months, there will inevitably be relatively wet and dry periods, as well as hot and cold periods. 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 relative to the long-term mean, whereas for rainfall the 'near normal' category lies between 80 percent and 120 percent of the long-term (1991-2020) mean. Northland, Auckland, Waikato, Bay of Plenty Temperatures are very likely to be above average (65% chance). Rainfall totals are most likely to be above normal (45% chance) for June – August 2025 as a whole, with occasional heavy rain events expected. Soil moisture levels and river flows are most likely (45-50% chance) to be near normal Central North Island, Taranaki, Whanganui, Manawatu, Wellington Probabilities are assigned in three categories: above average, near average, and below average. Temperatures are very likely to be above average (60% chance). Rainfall totals are about equally likely to be above normal (40% chance) or near normal (35% chance). Soil moisture levels and river flows are most likely (40-45% chance) to be near normal. Probabilities are assigned in three categories: above average, near average, and below average. Temperatures are most likely to be above average (45% chance). Rainfall totals are about equally likely to be near normal (40% chance) or above normal (35% chance). Soil moisture levels and river flows are most likely (45% chance) to be near normal. Tasman, Nelson, Marlborough, Buller Probabilities are assigned in three categories: above average, near average, and below average. Temperatures are very likely to be above average (60% chance). Rainfall totals are equally likely to be above normal (40% chance) or near normal (35% chance). Soil moisture levels and river flows are equally likely to be near normal (40% chance) or above normal (40% chance). West Coast, Southern Alps and foothills, inland Otago, Southland Probabilities are assigned in three categories: above average, near average, and below average. Temperatures are very likely to be above average (60% chance). Rainfall totals are about equally likely to be near normal (40% chance) or above normal (35% chance). Soil moisture levels and river flows are about equally likely to be near normal (40% chance) or above normal (35% chance). Coastal Canterbury and the nearby plains, east Otago Probabilities are assigned in three categories: above average, near average, and below average. Temperatures are very likely to be above average (60% chance). Rainfall totals are most likely to be in the near normal range (40% chance). Soil moisture levels and river flows are about equally likely to be near normal (40-45% chance) or above normal (35-40% chance). The full probability breakdown is: Graphical representation of the regional probabilities Background Sea surface temperatures (SSTs) anomalies in the central equatorial Pacific (Niño 3.4 Index) in May (values estimated using data to 26 May) are in the ENSO-Neutral range (-0.08C). SSTs currently are slightly below average in parts of the central Pacific, and cooler than average surface waters have re-emerged along the Equator east of about 120oW. The warmer than average ocean waters previously observed off the South American coast have dissipated. The relative Niño 3.4 Index (RONI*) for the past 30 days (to 26 May) was -0.47C, placing it on the La Niña side of neutral, indicating that ocean temperatures in the central and eastern Pacific remain cooler than the tropical average. As of 26 May 2025, the preliminary Southern Oscillation Index (SOI) value for May is +0.68, indicating conditions on the La Niña side of neutral. Atmospheric indicators – such as enhanced trade winds (positive zonal wind anomalies) and stronger-than-normal convective activity over the Maritime Continent – continue to reflect lingering influences from the previous La Niña event. In May 2025, upper-ocean heat content (temperature anomalies in the upper 300 metres of the ocean) remained above average across the western tropical Pacific, particularly west of approximately 170°W. Anomalies exceeding +2°C persisted south of the Equator, from the Maritime Continent to the International Dateline, near the latitude of the Solomon Islands. East of the Dateline, while isolated areas north and south of the Equator exhibited negative anomalies, heat content along the Equator itself was generally near average. This distribution is consistent with the tropical Pacific Ocean having transitioned away from La Niña conditions. In the subsurface equatorial Pacific, ocean temperatures remained significantly above average (anomalies > +3°C) between approximately 100- and 200-metres depth west of 170°W. Over the past week, these warm anomalies have expanded eastward and risen in the water column, with above-average temperatures now observed below roughly 50 metres depth west of about 130°W. In contrast, the central and eastern Pacific show limited cooler anomalies, with only a single isolated pocket of below-average temperatures