Severe Thunderstorm Watch

Message type: Alert
Hazard type: Weather
Urgency: Future
Severity: Moderate
Certainty: Likely
Recommended Action: Make Preparations
Effective Date: December 4, 2018
Effective Time: 8:30 AM
Expiry Date: December 4, 2018
Expiry Time: 9:00 PM
Who is issuing this alert: EMS
Description of event/hazard:

Warm and moist conditions at low levels are conducive to thunderstorms over the southeast of the South Island this afternoon and into the evening. There is a moderate risk of SEVERE THUNDERSTORMS with localised downpours, 25 to 40mm per hour in Clutha and Southland.

Rainfall of this intensity can cause surface and/or flash flooding, especially about low lying areas such as rivers or narrow valleys.

An intense trough is expected to move west onto the west of the South Island this afternoon. This trough is likely to be accompanied by thunderstorms and there is a moderate risk that a few of these may be SEVERE with hail larger than 20mm and one or two localised damaging tornadoes.

Large hail can cause significant damage to crops, orchards, vines, glasshouses and vehicles, as well as make driving conditions hazardous.

Squally winds and possible tornados may cause some structural

damage, including damage to trees and power lines, and make driving hazardous.

If any tornados occur, they will only affect very localised areas.

Note: A Severe Thunderstorm Watch means conditions are favourable for severe thunderstorms in and close to the watch area. People in these areas should be on the lookout for threatening weather conditions and monitor for possible Severe Thunderstorm Warnings.

What Should affected people do?

For information on preparing for and keeping safe during a storm, see Civil Defence Never Happens Happens website

Contact Info: