North Island Cold Pool- 18th April

Tornado Tim · Unread post by **Tornado Tim** » Sun 17/04/2011 10:33

Looks like a cold pool will cross the CNI tomorrow with scattered heavy showers with hail and a fairly good chance of thunder with it.

SFC temps are expected to be in the cooler side (around 17Â°C) but with upper air temps being very cold down to -30Â°C the lapse rates should be good.

Lifted Indices and TT Index values are looking favorable for some thundery convection.

Areas I think would get a fair to good chance of thunder would be Waikato/Waitomo and then BOP/Eastern Coast Line later on.

NZstorm · Unread post by **NZstorm** » Sun 17/04/2011 11:54

My thoughts are for thunder up the east coast of the North Island tomorrow. Quite deep layer cold instability there with showery onshore flow.

Tornado Tim · Unread post by **Tornado Tim** » Sun 17/04/2011 12:00

GFS has been picking the CNI scenario for quite a while and only just recently changed to the Eastern coast and now has flicked back to the CNI again.

spwill · Unread post by **spwill** » Sun 17/04/2011 12:16

Will watch with interest Tornado Tim.

Away from the warmer/seabreeze part of the year I prefer to see the colder upper air have more of a sea track and less land track for thunder on the west side of the Island

NZstorm · Unread post by **NZstorm** » Sun 17/04/2011 12:36

I think thunder could possibly occur over the Taranaki region and coastal Waitomo tomorrow as well.

NZstorm · Unread post by **NZstorm** » Sun 17/04/2011 18:46

Using the 400mb chart you can better pinpoint where the coldest upper air will be tomorrow. It looks favorably cold over the eastern NI. Any thunderstorms will be electrically weak but there could be isolated heavy falls of small hail.

Chart is 400mb (6000m) temperatures at midday on todays 00Zgfs.

Tornado Tim · Unread post by **Tornado Tim** » Sun 17/04/2011 20:21

I would still count the CNI has some risk rather than none at all.

Will have to see how the day pan out tomorrow......

Manukau heads obs · Sun 17/04/2011 20:37

in Palmy 2 nite, so mite get some CB's on the ranges tomorrow?

NZstorm · Unread post by **NZstorm** » Mon 18/04/2011 06:59

Looks good for Gisborne getting a storm/hail around the middle if the day.

Manukau heads obs · Mon 18/04/2011 07:36

just heard thunder here in palmerston north...

David · Unread post by **David** » Mon 18/04/2011 07:59

The shower at 4.40am set a new record for my station, high rain rate 177 mm/hr. Was amazingly torrential. Rainfall graph went vertical

Rather showery this morning, though they are brief.

Michael · Unread post by **Michael** » Mon 18/04/2011 08:28

Just outright horrible,leaves and needles,Is worse than the wind the week before which was more westerly.

jamie · Unread post by **jamie** » Mon 18/04/2011 09:35

David wrote:The shower at 4.40am set a new record for my station, high rain rate 177 mm/hr. Was amazingly torrential. Rainfall graph went vertical Rather showery this morning, though they are brief.

at my flat we had an absolute torrential downpour some time between 3 and 5. bloody heavy but my station at my parents didnt get it.

David · Unread post by **David** » Mon 18/04/2011 09:47

jamie.haultain wrote: at my flat we had an absolute torrential downpour some time between 3 and 5. bloody heavy but my station at my parents didnt get it.

The one here was pretty local too. The weather station on the other side of Howick (couple of km) didn't get the downpour I got. I was lucky I guess

MS says strong SW today, still have a Westerly though at the moment.

spwill · Unread post by **spwill** » Mon 18/04/2011 09:51

Thunder here just now from a shower cloud over West Auckland direction.

bmo · Unread post by **bmo** » Mon 18/04/2011 09:53

David wrote:The shower at 4.40am set a new record for my station, high rain rate 177 mm/hr. Was amazingly torrential. Rainfall graph went vertical Rather showery this morning, though they are brief.

Must have been a wide shower band as all the way over here at 4:44am rainfall rate was 21.6mm/hr which is the highest today and i'm a fair way of Howick!

NZstorm · Unread post by **NZstorm** » Mon 18/04/2011 09:54

Thunder here just now from a shower cloud over West Auckland direction.

I heard that too. A decent looking shower to the west.

ricky · Unread post by **ricky** » Mon 18/04/2011 09:54

Radar is showing likely Hail in that too..

bmo · Unread post by **bmo** » Mon 18/04/2011 10:01

Here is a pic of the clouds over Auckland 5 minutes ago, saw some lightning in the distance.

Michael · Unread post by **Michael** » Mon 18/04/2011 10:06

Definitly SW here pine needles over the buckling windows,wind whistling.

David wrote:
MS says strong SW today, still have a Westerly though at the moment.

David · Unread post by **David** » Mon 18/04/2011 10:09

NZstorm wrote: I heard that too. A decent looking shower to the west.

Too far east here to hear any thunder. Big dark cloud just went over and all it gave was a brief light shower - bit disappointing lol

C-Nimbus · Unread post by **C-Nimbus** » Mon 18/04/2011 10:11

Man that was epic!

Thunder straight over head about 15 mins ago....gave the dog a huuuuge fright

All over pretty quickly tho. Its my favourite kind of weather this, the unstable SW flow with cold Cb's

bmo · Unread post by **bmo** » Mon 18/04/2011 10:28

Temp has dropped 2 degrees in 15 minutes, it was 17.5 now 15.5 and dropping. Have lit the fire for the second times this year.
*Update make that 13C and dropping*

Orion · Unread post by **Orion** » Mon 18/04/2011 10:35

Hope my Auckland family has their winter woollies hunted out! Keep warm, folks.
(6.5 degrees here now)

GraemeWi · Unread post by **GraemeWi** » Mon 18/04/2011 11:08

Hail here in Henderson, West Auckland. Had one good thunder earlier today.

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North Island Cold Pool- 18th April

North Island Cold Pool- 18th April

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