near 50 metres depth off the South American coast. Taken together, these indicators suggest that the tropical Pacific ocean has largely transitioned away from La Niña conditions observed earlier this year. Notably, the previously prominent east–west gradient in heat content and subsurface temperature anomalies has diminished. Based on the dynamical and statistical models monitored by NIWA, ENSO-Neutral conditions remain the most likely outcome (73% chance) over the next three-month period (June – August 2025). However, intermittent weak La Niña-like atmospheric patterns may still occur over the winter season. For the remainder of the calendar year, ENSO-Neutral conditions are expected to persist. The guidance available however suggests the possibility for La Niña conditions to return by summer 2025 – 2026. The Southern Annular Mode (SAM) was mostly positive during the month of May (85% of days positive) and the monthly average anomaly was +0.5 std. A positive SAM index is typically associated with higher pressure than normal over New Zealand. Over the next two weeks, the SAM is forecast to become temporarily negative and then return to slightly positive values. The Indian Ocean Dipole (IOD) is currently in the neutral range, with the average anomaly for the month of May* 2025 being +0.36oC. The guidance from the Australian Bureau of Meteorology is for the IOD to remain in the neutral range until at least July after which it is forecast to become negative. During May 2025, intra-seasonal convective activity associated with the Madden-Julian-Oscillation (MJO) was generally weak, despite a temporary increase in MJO amplitude over the Maritime Continent mid-May. The MJO is likely to remain weak or indiscernible in the coming two-week period. Sea surface temperatures (SSTs) remain significantly higher than average around much of New Zealand. The exception is off the east coast of the North Island, where SSTs are currently near average. Marine Heatwave (MHW) conditions – defined as five or more consecutive days with SSTs above the 90th percentile – are ongoing along the west and southeast coasts of the South Island, as well as the west and northeast coasts of the North Island. SST forecasts for the June – August 2025 period suggest a slight weakening of these anomalies. However, above-average ocean temperatures are expected to persist around New Zealand through the winter season. *The Relative Oceanic Niño 3.4 Index (RONI) is a modern way of measuring oceanic El Niño and La Niña that is complementary to oceanic traditional indices. While traditional oceanic indices like the Niño 3.4 Index monitor SSTs in one region, the RONI compares the average SST in the central equatorial Pacific with the average SST across the global tropics. Since tropical rainfall patterns respond to changes in ocean temperatures, this new relative index can help forecasters better determine if the equatorial Pacific is warmer or cooler than the rest of the global tropics, which has become more challenging to discern as seas warm because of climate change. Forecast Confidence Notes: NIWA's outlooks indicate the likelihood of climate conditions being at, above, or below average for the season as a whole, relative to the 1991-2020 average. They are not 'weather forecasts' as it is not possible to forecast precise weather conditions three months in advance. The outlooks are the result of the expert judgment of NIWA's scientists and forecasters. 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 useful indicators of likely overall climate conditions for a season. The outlooks state the probability for above average conditions, near average conditions, and below average conditions for rainfall, temperature, soil moisture, and river flows. When a particular probability reaches or exceeds 60%, we conclude it is 'very likely'. This three-way probability means that a random choice would be correct only 33 per cent (or one-third) of the time. It would be like randomly throwing a dart at a board divided into three equal parts, or casting a dice with three numbers on it. Where probabilities are within 5% of one another, the term 'about equally' is used. All outlooks are for the three months as a whole. There will inevitably be relatively wet and dry days, and 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 for the long-term mean, whereas for rainfall the 'near normal' category lies between 80 per cent and 120 per cent of the long-term mean. The seasonal climate outlooks are an output of Predicting climate variability and change, a scientific research programme supported through NIWA's Strategic Science Investment Fund. The forecast confidence meter for temperature and rainfall represents the expert judgement of NIWA's climate scientists. It aims to synthesize various forecast elements, such as global and local climate drivers, in order to clearly communicate forecaster confidence in how all the evidence has aligned for the seasonal outlook.
