Examining the models

[Stormchaser16]

http://meteocentre.com/models/ecmwf_ame ... _0500.html

This is one HUGE trough especially for August. It is a trough the amplification of which I would expect in a mid winter pattern, but not in the beginning of August. What does it all mean?

http://meteocentre.com/models/ecmwf_ame ... _0500.html

As it begins to clear the coast, with a frontal boundary out ahead of it, shown by the HPC....

http://www.hpc.ncep.noaa.gov/medr/9kh.gif

It should begin to pick up Bonnie. But could Bonnie slip underneath this massive trough? Well I would find it very unlikely to do so. And there are a few reasons, number one being that its own strenghtening should help to have it gain more lattitude. And number 2 is Alex and the trough coming into the east now.

http://bricker.met.psu.edu/trop-cgi/avn ... =Animation

As Alex continues to cut NEwrd into the middle of the northern Atlantic, it will keep the western edge of the Bermuda high from building westward onto the east coast. And again, you will ask, well what affect does this have on Bonnie? You can see that the western edge should really be right north of PR, as Bonnie comes through the islands and likely begins to strengthen, the western edge of the HP will be less and less influential in terms of keeping Bonnie on a southerly track, it will begin to pull WNW around the edge of the high. As it does that, the front will begin to come through the east coast and will meet Bonnie. By the time that the front really begins to pull on Bonnie(turning it on a more NNW track or even beginning to recurve it) Bonnie will already be well placed probably somewhere near the eastern Bahamas. For this placement we need to look at the tropical models. For that I will post the link to the 18UTC models again...

http://files.hurricanealley.net/images/ ... LMDL01.gif

Pretty wide cone of possible tracks, however the general agreement is that within 3-4 days Bonnie should be somewhere near the eastern Bahamas. Once it gets there it should be in a relatively prime place for the oncoming front to take its effects on the system. But what happens then? lets go back to the EC....

http://meteocentre.com/models/ecmwf_ame ... _0500.html

It is interesting to note the rising heights behind the clearing trough, this is also shown on the other global models.

http://met.psu.edu/tropical/tcgengifs/

Animate any of the global models and they show the HP building back into the eastern US after the trough clears. The effects that this has on Bonnie could be quite interesting. Most likely if Bonnie is not too far gone when the HP builds back in, it may cause Bonnie to stall and possibly advance back to the west a bit. How far west it may actually go is not known at this point, however I would not personally expect it to come too close to the US, and there will probably be some that worry it will if indeed this does pan out. However go back to the EC and you will see the next s/w diving down into the northern tier of the US.

http://meteocentre.com/models/ecmwf_ame ... _0500.html

This should likely be the capping s/w for Bonnie and should send it on its final departure.

Let me run down a few points, some Im confident about, and some that there is some question on..... to create some topic of discussion here

Confidence:
-Bonnie will begin to take a more WNW track because of a retreating western edge of the Bermuda high
-A large trough will sweep into the eastern US days 4/5
-HP will build in behind this trough
-Bonnie will likely be affected by the frontal boundary as it comes through

What could go wrong?
-IF Bonnie doesnt develop at all, then the western edge of the high MAY be just enough to send it further west, where we will be in another cat and mouse nailbiting game of seeing if the frontal boundary actually comes to pick it up. The HPC has the front clearing down into Florida, s even if Bonnie heads more W and stays further S, the front should be vigorous enough to pick it on a more NW track
-If Bonnie does indeed have this occur, then when it is picked up by the front, and high pressure builds behind the trough, then the HP could become strong enough to pull it dangerously close to the eastern coastline
-The strength of the HP building in behind the trough is also a topic of concern now

All in all I am pretty confident that the trough will recurve Bonnie out to sea, though there may be one last hurrah of western movement as another HP comes in behind it, however the models show another s/w coming in which should be the final straw. There is less then a 5% chance in my mind of an east coast hit here folks.

