Tropical Cyclone Oma

[TonyT]

If that GFS run this morning verifies, it would be the most significant storm event in NZ recorded history and break the air pressure record. The 06Z run before it was even worse in some places. In my humble opinion, individual model runs for these types of cyclonic events should only be taken seriously under 100 hours but it sure is entertaining watching them

Yes it is entertaining watching them, I was looking at this run and thinking if this was 24 - 48 hours out then I'd be scoping out spots for a storm chase.

If you were 48 hours out from that you should be buying up food and water and nailing boards across your windows.

[Chris W]

This is one quite fascinating system, seems to be behaving differently to other TCs from my unlearned perspective.

[TonyT]

This is one quite fascinating system, seems to be behaving differently to other TCs from my unlearned perspective.

Current behaviour is fairly typical. Future behaviour yet to be determined as too many unknowns. Warm Tasman Sea and MJO phase 8 probably confusing model guidance at this time.

[Cyclone Tracy]

She's looking a little ugly at the moment. Forward motion has picked up a little, as she wobbles SW. The speed of her next 48 hours will most likely determine her longer term track. The trough in the Tasman will hold the exit door open for small window before the ridge builds and closes the exit door. This reminds me of the famous left hook on Hurricane Sandy off a ridge that launched her into the U.S east coast. Every model except EC missed it. Time will tell whether EC does it again or puts its tail between its legs and goes towards NZ.

The new EC 18z HD 3 day run is due between 1pm to 1.30pm NZT.

[Cyclone Tracy]

Deep convection developing in multiple quadrants, especially SE and SW. She’s starting to breathe again.

EC 18z run (3 day output only) has Oma around 150 to 200 km more SE than the 12Z run at 1am Friday morning (72 hours). Inconclusive on whether a SE turn is developing but definitely more SE on that run with a hint of a stronger trough.

[David]

JTWC forecast track has it down to 45 knots once it passes below 30' S latitude. Seems a bit on the low side?

[Thunder081]

Yes it is entertaining watching them, I was looking at this run and thinking if this was 24 - 48 hours out then I'd be scoping out spots for a storm chase.

If you were 48 hours out from that you should be buying up food and water and nailing boards across your windows.

Yeah yeah

[David]

Just for fun... Here's the most extreme GFS ensemble member currently. Please don't take it seriously

[TonyT]

Just for fun... Here's the most extreme GFS ensemble member currently. Please don't take it seriously

Interesting. Not taking it seriously in itself, but its existence indicates that something, somewhere in the atmosphere is spooking the GFS model into a totally unbelievable output. Something about the physics of the model itself is clearly getting trolled by something real in the current initialisation pattern.

[Bradley]

Just for fun... Here's the most extreme GFS ensemble member currently. Please don't take it seriously

Are the sea surface temp anomolies off the coast of NZ high enough to support a sub 950hpa beast at the moment hitting our shores?

[cbm]

I see some GFS runs now have it crossing the country but as the weakened remains of the TC, in the 980's hPA, and it not starting deepening again until it is clear of the mainland. In that scenario it'll be very significant but not beyond ex TC hits we have weathered several times in recent years. So yet another variable, even if it becomes locked into coming this way, we won't know how bad.

[cbm]

Just for fun... Here's the most extreme GFS ensemble member currently. Please don't take it seriously

Are the sea surface temp anomolies off the coast of NZ high enough to support a sub 950hpa beast at the moment hitting our shores?

Others understand this much better than me, but I think that model output is on the premise that it has already gone cold core and deepened rapidly by interacting with an upper trough. So don't need a warm sea at that stage. Warmer sea however will slow down how quickly it fills in while still warm cored as it leaves the tropics - which means there is more of it left/it's starting from a lower pressure when it gets the turbo boost.

[Ash]

Yeah latest Metvuw has a 950hpa beast just off the East Coast NI on Monday. It's been consistent with that last few runs.

[Cyclone Tracy]

Oma is currently attempting to build an inner eyewall. Lightning is also been detected within the inner SW and NW quadrant with deep convection now surrounding the inner core on sunset. Most of that dry air has been coughed out through the day. Still a cat 2 but she is certainly in better shape than first thing this morning. Also nice to see her appear on radar

I've been going over the 00z ensemble runs….still waiting for EC members to finish. Lots of drama past 96 hours across the board

[Cyclone Tracy]

She is still cruising SW at around 6 knots, winds have picked up to 60 knots and is at around 975 hPa, Cat 2.
The hostile environment is now behind her with favourable wind shear and SST’s around 27c. Still some dry air appearing near her core, holding intensification back.