The South African
07-05-2025
- Climate
- The South African
Weather: Cold warning was a hoax, here's the truth
The South African Weather Service (SAWS) has issued an urgent correction regarding a cold warning hoax. A widely circulated message warning about an alleged 27-hour extreme cold period supposedly caused by an 'Aphelion phenomenon.' Weather authorities are calling on the public to disregard and stop sharing this false information. The debunked hoax message claims that South Africans should prepare for a dramatic temperature. According to the message, the drop was set to begin at 5:00 AM. This drop would have caused the Earth's increased distance from the Sun to create dangerously cold conditions. SAWS has categorically dismissed these claims as both scientifically inaccurate and potentially harmful. While Aphelion, the point when Earth reaches its maximum distance from the Sun is indeed expected on July 3rd at 15:54, SAWS clarifies that this astronomical event does not cause significant temperature fluctuations. Weather experts emphasise that Earth's seasons are determined by the planet's axial tilt, not its orbital distance from the Sun. Contrary to the hoax's warnings of extreme cold, SAWS's seasonal climate outlook released on May 2nd, 2025, actually forecasts 'higher than normal minimum and maximum temperatures' for most regions of South Africa this winter. Only the southern coastal areas might experience 'cooler than normal temperatures' due to regular winter weather patterns such as cold fronts. SAWS also notes that the El Niño–Southern Oscillation (ENSO) has returned to a neutral state, meaning this climate pattern is unlikely to have a significant impact on South Africa's winter weather conditions this year. Let us know by leaving a comment below, or send a WhatsApp to 060 011 021 1 Subscribe to The South African website's newsletters and follow us on WhatsApp, Facebook, X and Bluesky for the latest news.
The South African
04-05-2025
- Climate
- The South African
SAWS refutes viral cold spell warning
The South African Weather Service (SAWS) has dismissed a widely circulated message on social media that falsely claims South Africa will experience an extreme cold spell until August 2025 due to the 'Aphelion phenomenon.' Officials have urged the public to ignore and avoid sharing the misinformation, citing the scientific facts behind the country's seasonal patterns. 'The Aphelion is the point in Earth's orbit where it is farthest from the sun. According to research, it is expected to occur on 3 July at 3:54 pm,' SAWS confirmed. However, the agency explained that this astronomical event has no real impact on temperatures. Rather than bracing for a year-long chill, South Africans should prepare for a relatively mild winter. According to SAWS, the current official forecasts suggest warmer-than-usual conditions across most of the country. Minimum and maximum temperatures are expected to remain above normal throughout the season, though occasional cold fronts and cut-off lows may still bring temporary drops in temperature. Some southern coastal areas may experience slightly cooler weather, but these instances remain consistent with normal seasonal variations. The weather service also addressed the influence of global climate systems, noting that the El Niño–Southern Oscillation (ENSO) has returned to a neutral state. As a result, it is expected to have minimal effect on South African winter weather this year. Additionally, below-normal rainfall is anticipated in the south-western interior and coastal regions across all phases of the winter season. SAWS calls on the public to rely on verified sources and official updates to avoid unnecessary alarm. Let us know by leaving a comment below or send a WhatsApp to 060 011 021 1. Subscribe to The South African website's newsletters and follow us on WhatsApp, Facebook, X and Bluesky for the latest news.
