Possible Ex-Tropical Cyclone from 13/14 Feb

[harleyb]

What are the chances...?

[spwill]

Just something to watch at this stage.

[harleyb]

Agree, still early days especially as the cyclone is still just forming. A forecast map to remember though, hey?

Interesting too is the possibility of interaction with an incoming cold trough from the SW. Could well be an interesting week coming up.

[Razor]

Since this is in the media now, and modelled only a few days away now within coee of NZ I thought I'd make a new thread. Even if it fizzles, its one worthy of finding later

[David]

There is a lot of disagreement in the models. GFS is the only one bringing it down onto NZ currently.

[Bradley]

EC wants absolutely nothing to do with it at this stage, let's see what tomorrow mornings run brings

[dizzy]

I just saw a headline on WeatherWatch's page saying "Cyclone heading for NZ" and then in his video he said 60% confidence of a direct hit. But then I saw a Stuff article where someone from MetService said basically what you guys are saying - that it's one to watch but too early to make a call. What does WeatherWatch have that no one else does that is making them so confident? He also said that it's likely to become a Category 4 tropical cyclone, possibly even Category 5?!?

[Tornado Tim]

I just saw a headline on WeatherWatch's page saying "Cyclone heading for NZ" and then in his video he said 60% confidence of a direct hit. But then I saw a Stuff article where someone from MetService said basically what you guys are saying - that it's one to watch but too early to make a call. What does WeatherWatch have that no one else does that is making them so confident? He also said that it's likely to become a Category 4 tropical cyclone, possibly even Category 5?!?

Its because he is taking GFS as fact for some reason, which is the worst thing you can do. Multiple models need to be consulted. As David said GFS probabilistic is the only model progging this.
UKMO, CMC, ECMWF, JMA are all negative at this stage.

If EC probabilistic starts waning with the Ex-TC coming towards NZ then GFS should be given more weight.

But to me basing a forecast off one model alone is extremely foolish and indicates what league of forecasting is at play with that group.

[dizzy]

Thanks Tim. Sometimes it's obvious when it's just media hype, and when I look at the actual source it says something much less extreme. But in this case, it sounds like Weather Watch are the ones being sensationalist. He's probably just hoping to get lots of website clicks (whoops, I bought into it). Thanks a lot for clarifying.

[jamie]

Media take the image I have posted here and run with it. Its a real issue that needs addressing.

On the other hand, everyone on here would appreciate how rare a forecast like this is (hence I have put it up) but also how the odds are currently stacked against it for this to come off.

[dizzy]

I saw the same image on a Stuff article, but they quoted metvuw, so I expect they got it from the source. But metvuw is just un-edited GFS data isn't it? So no surprise that metvuw and Weather Watch agree.

[harleyb]

I see the UKMO 5-day model has backed off this one, sending it towards Fiji instead on their latest run. I bet we won't see that as an update on Stuff.

Personally I don't see the scenario picture above playing out, but if it does it would be catastrophic. Still a lot of disagreement in the models in the meantime however.

Was it last summer or the summer before when RSMC Nadi had a cyclone pegged at Cat 2 striking the North Island, despite plenty of evidence to the contrary?

[Manukau heads obs]

Still a lot of disagreement in the models

yes. which is why not a good idea to just rely on one model, as weatherwatch is currently doing

[Nev]

Might be worth noting that GFS was initially the least accurate of all the major models when it came to TC Victor's ultimate track.

Was it last summer or the summer before when RSMC Nadi had a cyclone pegged at Cat 2 striking the North Island, despite plenty of evidence to the contrary?

Dunno, but some forecasters got a little carried away with TC Pam last March. Remember this…

Karen Olsen charts cyclone Pam's progress.jpg

(Not to mention this track-map)

[treetop]

Regardless of the out come there is a huge amount of moisture coming our way from the NW/N and NE .I think the rain will be the problem not so much the wind.

[Manukau heads obs]

to be fair, TC Pam only needed to be a bit further west and it would have had a larger impact
I was in the Far eastern parts of the Coromandel that night and it was very windy with heavy rain

[Nev]

Yes, agreed. But it was Pam's category strengths I was alluding to rather than the actual path, i.e. Nadi had TC Pam at Cat 6 for a little while, then passing to the east of Gisborne as a Cat 4...

[Orion]

"... UKMO, CMC, ECMWF, JMA are all negative at this stage.

If EC probabilistic starts waning with the Ex-TC coming towards NZ then GFS should be given more weight...."

What does "CMC" and "EC" stand for, please?

(I wonder whether there could be an "Abbreviations Index" thread? 'twould save me looking 'em up.)

[Nev]

EC is just a shortening of ECMWF (European Centre for Medium-Range Weather Forecasts).

And CMC is the Canadian model (Canadian Meteorological Centre).

[harleyb]

Regardless of the out come there is a huge amount of moisture coming our way from the NW/N and NE .I think the rain will be the problem not so much the wind.

Yes, it sure looks that way. The earlier scenario of a deep ex-TC striking NZ is looking less likely now but there's also the possibility of a Tasman low coming in early-mid next week and then being supercharged by any tropical moisture coming down from the north, that in itself could be a significant event.

Either way, we wouldn't mind a decent dollop of rain around about now.... we're getting into the high 20s most days here and things are drying out rapidly.

[Manukau heads obs]

the only reason to even post images on the model outputs a week out when the lows are only just forming should only be for interest sake....
because they are just 'artistic license' at this stage and will flip flop every day...latest GFS has another possible outcome.....more in line with what you are saying harleyb

[Orion]

EC is just a shortening of ECMWF (European Centre for Medium-Range Weather Forecasts).

And CMC is the Canadian model (Canadian Meteorological Centre).

Thank you, Nev.
Shortening the abbreviation made it extra-tricky

[Tornado Tim]

If we look the situation more analytically, there are two systems at play here. Invest SH11 and Invest SH97.
Invest SH11 being given the main focal point at this stage.
Ensemble member output shows how the models is weighting tracks for the deterministic forecast:

Looking at the UKMO (White) and GFDL (Pink) (Geophysical Fluid Dynamic Labratory Model) - Operated by NOAA.
All model runs are on the 12Z cycle - 20160210 12Z

Screen Shot 2016-02-11 at 9.42.42 AM.png

For the UKMO Model:
You will only notice 1 ensemble member for Invest SH97 heading towards NZ (1 vs 25 members in total). and only 2 members for SH11 progging a NZ track.- 4% and 8% respectively.
Total: 12% Chance of effecting NZ.
For the GFDL Model:
Only one of 10 ensemble members for SH11 has a NZ Track. - 10% Probability
SH97 is still too far away as GFDL is shorter range model.
Total: 10% Chance of effecting NZ

Screen Shot 2016-02-11 at 10.13.31 AM.png

For GFS:
1 to 2 members of 25 total members for SH97 - 8% Probability
6 of 25 members for SH11 - 24% Probability
Total: 32% Chance of effecting NZ
ECMWF
The 12Z run is running late (so its not in this list yet).

Those odds for the Models are very low, even for the GFS!

[TonyT]

Good job tying that together Tim.

[Bradley]

Still so far out, even if we were 2 days out there would still be considerable uncertainty...interesting that Weather watch stated that Metservice "weigh heavily on ECMWF over GFS and ECMWF is certainly not predicting a direct hit - although a close call. We still have moderate confidence based on the fact there's still a fair bit of disagreement in the modelling". To say that's a confusing argument as to why they have a "moderate confidence" in a direct hit is strange to say the least!