Matthew Analysis

[jeff]

Tropical storm heading for the US Gulf coast.

Adverse conditions are already affecting the coast with a large and extensive rain and wind field.

Track:

Guidance and NHC support a track toward the ENE then NE then N with a landfall over the FL panhandle near Destin.

Climatology supports a track more towards the east, while the steering pattern supports a track toward the NC or NE Gulf. An upper level low will be digging into TX over the next 24 hours and cutting off from the main jet. At the same time ridging will be maintained for the next 24-36 hours off the US east coast. This supports a steering flow as defined by NHC with a landfall in the region from Mobile AL to Panama City. However, it should not be discounted that the shearing SW winds will continue the deep convective bursts mainly E and NE of the center. It is very possible that the center could relocate eastward under this convection and result in a gradual shifting of the track to the east. Another possibility is that the shear relaxes a little and convection fires over the center. The threat here is a sooner poleward turn as the center would not be following the convection as much.

It was noted in the recon data that the mid and low level centers were not on top of each other, but tilted to the NE indicating the shearing. The last visible images showed a more elongated center and it is very possible that small vorticies are rotating around the broad center. I let the NHC track stand as I cannot go against the model clustering and the steering reasoning, however there is a threat to the FL west coast as well as west into SE LA. This system is not all that different from Josephine (1996), however the steering patterns are different and will likely result in the poleward trend suggested by NHC.

Intensity:

There has been a very deep convective burst this evneing very near or just ENE of the center. Water vapor still shows shear over Mexico and the west Gulf and this is forecast to remain. Given this, there will likley not be much intensification, unless the system speeds up to counter the shearing effects.

Regardless, strong winds are already affecting the Gulf coast from LA to FL as the PGF increases along the N Gulf. Tides are running above normal with coastal flooding a problem along the low lying SE LA coast. However, the main threat remains the excessive rainfall. There is an expansive area of rich tropical moisture pushing inland well ahead of the center with PWS at or above 2.0 inches. With the upper trough over TX, short waves are acting on this moisture to produce near continuous rainfall over LA and MS. As the center moves toward the coast, rainfall will continue to increase, becoming more concentrated and heavier in the convective burst ENE of the center. The flooding potential is high along and east of the track, especially over GA and Fl where rains from previous tropical systems have fallen.

It is not important to focus on the cneter as all the weather is east and northeast of the actual center. In fact if the shearing continues, the center may cross the coast as a convective free swirl of gusty winds. The worst of the weather will be well before landfall. If the shear does weaken some, and convection can fire around the center, then the system may be a more typical tropical cyclone with the strongest winds and heaviest rains near the center.

[JenyEliza]

The flooding potential is high along and east of the track, especially over GA and Fl where rains from previous tropical systems have fallen.

Well, just checked my local NWS site, and there is little mention of serious potential flooding. No SWS, nothing (as there is in Alabama). Seems we're going to go through denial up here (again). We always wait until the storm is almost over to decide it might be a problem afterall. Our schools do it, the local Mets do it, and to some extent Peachtree City does too.

Great.

Jeny

[Stormsfury]

A lot of uncertainties with this particular system in the MR with what continues to be a chaotic mess ... it's quite possible that Matthew will no longer be an identifiable tropical entity with the apparent separation of the LLC and MLC, but the diffluent shear steadily cutting across the system is preventing the storm from taking on a more classical TC structure while enhancing convergence around the MLC ... confluence and diffluence through all levels of the lower atmosphere will always yield an equavalent of zero ... you can't have all confluence or all diffluence thru the entire troposphere ...

BTW, jeff ... very good discussion