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NELSON, July 2, 2025
South Island communities on edge.
Already reeling from deadly floods, Nelson and Tasman brace for another weather onslaught.
- Orange rain warnings issued for parts of Tasman District.
- Residents urged to evacuate early from at-risk areas.
- millions of dollars in damage already reported from previous flooding.
- Auckland and other North Island regions also under weather watches.
What is causing the severe weather in New Zealand? The severe weather is attributed to a large low-pressure system and associated fronts, including remnants of an Australian ‘bomb cyclone,’ bringing widespread rain and potential flooding to the region.
Flood-stricken communities in Nelson and Tasman are bracing for more severe weather. Local Civil Defence is preparing for another onslaught of rain. New severe weather warnings have been issued, impacting not only the top of the South Island but also extending across the upper North Island.
Warnings extend to North Island
Auckland, Northland, Bay of Plenty, Waikato, and parts of Taranaki and Gisborne are under orange warnings or yellow watches. A large low-pressure system is bringing widespread severe weather.
Orange rain warnings are in effect for Tasman District northwest of Motueka from 3 a.m. to 6 p.m. Thursday. Rainfall is expected to reach 120-150mm, with localized areas potentially seeing up to 200mm.
From 6 a.m. to 9 p.m.,Tasman and Nelson districts,around and southeast of Motueka,can expect 80 to 110mm of rain about the sounds and ranges,and 50 to 80mm elsewhere.
Dan corbett says remnants of Australian ‘bomb cyclone’ to impact NZ.
Communities prepare
Tasman Mayor Tim King said residents are “doing what communities do” to prepare for the impending weather. MetService indicates a low chance that orange warnings will be upgraded to red.
“They’re helping people to prepare for this next lot of rain,” King said. “Whether that’s sandbagging,moving stock,trying to fix the damage on properties,the contracting people who are out fixing council infrastructure,roads,bridges,again,trying to put in temporary fixes to prepare for that coming forecast.”
Orange rain warnings have also been issued for parts of Tairāwhiti/Gisborne and Bay of Plenty. Yellow rain watches are in place for Auckland, Northland, and Waikato.
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‘Soul-destroying’ weather
Over 300mm of rain fell across parts of Nelson-Tasman late last week. This triggered widespread flooding, slips, and road closures. A state of emergency remains in effect.
King acknowledged the emotional toll on residents still grappling with the aftermath of the weekend flooding that resulted in one fatality and millions of dollars in damage across the region. “It is soul-destroying. For many of these property owners, this will be the biggest event that’s happened in their lifetime,” the mayor said. “the impact on people and the stress in communities is huge.”
A second bout of rain is expected tomorrow as Civil Defence prepares for the worst.
With the looming bad weather, King urged residents in at-risk areas to “leave early.”
“Please make those decisions to leave early. That’s much easier to leave early and come back if it doesn’t eventuate,and go,’gosh,you know,maybe that wasted 24 hours,’ than to try and leave when the water’s right at your back door.”
Millions in damage
Earlier this week, Nelson Mayor Nick Smith reported millions of dollars worth of damage to roads, bridges, fences, farm buildings, hop gardens, and orchards.
Flooded communities remain cut off tonight, as the full extent of the clean-up becomes clearer across the top of the South Island.
“The worst areas are Wai-iti, Tapawera, Motueka Valley, Kohatu, Motupiko, Pretty Bridge Valley, and Tadmor,” Smith stated.
The Tasman District council warned that while the forecast rainfall might typically cause only moderate flooding, the current conditions are “far from normal” due to saturated ground and damaged infrastructure.
The council provided an update from its hydrology team, stating: “While under normal antecedent conditions, these totals combined with a short duration event would produce low to moderate floods. Though, we are far from normal, with very saturated ground and compromised infrastructure.”
The council anticipates that Golden Bay’s larger rivers should handle the forecast rainfall, but smaller catchments will “react quicker.” “We can expect further surface flooding, landslipping, and road closures to already compromised roads and associated structures.”
Understanding Bomb Cyclones: What Makes Them So perilous?
The recent severe weather in New Zealand, fueled by the remnants of an Australian “bomb cyclone,” has brought increased attention to these powerful weather systems. But what exactly is a bomb cyclone, and why are they so destructive? A bomb cyclone earns its name from the rapid intensification of a mid-latitude cyclone, dropping its central pressure dramatically in a short period. This phenomenon leads to extreme weather conditions.
