Seasonal Climate Outlook - May to July
NIWA New Zealand
[{'start': '0.766', 'end': '3.833', 'text': "Kia ora, Chris from NIWA Here with a seasonal climate outlook recording this on the second day of May on a Friday. It's time to see what the next three months have in store in terms of theme. So let's go to the headlines. I'm going to disappear. And you can see in terms of temperature, a warmer than average three month period is likely for all of New Zealand. It doesn't mean there won't be cool periods. There will be. In fact, this weekend, as I say, recording this on the second day of May, there will be some cool periods, but that will not dominate or be the theme rainfall theme. Well, we got to watch for wetness, particularly for the northern part of the North Island. So Auckland, Northland, Bay of plenty, Waikato, perhaps even eastern areas of both islands, which is why there's a question mark, because a little more uncertainty there. We feel more confident for the upper North Island, however, and watching for dryness, potential dryness for the western parts of both islands over the next three months. And speaking of watching, we're watching for these big rainfall events. Our weather is going to be influence from the tropical north on occasion. Were expecting north to northeast winds as a theme, using that word again for the next three months. And that's a consequence when we get these northerly intrusions, not only will we see a spike in temperature, we'll see a spike in the odds for big rainfall events coming back on screen. So let's get, what you need to know in terms of the outlook itself disappearing once again. Yeah. It's red. You can see the entire country above average temperatures with pretty good confidence for the May, June and July period. What does this mean? Perhaps less frost than usual. Perhaps we use the heater a little bit less than usual. Maybe we sneak in some warmer days where we want to be outside. More than usual. Could be a not so hot start for the skiing or snowboarding season. Sorry to say that, but that's something that is probably more likely than not. If I'm being honest, though, we don't explicitly issue a snow forecast, with our seasonal climate outlooks. Let's go to rainfall and you can see, above normal rainfall is likely for the upper North Island. So that's this where I'm pointing to with my cursor. So the Bay of plenty, Waikato, Northland in Auckland. We think that's the most likely area or region to see above normal rainfall. So if we're going to get what are the usual conditions? Odds are greatest in this area. We still think what are the unusual conditions are possible in other areas. Just the confidence is a little bit less. So that's why we're saying normal too above normal for these kind of tealish green areas. Eastern north, eastern south as well as the top of the South Island and coming back on screen because we are expecting this air flow or our air flows to be more north and northeast than usual. Again, doesn't mean every week out of the next three months we're going to find north and northeast winds just means we're going to find probably less westerlies and south westerly in exchange for more north and northeast release. And when that happens, that does favor dryness for western areas of both islands. And this is I know this is important because obviously we've had some ongoing dryness for the region, for the Manawatu. And if we have these north, the northeast winds or these bouts with these periods, that certainly favors dryness. And because of the antecedent conditions, that is the conditions leading up to now, with that groundwater recharge this time of the year is very important to recharge the ground with all the water that has been stripped from the, from the ground because of vegetation growth, because of sun and warm temperatures and wind that we see during during the warm season. Now for the South Island, the impact is a little bit different. Two things. Obviously skiing, snowboarding. We need precipitation and if there's less of it. If you're a skier or snowboarder, that's not good. And you combine it with what I just showed you, warmer than average temperatures. You can read the tea leaves right. So in terms of the hydro catchments, that's another sort of impact. We have to be mindful of New Zealand. We generate a lot of our electricity by way of storing water. And then turning that into electricity. And a lot of those catchments are down here on the South Island. And if we haven't, basically amounts that aren't adequate, that could be a problem. Again, we're saying normal to below normal a spectrum. So a little bit of uncertainty there where we're land. Right. So that's the next three months in broad strokes. Let's talk more about the weather picture. So we're going to go to one of our favorite maps. Certainly one of my favorite maps. It's the good old fashioned pressure anomaly. As I say we are recording this on the second day of May on a Friday. So this is Saturday, the 3rd of May and just to remind you, in case you're a first time viewer, welcome. If you're a regular thank you, you can see the blue and that is lower than normal air pressure. Lousy weather. The red higher than normal air pressure. Happy weather. So blue. Unsettled red. Settled weather. Simple as that. So we can see as we work through the weekend that low pressure that gave us that really stormy weather for the eastern South Island and Wellington, that's moving away and coming in. There's look at that high pressure. So by May the 4th, which is you know what that is? I'll give you a second. I just said it. Star Wars Day, May the 4th. May the 4th be with you. We're looking pretty good. High pressure coming in and with high pressure to our west, that means southwesterly. And I'll just switch to the temperature anomaly map, and you can see the blue. So that jives high pressure. We have west to generally southwest winds usually southwest let's call it. And that promotes coolness. And we're going to see that. And you're probably