Small Funnel Cloud

[GreggWard]

This afternoon I noticed a small funnel cloud extending down from a line of Towering Cumulus located somewhere between Palmerston North and the Foxton Beach area, to my SW.

The cloud from which the funnel had extended was moving NW in a SSE that was blowing showers off of the Tararua Ranges across the Manawatu.

When I first noticed it, it appeared as a small thick stovepipe shape extending at least a third of the way from the cloud-base to the ground. This was around 14:40. I watched it until around 14:50, with it gradually thinning out in shape and lengthening slightly and then gradually shortening back into the base of the cloud.

This is the second time I have seen a funnel cloud in a similar area and weather situation, during the Summer months. It appears to happen when there is a SSE blowing across the Manawatu that meets up with the local Sea Breeze that blows in from a SW-W direction, along with some afternoon convection.

I was viewing it from the third floor of the building from where I work and that I had had access to a Digital Camera.

I have attached the 16:00 radar image which shows the same group of showers out to the SW-W of Palmerston North.

[Thunder]

Do you mean you wish you had had access to a digital camera, if so, I could understand that. Next summer then! I guess this shows rare things can occur even with Cu, thanks for the report.

Cheers
Aaron Wilkinson

[GreggWard]

Yes that was what I meant.



Gregg

[tich]

Gregg, did you notice any thunderstorm activity with the cloud that produced the funnel? I recall isolated thunderstorms were forecast for the central and northeastern North Island yesterday, but not for the southwest.
It looks like the North Island is in quite a cold (for December) southerly/southeasterly flow. I see MetService has the North Island freezing level at only 1400 metres this morning, though rising considerably this afternooon. That should mean (depending on the available moisture) snow showers on the mountains as low as 1100 or 1200 metres - quite wintry for the time of year (and a big change form the sub-tropical conditions of late).

[NZstorm]

I don't think it got that cold Ben.

NZPP freezing levels have ranged from 2200m last night to 3100m today.
NZWP 2800m to 3200m.

This cam gives a good panorama of Mt Ruapehu.

http://www.geonet.org.nz/images/ruapehu.jpg

[tich]

I don't think it got that cold Ben.

NZPP freezing levels have ranged from 2200m last night to 3100m today.
NZWP 2800m to 3200m.

The MetService mountain forecast this morning predicted the freezing level over the North Island to be about 1400 metres, rising to 3000 metres this afternoon. Perhaps they made an error saying 1400 metres - could they really have meant 2400 metres?

[GreggWard]

Ben,

I didn't notice any thunderstorm activity associated with the cloud that produced the funnel, however it was surrounded by some pretty dark and menacing looking shower clouds. There was quite an intense shower coming off the Tararuas at the time, to the SE of the area where the funnel was spotted.



Gregg

[TonyT]

Ben - it depends on how they calculate the FZL. If you use the model profile data without any checking you can sometimes get caught out because in the early morning the model makes the temps colder due to night time heat loss, and the freezing level appears to fall at that time (which in reality I suppose it does in a local, micrometeorological sense). But that is not representative of what we might call the free-air, or mixed-air freezing level, which will stay much the same throughout the day unless the airmass temperature changes. The FZLs Steven quotes from NZPP come from the balloon ascent there, and with some wind and mixing they will represent the free-air FZL. However, if you were on top of a 1400m mountain at 6am you might well have measured an air temp of about zero degrees. Does that make sense?

[Weather Watcher]

You also need to be careful on what height is quoted as the freezing level. Attached is the actual skew-T diagram from Paraparaumu at 17/00z (even though University of Wyoming files it as 16/21z). On the diagram there are actually two freezing levels, one around 1500m (at the inversion) and a second around 3100m. I think it is the meteorological convention to quote the highest number as the official "freezing level" for that station.