USA Today
03-05-2025
- Climate
- USA Today
Major climate pattern shifts ahead of hurricane season, bringing new risks
Major climate pattern shifts ahead of hurricane season, bringing new risks Show Caption Hide Caption Active 2025 hurricane season forecast A meteorologist warns of an active 2025 hurricane season. Among the areas most at-risk of potentially getting hit by hurricanes are the Gulf Coast and the Carolinas. La Niña conditions have ended, transitioning to a neutral phase, which historically has produced both active and quiet hurricane seasons. Neutral conditions typically favor Atlantic hurricane development due to lower wind shear, but "warm neutral" conditions can slightly decrease activity. Regardless of seasonal forecasts, individuals should prepare for potential hurricanes, as even less active seasons can produce powerful storms. Hurricane forecasters are carefully watching ocean temperatures in the Pacific Ocean for changes that signal El Niño or La Niña, major global climate patterns that affect hurricane season outlooks. On Thursday they announced La Niña conditions had ended after just 3 months, and a neutral period had begun — a scenario that has fed both devastating and mild hurricane seasons in the past. La Niña, a natural climate pattern, is marked by cooler-than-average seawater in the central and eastern Pacific Ocean, and is part of the El Niño – Southern Oscillation (ENSO) cycle, which can significantly impact weather patterns globally, especially during late fall, winter, and early spring. La Niña also acts to boost Atlantic hurricane activity. Its opposite is El Niño, which is a natural climate pattern where sea surface temperatures in the central and eastern tropical Pacific Ocean are warmer than average, occurring roughly every 2-7 years, and also part of the broader ENSO cycle. El Niño typically diminishes Atlantic hurricane activity. A top hurricane forecast brings bad news: Danger is already brewing ENSO-neutral is an intermediate phase between El Niño and La Niña when water temperatures are neither unusually cold or warm. What happened to La Niña? A weak but drought-spawning La Niña officially came to an end this week, federal climate forecasters announced Thursday morning. In its immediate place will be so-called "ENSO-neutral" conditions, which are forecast to last through the summer. ENSO-neutral, when neither El Niño nor La Niña conditions are present, have been reported during catastrophic hurricane seasons in the past. What effect has ENSO-neutral had on hurricane seasons in the past? Typically, ENSO-neutral is favorable for Atlantic hurricanes, like La Niña, because of lower wind shear over the Atlantic, meteorologist Andy Hazelton told USA TODAY. "Sometimes, if it's 'warm neutral' (warmer than usual in the equatorial Pacific but not quite warm enough to officially classify as El Niño), it can lower activity a little bit." What kind of risks come with an ENSO-neutral season? "Some old work suggested increased hurricane risk to Florida during ENSO neutral seasons," Hazelton said. "I don't think that work has been updated with the last decade or two of activity, though, so I'm not sure the relationship still holds. Because of the lower shear during La Niña or cool neutral seasons, there is a general risk of more hurricane activity in the Caribbean/Gulf/West Atlantic." An infamous neutral phase hurricane season The incidence of hurricanes is higher during the neutral phase (when neither El Niño nor La Niña are in effect) than during El Niño, according to the National Weather Service. Although hurricanes occur more often during La Niña episodes, significant tropical weather events have occurred during the neutral phase. For example, the record-shattering 2005 hurricane season that included Katrina and Rita occurred during the neutral phase. But conditions elsewhere were different in 2005: "2005, which included Hurricane Katrina, was a neutral ENSO, but also had a very warm Atlantic 'Main Development Region,'" Hazelton said. "The Atlantic sea-surface temperature configuration we have now isn't quite that favorable. Those two pieces (ENSO and Atlantic water temperatures) are both critical for how the season evolves." Colorado State University hurricane researcher Phil Klotzbach agreed, telling USA TODAY: "we currently don't have 2005 as an analog for our (2025) forecast. The Main Development Region isn't currently looking quite as conducive as it did (from an anomaly perspective) during the peak of the 2005 season." What does ENSO-neutral mean for the weather? "The biggest take away is that ENSO-neutral means there is no El Niño or La Niña present to shove the global atmosphere around in a systematic, predictable manner," federal climate scientist Michelle L'Heureux told USA TODAY. "So, if you look at the Climate Prediction Center's seasonal outlooks right now you still see odds in favor of certain temperature/precipitation outcomes, but they are not necessarily caused by La Niña and can be attributable to other factors," she said. "Now, I should caveat that by saying that there could still be some lagged impacts from the La Niña and it could slightly influence the near-term to some degree (late spring/early summer). But it's not possible for us to quantify 'this part is a lagged influence from La Niña and this part is something else.'" Start preparing now for hurricane season People should prepare for the season regardless of the activity forecast, Hazelton suggested. There are busy years with a lot of impacts like 2005 or 2024, but there are years with a lot of activity but few impacts (like 2010). "On the other hand, 1992 only had a few hurricanes, but one of them was Andrew. Similarly, 2019 (which was a warm neutral year) didn't have a lot of activity, but did feature Dorian, which was a long-tracked Category 5 that devastated the northern Bahamas and came very close to hitting Florida. "Regardless of how the seasonal activity pans out, it's possible you'll get a bad storm where you live, and you should be prepared just in case," Hazelton said.