Pure entertainment watching the models scramble on every run. The 4 ensembles have basically turned into junk due to wide spread across the 127 models. The good old strengthen ridge threatening the shut the exit door if she doesn’t hurry up and its forecaster’s nightmare. Aussies will be waking up this morning with 20 EC members attacking the Queensland Capricornia coast.

[David]

Most GFS ensemble members now showing similar to what EC has been showing for a while now, only a few members show it crossing NZ

[Cyclone Tracy]

Last 20 hours (to 9.15am) with microwave imagery of Oma gathering strength and attempting to create an eyewall.

[Cyclone Tracy]

JTWC latest cone of uncertainty has a tropical storm wind danger area that is approx. 2,200 km wide in 72 hours time . That has to be some sort of agency record for covering all based


I feel sorry for the ever is currently reviewing the ensemble tracks and has to draw the cone and arch.

[Cyclone Tracy]

EC 1802 18Z latest is locking onto a Queensland attack near Bundaberg on Saturday morning with a strong cat 2, possible cat 3. The EC control track goes the complete opposite direction to the latest JTWC track which is heading SE on the subtropical ridge. Access R is also joining in on the EC control path. The BoM uses the EC ensemble as their base for the TC tracks, so they will be all over this internally .... but this is TC Oma we are talking about

[Cyclone Tracy]

TC Oma has been reinstated as a severe cat 3 tropical cyclone by FMS at 2.57pm NZT. She has successfully reinstated an eyewall and is now showing the 'Donut of Destruction' symmetrical look. Not quite an annular tropical cyclone yet but her eye is much less ragged on the 3pm image.

[Cyclone Tracy]

Oma doing well. Around 970 hPa and falling, a solid cat 3 and will become a strong cat 3 within 24 hours with favourable conditions ahead. I've yet to see lightning around the inner eyewall but I'm watching her closely

This will be the most viewed BoM Automatic weather station for the next few days. Cato Island, currently sitting on 1002 hPa. http://www.bom.gov.au/products/IDQ60801 ... 4394.shtml


An ominous 00z run for SE Queensland. Both EC and the best U.S hurricane model HWRF are locking onto an area around Fraser Island, Queensland for a weekend landfall. Still over 100 hours out but if they are correct, Brisbane will get the nasty water bombing SW quadrant from the outer bands. EC going for 1 to 1.2 metres of rain. In 1974, Brisbane had a cyclonic hit from ex cyclone Wanda that devastated the city with flooding. Brisbane's population in 1974 was around 1 million, today its around 2.5 million. The BoM need to start preparing the public IMO.

[Cyclone Tracy]

Oma remains a cat 3 this morning, around 965 hPa, 75 knots winds, moving slowly SW.

Another dry air intrusion overnight around the eyewall has made her look asymmetrical this morning. Eye is quite ragged. She is currently trying to cough out that dry air and attempting to reform the eyewall. Sunrise allowing a glimpse of a ‘stadium effect’ on the western side of the eye.

The steering and her behaviour over the next 48 hours is fascinating. Models will be most likely be out of date as soon as they run. It’s all about observations and what she is doing real time to know what her next move is IMO.

[Cyclone Tracy]

Here is my 2 cents worth on the 2pm (NZT) observations.

- Eye is ragged and elongated with a semi eroded eyewall on the eastern side. Eye around 100km in length north to south.
- Low level circulation centre slightly further east north east than the latest model runs
-Travelling SW at 6 knots
- Winds 70 to 80 knots (Cat 3)
- Pressure 968 hPa
- Oma continues to battle with dry air into her structure, hindering further intensification at the moment.
-No lightning is evident within the storm.
-Deep convection continues to develop in the inner areas of each quadrant.

[Cyclone Tracy]

FMS re-classifies Oma back to a Cat 2 at 2.24pm NZT.

Latest Sat imagery at 2.50pm showing the eroding eastern side of the eyewall is regenerating itself. A sign she is trying to re-intensify again.

[Cyclone Tracy]

7pm satellite wind readings I’m getting from NOAA are around 70 knots, pressure mid 960’s. She is still a high end cat 2 bordering cat 3. BoM observation at Cato Island has dropped to around 1000 hPa and steady. Should drop into the low 990’s by tomorrow night. http://www.bom.gov.au/products/IDQ60801 ... 4394.shtml

And the model circus continues. Oma has them jumping at shadows on every run…. Fiji Met will be happy to hand this one over to the BoM asap