Global model runs discussion

[SapphireSea]

The ITCZ is being displaced way too far south for the wavetrain to help generate convection on the waves. This is also why the SAL is so prelevant at this point. Not that this is season cancel, not by a longshot. The powerful ridge and high pressures down in the atlantic is going to have to weaken some for the ITCZ to migrate to it's prime spot. Notice that when Chantel was getting going, the ITCZ was unusually far north and helped her get developed in the short term.

I always thought farther south meant better rotation? understand what you are saying but this wave does have a rather large moisture pouch.....it will come across the pond and maybe do something once in the carib...

Quite the opposite, the closer to the equator the harder it is to create rotation. There have been a small handful (I believe only one or two documented) of systems in the S WPAC that have been able to form at 0 latitude. I believe this is because vorticity has to do with the Coriolis effect in the MDRs, the equation changes towards low latitudes and becomes more difficult. Also, in the Atlantic generally anything under 5 degrees N is generally hostile with varying amounts of shear, on top of vortex inhibition. Carrib looks like it's pretty hostile right now in regards to shear as it usually always is at this time. Wave train looks great, it definitely will bear watching in a couple of weeks and into mid August, but the ITCZ needs to crawl up to help crank up convection near the waves. Look at the TWO maps for the ITCZ to be around 12-15N for prime time to start.

['CaneFreak]

Basically, I think what you are saying is correct but I just want to clarify that the equation doesn't really change in the lower latitudes; it's just that one part of the equation cancels out due to zero or near zero contribution. There is zero potential for a vortex to spin up at the equator due to the absence of the Coriolis effect at the equator. And in order for any cyclone to spin up, there must be at least some pre-existing vorticity to work with and at the equator, there is none.

Quite the opposite, the closer to the equator the harder it is to create rotation. There have been a small handful (I believe only one or two documented) of systems in the S WPAC that have been able to form at 0 latitude. I believe this is because vorticity has to do with the Coriolis effect in the MDRs, the equation changes towards low latitudes and becomes more difficult. Also, in the Atlantic generally anything under 5 degrees N is generally hostile with varying amounts of shear, on top of vortex inhibition. Carrib looks like it's pretty hostile right now in regards to shear as it usually always is at this time. Wave train looks great, it definitely will bear watching in a couple of weeks and into mid August, but the ITCZ needs to crawl up to help crank up convection near the waves. Look at the TWO maps for the ITCZ to be around 12-15N for prime time to start.

[Alyono]

Basically, I think what you are saying is correct but I just want to clarify that the equation doesn't really change in the lower latitudes; it's just that one part of the equation cancels out due to zero or near zero contribution. There is zero potential for a vortex to spin up at the equator due to the absence of the Coriolis effect at the equator. And in order for any cyclone to spin up, there must be at least some pre-existing vorticity to work with and at the equator, there is none.

Quite the opposite, the closer to the equator the harder it is to create rotation. There have been a small handful (I believe only one or two documented) of systems in the S WPAC that have been able to form at 0 latitude. I believe this is because vorticity has to do with the Coriolis effect in the MDRs, the equation changes towards low latitudes and becomes more difficult. Also, in the Atlantic generally anything under 5 degrees N is generally hostile with varying amounts of shear, on top of vortex inhibition. Carrib looks like it's pretty hostile right now in regards to shear as it usually always is at this time. Wave train looks great, it definitely will bear watching in a couple of weeks and into mid August, but the ITCZ needs to crawl up to help crank up convection near the waves. Look at the TWO maps for the ITCZ to be around 12-15N for prime time to start.

not accurate at all.

Coriolis is only ONE part of the vorticity equation. You also have the relative vorticity component. That is how the low latitude system have their COUNTER CLOCKWISE circulation extending south or the equator (see the development of Bopha last year... the outer part of its circ in its developing phase extended well south of the equator.

You simply need MORE relative vorticity near the equator to spin up a TC due to the lack of planetary vorticity

['CaneFreak]

This is probably a better way of explaining it. Thanks Alyono.

Back to the models...

not accurate at all.

Coriolis is only ONE part of the vorticity equation. You also have the relative vorticity component. That is how the low latitude system have their COUNTER CLOCKWISE circulation extending south or the equator (see the development of Bopha last year... the outer part of its circ in its developing phase extended well south of the equator.

You simply need MORE relative vorticity near the equator to spin up a TC due to the lack of planetary vorticity

[ROCK]

thanks Aly...

[Hurricaneman]

The 18zGFS starts developing something at 114 hrs at 8N 35W and from the wave about to come off of Africa and sends it north of due west and landfalls in Trinadad at 180hrs so we do have something of note coming off of Africa tonight if this is true

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[Rgv20]

The CMC still hinting about a possible TC in the Western Gulf in about 6 days, It looks like it develops from the Upper Level Low currently around 30-27N and 60W

12zCMC Day 6


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[ninel conde]

that high is rather far south. sitting right over the deep tropics. not good for development.

[CYCLONE MIKE]

Guess the cmc will eventually get one right as long as it keeps showing a storm or two hitting the gulf coast every week. Still reeling from the last two that hit here that the cmc nailed.

[cycloneye]

I would watch the late July/early August period for the models to start showing developments especially when the MJO returns to octans 1-2.

[blp]

I would watch the late July/early August period for the models to start showing developments especially when the MJO returns to octans 1-2.

Yes, the super longe range CFS is showing activity in this timeframe. I am looking more at the pattern and it continues to show strong High pressure and development in the MDR.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=noat&MODELL=cfs&MODELLTYP=1&BASE=-&VAR=pslv&HH=720&LOOP=1&ZOOM=0&ARCHIV=0&RES=0&WMO=

[cycloneye]

12z operational GFS has anything of significance until July 30. In two days the runs will end on August 1rst and from that time we will see if this model and others start to show developments.

[SouthFloridawx]

The 12Z GFS Run actually does show something like Luis mentioned albeit, in the long term.





It goes through a weakening phase, before ending up here. Looks like it could be rather large system. At that latitude, probably a fish, but hopefully a cool storm to watch.

[TheStormExpert]

It goes through a weakening phase, before ending up here. Looks like it could be rather large system. At that latitude, probably a fish, but hopefully a cool storm to watch.

Yeah but how can this be a fish storm and recurve with that ridging to the north and west?

[ninel conde]

its only a 1013 mb low. hardly a blip.

[Siker]

18z GFS has a storm at 240 hours near Cape Verde, it's way out there but it's something to look at because the GFS ensembles have been hinting at it for several runs.

[ninel conde]

its better developed than earlier.

[cycloneye]

A reminder about when posting graphics of models don't forget to download them with Imageshack or tinypic to preserve them.

[cycloneye]

GFS ensembles picking up activity on long range.

[WeatherEmperor]

It goes through a weakening phase, before ending up here. Looks like it could be rather large system. At that latitude, probably a fish, but hopefully a cool storm to watch.

Yeah but how can this be a fish storm and recurve with that ridging to the north and west?

The ridging you are speaking of appears to be at sea level pressure because the map you referenced shows MSLP...which I think is sea level pressure. Generally speaking, dont tropical cyclones get steered by the mean level flow...like at the 500mb level?

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