thinking well geez Chris you just said it's going to be warmer than average for the next three months. Why is it cooler? Look, this is a long range outlook. We're describing Mother nature's basically her personality. A three month outlook is Mother Nature's personality outlook a weather forecast. That's her mood. Most days there'll be a line. Some days they won't. And this is just one of them. So let's go back to the pressure map. What we're expecting is that this high comes in so this would be Sunday, then here's Monday, the fifth, sixth, Tuesday, seventh, Wednesday a third. Is that what's happening around the ninth? Let's pause it. We call this ridge replacement. Here's a term. So I'll zoom out a little bit. So we got one high pressure anticyclone we call a ridge of high pressure that's pushing away over Australia southeast Aussie and the Tasman Sea. We see another emerging area of high pressure. And in between the two there is this little weakness. And when these little weaknesses emerge, that can be a conduit, that can be a highway for moisture and warmth to come in from the tropics. And you can see across the tropical north there this the shading, the blue. And this is the weather pattern we are expecting basically for the season as a whole. When I say season, that's three months. We are expecting high pressure to be generally east and southeast of New Zealand and low pressure to our northwest. And that is going to be the general theme or set up over the three month period. So when we see a pattern like I'm showing you now, this does increase the odds for moisture to come from the north. Kind of like the use an ice hockey analogy. You know, the puck kind of slipping through the, the goalie into the net. It's could be a, it could be a thin window of opportunity. But,  this is something we'll have to watch for, because whenever our air comes from the north, obviously it's warm, but it could be quite wet. And this is when we can get those big heavy rain events. So let's play this out. We can see that is a period we'll have to watch the end of, week one, particularly the start of week two, I should say the 10th, the 11th, something like that. And if I zoom out and take this to the end, I think this really encapsulates the next three months quite nicely. So I've zoomed out and you can see not one, not two, but three anticyclone or high pressure areas. These areas of right I'm pointing to. And if you can you can look between each one right here and right here. There is this weakness we call it between the ridge replacement or when one high pressure goes away and another one is coming in between those two, there's this weakness or this opportunity for something to slide down from the north. Now, it all depends. Is there anything up north to kind of come down. So that's a that's a separate issue. But because we are going to see this propensity or this favoring of low pressure and moisture to our north, that increases the odds to see these big rainfall events, whenever one high moves east and before another high can cruise on in from the west. And this really summarizes our next three months quite well, what you can see right here. So let's take a look at once again at temperatures, you can see this is our temperature anomaly. We're looking at about 1500 meters above the ground or thereabouts. This kind of gives us an idea as to what kind of flavor the air is going to have. Is it going to be cool or is it going to be warm? And these are again anomalies. So warmer than usual, cooler than usual. And no, when that ridge or anticyclone moves to the east, we get our northerly flows. And when we get we get warmer temperatures. So after a cool period late in the weekend, early in the week of the first week of March. So like the fourth, the fifth, the sixth to seventh, we are going to warm up. You can see here's the eighth, here's the ninth. So things will warm up. And that'll be the pattern we're looking at over the next three months. Now let's go to our rainfall for the next three months. Not that's NIWA 35. There we go. We're going to go to. Where is NIWA 35? Bear with me. Here it is right here, kids. So rainfall for the next five weeks. So this is for the seven day period from the 30th of April. So this takes us from the 30th of April to the 6th of May. And with that high coming in, that makes sense. Drier than usual conditions. Now you're seeing this green down here. Look, I'm going to this green is because of the rain that already happened. So it's kind of in the rearview mirror. This starts on the 30th of April. You can see that. And we know there was a bunch of rain in Canterbury, a bunch of rain for the lower North Island and wind for that matter. So that's why you're seeing that green there. So you can almost kind of mentally ignore that, if you will. So let's move through the next five weeks. Look at that. So for the seven day period from the 7th of May. So this is saying from the seventh to the 14th, much of the North Island, especially the northern part, there's a good chance for a period of above normal rainfall and even western and upper portions of the South Island. And again, that makes sense if we recall going back to this map. Look at this. Here's the ninth and the 10th. And there is that weakness. Remember we talked about one high pressure moving away, another one coming in. But in between the two here is this highway that can allow for a moisture train to come down from the north. So that jives that makes sense. All right then let's go to week three. Things dry out. It looks like eastern areas may be favored for some wetness in week three, but it looks like dryness unfortunately returns for the scattered anarchy region and a good chunk of the South Island, though the northern half looks to be neutral. So, perhaps not drier than usual. Also, keep in mind drier than usual doesn't mean zero rain, it just means less than usual. All right, let's continue forward. So for the last. So for the 21st to the 28th of May, you can see dryness is favored for