[Stormchaser16]

-One more thing that I need to add, the further west this thing gets before curving WNW then the closer to the Eastern US it could come after the trough picks it up and HP builds back in. IF it gets west enough, one must also wonder, will a cold front really clear MIAMI in the beginning of August? Well the answer to that is probably, while its a rare occurance, it does seem like it is very possible ATT and once it does happen, expect it to take a definate toll on the track of Bonnie

[MWatkins]

Excellent, excellent analysis. Having a hard time finding something to argue about there. In fact I cant.

The only thing is that...perhaps...the trough does not get as deep as progged by the models...HPC discussion from today notes that the GFS has backed off a surface low further south (although it is in better agreement with the other models) associated with the big mama trough. This is a very outside shot...the models only need to get close to verifying to pick up bonnie.

Even if Bonnie does not develop the trough is deep and strong enough in the models to allow even a low-level system to gain some poleward ground.

FYI...there was at least 1 AVN ensemble member that took a weak vortex west for a long time...but hard to imagine that verifying.

MW

[Weatherboy1]

Great job talking about all the pieces on the board. We'll have to see how the game plays out over the next 48 hours -- I think a lot depends on the exact center of this system and how strong it gets.

One thing, though: As I mentioned in another post, I have lived in South FL all my life (with the exception of 4 years of college in Boston). I have never EVER seen a front make it all the way down here in August ... usually we get our first "cool blast" in October. But then again, there has to be a reason all these models are saying the same thing.

[USAwx1]

http://meteocentre.com/models/ecmwf_amer_12/PN_GZ_096_0500.html

This is one HUGE trough especially for August. It is a trough the amplification of which I would expect in a mid winter pattern, but not in the beginning of August. What does it all mean?

http://meteocentre.com/models/ecmwf_ame ... _0500.html

As it begins to clear the coast, with a frontal boundary out ahead of it, shown by the HPC....

http://www.hpc.ncep.noaa.gov/medr/9kh.gif

It should begin to pick up Bonnie. But could Bonnie slip underneath this massive trough? Well I would find it very unlikely to do so. And there are a few reasons, number one being that its own strenghtening should help to have it gain more lattitude. And number 2 is Alex and the trough coming into the east now.

http://bricker.met.psu.edu/trop-cgi/avn ... =Animation

As Alex continues to cut NEwrd into the middle of the northern Atlantic, it will keep the western edge of the Bermuda high from building westward onto the east coast. And again, you will ask, well what affect does this have on Bonnie? You can see that the western edge should really be right north of PR, as Bonnie comes through the islands and likely begins to strengthen, the western edge of the HP will be less and less influential in terms of keeping Bonnie on a southerly track, it will begin to pull WNW around the edge of the high. As it does that, the front will begin to come through the east coast and will meet Bonnie. By the time that the front really begins to pull on Bonnie(turning it on a more NNW track or even beginning to recurve it) Bonnie will already be well placed probably somewhere near the eastern Bahamas. For this placement we need to look at the tropical models. For that I will post the link to the 18UTC models again...

http://files.hurricanealley.net/images/ ... LMDL01.gif

Pretty wide cone of possible tracks, however the general agreement is that within 3-4 days Bonnie should be somewhere near the eastern Bahamas. Once it gets there it should be in a relatively prime place for the oncoming front to take its effects on the system. But what happens then? lets go back to the EC....

http://meteocentre.com/models/ecmwf_ame ... _0500.html

It is interesting to note the rising heights behind the clearing trough, this is also shown on the other global models.

http://met.psu.edu/tropical/tcgengifs/

Animate any of the global models and they show the HP building back into the eastern US after the trough clears. The effects that this has on Bonnie could be quite interesting. Most likely if Bonnie is not too far gone when the HP builds back in, it may cause Bonnie to stall and possibly advance back to the west a bit. How far west it may actually go is not known at this point, however I would not personally expect it to come too close to the US, and there will probably be some that worry it will if indeed this does pan out. However go back to the EC and you will see the next s/w diving down into the northern tier of the US.

http://meteocentre.com/models/ecmwf_ame ... _0500.html

This should likely be the capping s/w for Bonnie and should send it on its final departure.

