What is in Ivan's way

[CFLCaneWatcher]

to make the WNW NW turn? I am not knowledgable about this but I am sure others here can answer this. This looks to be an absolute monster if it continues to follow Charley's path. What will make make this increasing monster turn?

[Brent]

First the upper level low west of the system, but satellite imagery this evening shows it moving west so I'm not sure it's going to have any impact. Later in the period, a trough or a weakness in the ridge left by Frances would turn it, but it's too early to say if it will turn NE to Florida or simply NW into the Gulf.

[CFLCaneWatcher]

I anticipate the trough moving into the gulf by the weekend which will keep Ivan in the Eastern GOM, I am just having trouble seeing it get northerly enough from here to get to Western Cuba. It still continues to push hard West.

[B-Bear]

South America, if he doesn't turn.

[Weatherboy1]

The simplest way to explain the big-picture set up in 4-5 days (based on current models, forecast discussions, etc. -- they can always change) is this -- there will be a ridge somewhere in the western Gulf, a trough/weakness in the central/eastern Gulf/FL area and a ridge in the W Atlantic. Right now, a very strong ridge in the Atlantic with an extension poking into the FL area beneath Frances (which is slowly exiting to the N) is steering Ivan W/WNW. But as that pattern changes (the Atlantic ridge's Western extension gets eroded by that trough), Ivan should slow down and start hooking more WNW/NW. Beyond that, things get murky. If the trough digs further S into the Gulf, that WNW/NW motion will turn into a N motion ... and possibly even NNE motion a la Charley. The UKMET, ECMWF, GFS and NOGAPS models (as well as the latest GFDL run) all hint at some version of that scenario. The devil -- as always -- is in the details with a forecast 5-7 days out. When does Ivan start hooking more WNW/NW? Does that NW turn become a N move quickly? Or is the "slope" of the curve much more gradual? Or is the trough going to be weaker than all of these models are suggesting ... something that would allow the storm to stall, then eventually turn back WNW and head toward the central/western Gulf.

The simple answer is indeed simple -- it's too early to tell. My gut tells me this WILL NOT be an east coast FL/up the east coast US storm. I suspect it will be similar to Charley except further west ... say 100-200 miles with an eventual landfall in the NW FL area. But as a resident of Jupiter, FL who will be returning home tomorrow from CT, I plan to leave most of my shutters up until at least Thursday to see what the next two days of model runs show. By then, I'll have a much better idea what -- if any -- impact we'll see here.

Hope this helps...

[Ziplock48]

I am laboring under what might be an erroneous assumption, so here goes...read with caution, and take it with a grain of salt...

Since Northern Hemisphere storms are subject to the Beta effect, that is, they will naturally turn and head north, unless, of course, there is a feature...the High pressure ridge, which thwarts this poleward motion.

Since this is true, and since Beta is even stronger near the equator (opposite the Coriolis effect in terms of Latitude and strength), Ivan "wants" VERY badly to head north. A weakening of the ridge, or the ridge sliding out, will have the effect of allowing a move towards the North.

Is this correct?

A Trough of Low pressure (air rushes to fill low pressure) will "steer" the hurricane northward, when the trough (trof?) is to the west of the hurricane, since low pressure circulates counter clockwise. The flow on the EAST side of Low pressure is from South to North...and that is where you get the steering current. Ivan gets pushed North by any descending low pressure trof, and further gets a kick in the pants by the Beta effect...which has been acting on the storm all along, being almost balanced by the high which is pushing Ivan to the west. For newbies, air circulate clockwise around High pressure in the Northern Hemisphere, so on the SOuth side of a ridge or High pressure area, the flow is East to WEST.

OK so far?

I do think we will see Ivan start to turn more northward in the next 24 hours...and that turn should really set the board hoppin'. ANY weakness in the High that is steering Ivan should allow the turn. Now, wasn't that simple? I still have to rely on models, and especially on experienced forcasters on this board, whose interpretation of the models, helps my reasoning.

I am not sure how many samples, how much data is available in the low latitudes where Ivan is travelling. ??? Perhaps being so close to SA, there are enough buoys among other things for accurate sampling. Exactly HOW we know to expect the strengthening or weakening of ridges, other than looking at TRENDS, is still a mystery to me.

I would like to know...how DO forcasters "know" when a ridge is going to weaken or strengthen?

Hope the former helps some, and that the latter helps me learn!
Zip

[CFLCaneWatcher]

WOW! I asked a little and got a lot. Thanks for your answers. The trouble is they all make sense or they all make no sense. (No offence please) This thing could turn into any number of things. IMO, it will cross the Isle of Youth and pick up steam and land in the Tampa Bay area. God, I hope I'm wrong because I think these folks got spooked by Charley. Right now I just can't fathom it though as it looks like Ivan is heading WSW. It needs a lot of change to get on what I think is the proper course, WNW/NW. I guess time will tell.