the upper North Island, perhaps some residual wetness for the eastern part of the North Island, and maybe some pockets of wetness favored for the upper and eastern South Island. But much of the country in that neutral. So normal, near normal rainfall. And finally going pretty far out there. Week five. So this takes us from the last few days of May into even the first few days of June. So I think the 3rd or 4th of June, this would be and it looks like dryness may be a theme for the South Island. We'll see. Dryness is favored for, for the western part of the North Island. So that takes us through the next three months. So that is basically the next one month, I should say the next five weeks. The next one month. Now, can we get nerdy? Of course we can. Let's get nerdy. Go to SST, sea surface temperatures. So okay, why do we do this? Because this is the engine room. This shows us where there is unusual, warm and unusually cool ocean temperatures. And as I play this through, we start off on the 7th of March and we had putting we get my, get my cursor. That's that's just not very bold. Maybe something bolder. That's better. Yeah, we'll go with that. All right. So what we're looking at here is this was La Nina. You can see how I'm circling that we had cooler than usual ocean temperatures in the tropical Pacific. Again. This is back in early March. Right. And as I put this into motion, I'll clear that away. Watch how that blue kind of fades away. Certainly it's still there, but it's not as blue. And this is a sign that La Nina is starting to fade away. In fact, we are in what we call Enso neutral. And so NSO, El Nino, Southern Oscillation, we're neutral. So La Nina is a cool phase of and so, El Nino is the warm phase event. So and if we're not in La Nina, we're not in El Nino, we're neutral. And that's what we're going to be in. But because we still see these tinges of blue, we are expecting these periods of La Nina like weather. And what I mean by that is not that one I do want to show. Yes, this one, this is a great way to illustrate that La Nina, like weather, means those weather systems dropping down from the north. So what you're looking at here is good old friend velocity potential, where you see the warm colors, the reddish, the rusty orange. I suppose part of me that's where we're seeing sinking. So we're looking at the top of the atmosphere really high up, like 200 hectare. Pascal, really high up. And where we have sinking that promotes dry weather, settled weather, where we have lift or rising, which is what you see around New Zealand and especially to the north, that promotes rainfall, unsettled weather and watch what happens in May. Well, first of all, we have that in April. Here is May kind of goes away in June. So we may see a period of perhaps settled weather in June, but then in July, look at that. We start to see more in the way of that rise. Let's go to August. Oh boy. And September. So while there will be a little bit of back and forth, a little bit of ping pong table tennis with the velocity potential potentials, May and June, you can see perhaps, opportunities for wetness with this rise favored around to our north of New Zealand. And that is forecast to give away to perhaps some sink so we could see less in the way of rainfall events potentially in June. But that returns in July. So the message is that we have to watch the North, particularly when we have this rising air around and to our north of New Zealand, because that is a source of these rain bearing events coming from the tropics and the subtropics. And that could really start to come into play, especially in July and August. So while May may feature these opportunities of wet weather to the north, at least 1 or 2 of these opportunities, June we may, June, May we may see that being dialed back. I think July and August, they could be especially wet. So the message is that I think the latter part of this three month outlook, i.e. July, that appears to have the greatest chance for having more persistent and potentially heavy rainfall events, as we see more in the way of influences coming from the north. So once again, just in summary for the next three months and then we'll wrap it up, here's what we're expecting across the country. Getting back to my there we go. Here it is. I'll disappear. Warmer than average across all of the country. Yes, there'll be cool spells, but we expect warmer than average temperatures to dominate because we're going to fine our air flows. Favoring the north and northeast, i.e. less southwesterly winds. Doesn't mean they won't occur just probably less than usual. And for rainfall over the next three months, we think the best chance for above normal rainfall is going to be in the upper North Island Bay of plenty, Auckland in Northland, Waikato, for the western part of both islands, Taranaki and Manawatu especially, we'll have to watch for the ground water recharge. That could be slow because of the antecedent conditions, the i.e the dryness that we've experienced previously and the expectation that rainfall may not be abundant, may not be abundant. So that's normal or below normal. Same could be said for the western South Island. Got to watch the hydro catchments and for the skiers and snowboarders. Could be tough, could be tough. We'll see. And then for the eastern part of both islands, as well as the top of the South Island, we think, well, there could be above normal rainfall. The confidence is not so great. So that's why we're saying that spectrum of normal to above normal back on screen, I am. So there it is the next three months. Go to Niwa.co.nz if you want to have a read of the next three months of the SCO there is a technical discussion in the bottom and that really dives into the detail. If that's something that spins your wheels, it does spin my wheels off and do read it and I help write it. So there you go. Nico actually does most of the writing. A big shout out to Nico. We'll see you next time. I'm Niwa forecaster Chris Brandolino ngā mihi nui."}]