NZ Weather Forum

We have had some very interesting echoes appearing on radar over the last few evenings soon after sunset. These have been seen on the Auckland, Taranaki, Wellington and Canterbury radars in the last few days, especially in the Auckland area.

Has anyone noticed a significant increase in insects flying during the evening hours? Perhaps there has been a recent hatch of moths or flying ants or something else? And the echoes last for most of the night hours.

It seems that the recent very warm moist conditions with light winds are playing a part.

Cheers,

Paul

we have alot of crickets around here at the moment...
(due to cracks in the ground I would say...good breeding places)

We have tons of mosquitoes at night but thats normal.

Lots of moths down here in West Melton in the evenings, Paul.

JohnGaul
NZThS

how high in the sky would they be Paul? for it to be picking up echos?

Thanks for your replies.

The echoes are very low down - at the bottom of the beam within (from memory) about 50-80km of the radar.
They rise into the beam and then drift with the prevailing flow. We don't think they are birds because birds often can be seen returning to spots they fly from (in the morning hours - overnighting on lakes etc). We sometimes see birds coming and going from areas in Canterbury - like Lake Ellesmere.

Paul

Just had a thought - maybe bats?

John, I've noticed that have had more of the larger moths lately too - ones about 0.75 to 1inch long.

Paul

Paul Mallinson wrote:Just had a thought - maybe bats?

John, I've noticed that have had more of the larger moths lately too - ones about 0.75 to 1inch long.

Paul

Bats in Auckland really? LOL
I know that the Waikato gets full up of moths at night time, that might be another cause perhaps?

Interesting.. could they be locusts? I just don't recall seeing too many locusts in NZ that's all...

February for Hamilton, at least can be absolutely shocking for crickets after hot weather.. but they don't fly that high I'd imagine?

Paul are you talking about the echos currently on the auckland high res radar that have just built in the last hour? if it is its not very isolated. its everywhere. very strange

i have noticed an amazing amount of flies and other insects in the grass air above the ground since the rains. so much so that in the morning i cannot drive with the lights on on the motor bike and i go on moon light or atm on the glow from hamilton to see my way around but i couldnt imagine its flies and other bugs surely.

If it what is visible on the hires radar images it does seem that those patches of echoes all start more concentrated at areas of higher ground before spreading while moving.. are they always in the same places?

Yes, they do start from much the same areas each time and appear from about 8:30pm.

They did occur again last night as jamie.h thought. The echoes were weaker last night.

I had a look back at the night before again for Auckland (night of Feb 19) and the echoes were quite strong with a sse to nnw drift. A cross-section showed that the echoes were as much as 2 kms deep.

The more I think about it, the more I'm convinced these are from insects. The echoes occur over a large area and are quite uniform.

Paul

I think they're probably insects as well as they seem to be drifting with the wind. They all appear quite quickly around or shortly after sunset, and appear to come from bush covered hills, mountains and islands. I'm wondering if they are moths.

If it was my guess and it was insects cicadas would be on top of that, they seem to have increased over the last few days at home, why they are becoming more active I wouldn't know why.

also to add if there was more insects about at evening, then there should also be more birds about, may add to what's showing on the radar.

im seeing the weird rain return on the wellington radar right now. it looks like moderate to heavy rain. how strange.

im seeing the weird rain return on the wellington radar right now. it looks like moderate to heavy rain. how strange.

I believe its caused by a low level temperature inversion.

NZstorm wrote:

im seeing the weird rain return on the wellington radar right now. it looks like moderate to heavy rain. how strange.

I believe its caused by a low level temperature inversion.

Could be, but there is a very definite drift in the echoes that is consistent with the prevailing boundary layer wind.

In my experience, I don't think Cicadas fly at night.

Paul

In my experience, I don't think Cicadas fly at night.

Good point!

im really eager to know what is causing this. very strange

NZstorm wrote:

im seeing the weird rain return on the wellington radar right now. it looks like moderate to heavy rain. how strange.

I believe its caused by a low level temperature inversion.

NZstorm is correct. The echoes on the Wellington radar this evening are due to ducting, which occurs due to high super-refraction in the lower atmosphere from strong low-level temperature inversions. The radar beam is being bent down onto the sea surface, and it is this which is giving the false echoes.

Here are a couple of links...

http://www.theweatherprediction.com/habyhints/247/

http://www.theweatherprediction.com/habyhints/234/

This is quite different to the 'insect' echoes we were seeing a couple of days ago.