Let me run down a few points, some Im confident about, and some that there is some question on..... to create some topic of discussion here

Confidence:
-Bonnie will begin to take a more WNW track because of a retreating western edge of the Bermuda high
-A large trough will sweep into the eastern US days 4/5
-HP will build in behind this trough
-Bonnie will likely be affected by the frontal boundary as it comes through

What could go wrong?
-IF Bonnie doesnt develop at all, then the western edge of the high MAY be just enough to send it further west, where we will be in another cat and mouse nailbiting game of seeing if the frontal boundary actually comes to pick it up. The HPC has the front clearing down into Florida, s even if Bonnie heads more W and stays further S, the front should be vigorous enough to pick it on a more NW track
-If Bonnie does indeed have this occur, then when it is picked up by the front, and high pressure builds behind the trough, then the HP could become strong enough to pull it dangerously close to the eastern coastline
-The strength of the HP building in behind the trough is also a topic of concern now

All in all I am pretty confident that the trough will recurve Bonnie out to sea, though there may be one last hurrah of western movement as another HP comes in behind it, however the models show another s/w coming in which should be the final straw. There is less then a 5% chance in my mind of an east coast hit here folks.

Awesome post. I have one thing to add. The GFS does not handle high amplitude patterns very well. This is mostly a winter problem however I have seen it occur several times during the Summer, especially beyond 240 hours. it's unclear exactly what the route of the bias may be---but it would be best to always check the GFS against the ECMWF.

[Stormchaser16]

Thanks for the kind words....

Yes Mwatkins- The trough may not be as deep as forecasted, however I tried to shy away from that idea because the EC is IMO an excellent MR model, and I would expect that if the trough were half as vigorous as it showed, that it would still have an affect on turning Bonnie northward.

Weatherboy- Yes, that is one thing I am very skeptical about, however as I mentioned, if Bonnie continues to get stronger overtime, then it will turn more towards the WNW and it should still be in a place where the front could carry it northward regardless if the front clears all the way down to Miami or not.

[Stormchaser16]

Indeed USA...... the GFS really should not be trusted in these situations, but it seems like its really the EC that wants to amplify that trough to such a great level, and then build the HP in afterwards..... interesting situation with the HP building in behind to say the least. And in that area and timeframe is where i expect the most error and trouble with forecasting to occur.

[caneman]

Thanks for the kind words....

Yes Mwatkins- The trough may not be as deep as forecasted, however I tried to shy away from that idea because the EC is IMO an excellent MR model, and I would expect that if the trough were half as vigorous as it showed, that it would still have an affect on turning Bonnie northward.

Weatherboy- Yes, that is one thing I am very skeptical about, however as I mentioned, if Bonnie continues to get stronger overtime, then it will turn more towards the WNW and it should still be in a place where the front could carry it northward regardless if the front clears all the way down to Miami or not.

This is what I'm having a hard time with as well. We had 2 fronts dip down here in July and when the first happened it was deemed as extremely rare so I guess that would make the 2nd one in July as just about unheard of. And now if we get one in August to come down to Central/South Florida wouldn't that be unbelievable. Certainly these rare events will have some type of affect on the seaon. I just hope doesn't come down at the right time to push a monster into West Florida.

[Stormchaser16]

Well if it does clear in this case, i would be inclined to say it would rather protect you from what could become a stronger Bonnie then cause you adverse conditions.

[caneman]

Well if it does clear in this case, i would be inclined to say it would rather protect you from what could become a stronger Bonnie then cause you adverse conditions.

Not Bonnie I'm worried about, it's the following ones.

[Stormchaser16]

O i know, i was just mentioning your luck in this case.

As for future storms, if a pattern like this continues, then it would be hard for the majority of storms not to turn out to sea.

[caneman]

O i know, i was just mentioning your luck in this case.