Essentially, a bomb cyclone is a rapidly intensifying storm. The term “bomb” refers to “bombogenesis,” a meteorological process characterized by the swift intensification of a low-pressure weather system.for a storm to be classified as a bomb cyclone,its central pressure must drop by at least 24 millibars in 24 hours.this rapid drop in pressure creates a powerful storm with high winds, heavy precipitation, and the potential for widespread flooding.
- Rapid Intensification: Bomb cyclones intensify very quickly due to a variety of atmospheric conditions.
- Pressure Drop: A key marker is the meaningful drop in atmospheric pressure over just a day.
- Extreme Weather: This leads to intense winds, heavy rain, and potential for flooding.
The power of a bomb cyclone stems from the dramatic pressure differences between the storm’s center and its surroundings.This pressure difference generates strong winds, which can cause significant damage. These storms often bring with them heavy precipitation, which can lead to flooding, especially in areas with already saturated ground, as seen in Nelson and Tasman.
The formation of a bomb cyclone requires specific atmospheric conditions. These often include a cold air mass colliding with a warm, moist air mass, typically over the ocean. This contrast creates ideal conditions for the storm to rapidly develop.The interaction of these air masses often results in the formation of fronts, which further contribute to the intensity of the weather event.
Specific Threats and Impacts
The primary threats associated with bomb cyclones include high winds, heavy rainfall, and coastal flooding. Inland, the most significant concern is often flooding caused by excessive rainfall. Powerful winds can damage infrastructure, uproot trees, and disrupt power supplies. In coastal areas, the combination of high winds, storm surge, and heavy rainfall can create devastating flooding events. The recent events in Nelson and Tasman showcase how even the remnants of such storms can pose a significant threat, particularly to regions that are already dealing with saturated ground and damaged infrastructure.
As of their intensity and rapid development, these storms can be difficult to predict precisely.Though,meteorologists use a variety of tools,including weather models and satellite imagery,to track their formation and movement. The MetService in New Zealand, for example, monitors these systems closely, issuing warnings and watches to provide valuable information to the public. Early warnings and proactive measures are crucial in minimizing the impact of these dangerous weather events.
Actionable Steps for Community Preparedness
What can communities and individuals do to prepare for the possibility of a bomb cyclone or its effects?
Having a plan and being prepared can make a significant difference.
- Stay Informed: Pay close attention to weather forecasts and warnings from official sources like MetService.
- Emergency Kit: Assemble an emergency kit including non-perishable food, water, a first-aid kit, a flashlight, a battery-powered or hand-crank radio, and any necessary medications.
- Evacuation Plan: Know evacuation routes and have a plan for where you will go if you need to evacuate.
- Home Preparation: Secure outdoor objects like furniture and garbage cans that could be caught by high winds. Clear your gutters of debris.
- Insurance Review: Review your insurance policy to ensure you have adequate coverage for potential flood damage and other weather-related events.
- Interaction: Establish a communication plan with family members, including multiple ways to contact each other.
Myth vs. Fact: Bomb Cyclones
There’s often confusion surrounding bomb cyclones. here’s a fast rundown of some common myths and the facts:
- Myth: Bomb cyclones only happen during specific seasons. Fact: Bomb cyclones can form at any time of year, provided the necessary ingredients in the atmosphere come together.
- myth: Bomb cyclones always hit with the same intensity. Fact: The strength of a bomb cyclone can vary, depending on factors like the interaction of the air masses.
- Myth: bomb cyclones are a new phenomenon. Fact: The term “bomb cyclone” has been around since the 1980s, but they’ve been around for much longer.
- myth: bomb cyclones primarily affect only coastal regions. Fact: While coastal areas are frequently enough hit hard, the effects of a bomb cyclone, such as heavy rain and flooding, can extend far inland.
The Road Ahead
As the residents of nelson and Tasman, and other regions in New Zealand and beyond, continue to face the challenges posed by severe weather events, understanding the nature of these powerful storms is vital. Education, preparation, and community cooperation are key to weathering these events. As climate patterns shift, it is expected that some areas will see an increase in extreme weather events of this nature. By understanding the science behind them and taking proactive steps to prepare, communities can reduce the risks and build greater resilience.
Knowing what to expect and how to react will empower you and your family in the face of any severe weather event.
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