The term 'Marangai' means east wind, also meaning a storm, or bad weather. However, in some districts, Marangai means the north wind. It is likely that its meaning depended on the quarter from which bad weather tends to come in that district. Over the last week the upper North Island experienced an extreme weather sequence in what could only be called the Great Marangai. Sadly this weather sequence caused a loss of life, extensive property / infrastructure damage and countless landslides.
Here is the some of the important meteorological factors and timeline of events that took place.
Jan 21st – Joint Typhoon Warning Centre names Tropical cyclone 10P near New Caledonia. It only remained a cyclone for less than 1 day.
Jan 24th - The Australian weather model Access G starts to project 300mm+ rainfall event for Auckland and the Coromandel for the 26th/ 27th January. No other models looked this extreme but ultimately this would be an important hint of what was to come.
Jan 25th - Ex-tropical cyclone 10P connects with a mid-latitude trough which is dragging down large amounts of moisture from the tropics through an atmospheric river. Total precipitable water values have now increased to 50mm.
A new upper trough moves in from over the Tasman reinvigorating ex-tropical cyclone 10P.
Jan 26th - Ex-tropical cyclone 10P develops into deeper subtropical low with a rainband extending ahead of a warm front into Northland.
MetService issues widespread upper North Island 'Orange' heavy rain warnings.
Jan 27th - On sunrise, early signs of a significant rain event appear on water vapour images north of Northland.
King tide arrives across the Upper North Island
A significant convergence zone develops from lower Northland to southern Auckland from 2:00pm
Devastating and deadly flooding starts to appear in Auckland city, suburbs and roads as inundated storm water systems overload beyond capacity. 200 to 370mm was recorded in areas under the convergence zone.
1st severe thunderstorm warning was issued by MetService 4:18pm, 27th January.
MetService issues 1st RED warning for Auckland and Great Barrier Island at 9:07pm, 27th January. State of Emergency was issued by Auckland Council at 9:27pm. No emergency alert was sent by NZ Civil Defence for the day.
Jan 29th - A 2nd new upper level trough launches over the central Tasman, creating 2 new upper lows and a Fujiwhara effect.
Jan 30st - A large baroclinic leaf appeared along with a water vapour surge with equatorial origins. A consolidated upper low near Norfolk Island was in place to trigger the development of a surface low in the subtropics.
MetService issue a new Red warning for Northland, Auckland and the Coromandel
Jan 31st - Sunrise satellite imagery shows a new subtropical low with developing low-level Jetstream.
Wind gusts in the gulf clocked 64 knots 119 km/h the subtropical low deepened below 1000 hPa.
Feb 1st - A new convergence zone forms over the Gulf and moves over Auckland before sunrise. another 80 to 110mm falls on the city in only a couple of hours exacerbating and causing more flash flooding issues.
Feb 3rd - A final round of light to moderate rain fell across the upper North. Bringing to a close the most extreme rain event ever recorded in New Zealand's modern history for its most populated region.
Here are the final rainfall totals over 8 days from 27th January to 3rd February 2023 across the upper North Island recorded on private online gauges.
572 Hobsonville point
520 Albany
520 Sunnynook
514 Glenfield
503 Paremoremo
502 Greenhithe
500 Bayswater
495 Mt Eden
484 Orewa
483 Birkenhead
476 Torbay
467 Herne Bay
466 Wellsford
461 Auckland city
461 Beach Haven
458 Browns Bay
456 Mairangi Bay
453 Northcote Point
450 Campbells bay
449 Swanson
446 Puhoi
441 Beachlands
440 Chatswood
440 Warkworth
440 Kumeu
439 Castor Bay
439 Milford
439 Murrays Bay
427 Coatesville
421 Millwater
421 Silverdale
414 Epson
411 Belmont
405 Gulf harbour
404 Clevedon
403 Titirangi
400 Huapai
399 Stanmore Bay
399 Dairy Flat
398 Grey Lynn
388 Birkdale
385 Devonport
385 Matakana
378 Leigh
377 Pataua North
374 Waiuku
370 St Heliers
366 Awhitu Peninsula
365 Riverhead
364 Coromandel town
359 Great Barrier Is
358 Kaipara Flats
349 Whangamata
349 Pauanui
347 Kaiwaka
347 Whangaparaoa
346 Mangawhai
344 Algies Bay
343 Henderson
342 Ellerslie
340 Mission Bay
332 Pukekohe
327 Huntly
317 Whitianga
315 Waiheke Island (Omiha)
311 Te Mata
302 Omaha
293 Port Waikato
290 Waihi
287 Glorit
278 Kopu
275 Waiheke Island (Onetangi)
271 Whenuapai
267 Thames
265 Papakura
264 Tauranga
261 Hamilton
260 Howick
257 Matarangi
251 Wharekawa
243 Kaukapakapa
237 Langs Beach
235 Bucklands beach
233 Whangarei
228 Ngatea
225 Waipu
223 Hunua
219 Ruakaka
214 Matapouri
214 Tutukaka
210 South Head
200 Waiheke Island (Matiatia)
192 Kerikeri
185 Helensville
185 Bombay
174 Muriwai
102 Dargaville
Note: With heavy downpours, some localised large differences can occur between close gauges