As for future storms, if a pattern like this continues, then it would be hard for the majority of storms not to turn out to sea.

Yep, seems like alot will turn away. However, for us with any October and Nov. activity in Caribb or Gulf they will get pushed our way.

[Stormchaser16]

Yes, unfortunately if something develops later on in the season in the GOM, a frontal boundary traversing the country would more then likely pull the storms back to Florida. However, the trade off could be worth it, as you would likely not be dealing with major Cape Verde Systems, but hopefully less intense GOM systems (not to say of course that GOM systems cant be intense) but, with frequent fronts coming through and so far south, it would seem that something developing in the GOM wouldnt have much time to fully develop without a front picking it up.

[USAwx1]

Indeed USA...... the GFS really should not be trusted in these situations, but it seems like its really the EC that wants to amplify that trough to such a great level, and then build the HP in afterwards..... interesting situation with the HP building in behind to say the least. And in that area and timeframe is where i expect the most error and trouble with forecasting to occur.

The GFS does the same thing with convective feedback over the Midwest during the summer (result of the model's paramaterization scheme), and has the tendency to over predict extratropical cyclogenesis in the Ohio vly and East coast during the winter due to lack of available data in the vicinity of specific features during initialization. Again all of this seems to be especially the case at longter ranges - Beyond day 10 (one of the reasons why the GFS develops those huge fantasy blizzards every other run). The UKMET Normally will handle phasing better, as well as the ECM, but beware b/c the EC LOVES to hold energy back in the SRN branch.

[Stormchaser16]

Yes, I remember that, during the winter, the EC had a huge tendency to hold back alot of energy from s/w's in the southern branch..... This caused me many long nights trying to figure out timing and phasing solutions on possible winter storms further upstream lol

[Aquawind]

Great thread Stormchaser16!! Thank You

[cycloneye]

This has been one of the best threads I haved seen in storm2k since october 2002 when it was created so Stormchaser16 congrats for posting it.

[ColdFront77]

It would be nice if I could post this sort of thing. Oh well.

Also, Luis... the professional meteorologist have posted similar posts as well as Mike (Stormsfury).

Well done, Stormchaser.

[Stormsfury]

Yes, I remember that, during the winter, the EC had a huge tendency to hold back alot of energy from s/w's in the southern branch..... This caused me many long nights trying to figure out timing and phasing solutions on possible winter storms further upstream lol

This past winter, it just wasn't the EC, it was ALL of the globals playing catch up ... three words ... SCREAMING PAC JET ...

SF

[Stormsfury]

Indeed USA...... the GFS really should not be trusted in these situations, but it seems like its really the EC that wants to amplify that trough to such a great level, and then build the HP in afterwards..... interesting situation with the HP building in behind to say the least. And in that area and timeframe is where i expect the most error and trouble with forecasting to occur.

The GFS does the same thing with convective feedback over the Midwest during the summer (result of the model's paramaterization scheme), and has the tendency to over predict extratropical cyclogenesis in the Ohio vly and East coast during the winter due to lack of available data in the vicinity of specific features during initialization. Again all of this seems to be especially the case at longter ranges - Beyond day 10 (one of the reasons why the GFS develops those huge fantasy blizzards every other run). The UKMET Normally will handle phasing better, as well as the ECM, but beware b/c the EC LOVES to hold energy back in the SRN branch.

The GFS ensembles aren't as severe with the EC trough on the medium average past day 6 after the first one lifts out ... (which is quite severe, even for the ensemble spread mean) ...

The Canadian Ensembles also indicate no significant threat as well ... only one member brings what could be Bonnie (TD #2) by this timeframe even remotely close to the Carolinas (and that's still a good three hundred miles away) ...

The NOGAPS ensemble mean is quite deep with the EC trough through Day 6/7 ... TD #2 would have to significantly slow and stay far enough south as to not be swept up should the progged trough be as deep as depicted ...

BTW, Awesome post, Stormchaser16.

SF