Leslie Update # 3 .. Model Mayhem

Lets get into the heart of the matter... Tropical Storm Leslie.. What is going on with Leslie? We mentioned yesterdays update that this system was still not vertically stacked and this was just one of the reasons we thought development would be slower to occur. We also mentioned dry air as well as shear effecting the system. These three things have really not changed any..

1. We still do not have a vertically stacked system... Lets look at the 200,500, 700 mb vorticity charts..

You can see very clearly from the images at 06Z that we are still not vertically stacked. Matter of fact the mid level center is still discoupled from the lower level center. This is because the system is still under the influence of shear from the North.. While the shear over the system itself is not bad it is all being northerly directed and you can see the shear tendency map showing an increase around Leslie..

Only 5-10 knots across the southern part of Leslie but you can see 10-20 knots across the northern part and to the NW shear as high as 40 knots. This is something that you DO NOT want to see happen if you would like to see Leslie develop into a hurricane.

Just as last night the convergence and the divergence are actually decent across the system..

Now still yet another problem for Leslie to over come is the dry air that is also surrounding the system.

So at the present time what we need to see happen for strengthening of this system is as follows:
1. Dry air has to abate..
2. Shear has to decrease (most likely not with an Upper Level low moving off the east coast)
3. The system must become vertically stacked and pull the convection over top of the Center of circulation...

Looking at the guidance tonight does not really give a clear answer as to what is going to happen with Leslie...

You have the GFS (Global Forecasting System) which is so slow with the movement of the system that it takes to roughly 300 hrs for the system to be in the vicinity of Nova Scotia..

However..on the other side of the spectrum and a much weaker and progressive solution is the European Computer Model.. Now generally the ECM would reign supreme over the rest of the guidance but the model has been changing from run to run that there is not much consistency and the same thing can be said for the GFS. After all we just had both these major models not more then 24 hrs  ago have the Southern New England region in play..

Still yet there is the GGEM which is also a stronger system then what the ECM is showing.

Then perhaps another reason to give pause to the ECM with the weaker system would be the NOGAPS which is the most progressive model which is stronger and actually a touch slower then the ECM..

When you look at the wide view of the Atlantic you can really see the size of this system.

We are actually dealing with a very large system and it is hard to believe that the ECM is going to be correct with its weaker version that it is showing.
Though visible satellite really shows the effects of the shear across the NW part of the system ..

The water vapor image shows that the system is slowly strengthening...

The other thing that you can clearly see on the wide view water vapor is the upper level trough between the US and Bermuda. This upper level trough is going to essentially "cut off" and this upper level trough "should " create enough of a weakness in the ridge that Leslie should start going towards the NW...then eventually to the North..

Finally the steering currents that are in place and there is still ridging to the north of Leslie. So this means that Leslie should continue on a West to West Northwest path at least for the next 18-24 hrs ..it is at that point when the Upper level trough should form a cut off low and then allow Leslie to seek out that weakness.

Keep in mind that because of the shear size of this system it takes longer for these type of systems to become vertically stacked. Also while Leslie is getting close to a CAT 1 hurricane ..keep in mind that shear will be INCREASING due to the upper level trough (cut off low) from the NW

Until we can get an exact center location on Leslie..and with such radical swings being seen in the guidance , and increasing shear expected ... if Leslie does not become a Cat 1 in the next 12-24 hours she probably will not until after 96 hrs. 
With such uncertainty we are not going to be making a track at this point and time but we will continue to monitor the situation and our next update can be expected another 24 hours from now!