Good morning all,
The last 24 hours have revealed that Issac is a storm without a discernible core. The satellite imagery from Thursday evening showed several vorticity centers and no cohesive core. The mid level circulation is quite impressive and quite large.
Overnight the G-4 aircraft flew a mission over the Atlantic waters north of Hispaniola searching for the breadth of the subtropical ridge, while the P-3 NOAA Hurricane Hunter aircraft followed recently by the AF C-130 flew through the storm searching for the center of circulation.
The image above is the composite water vapor with visible image from CIMSS and the interesting thing is that the transverse banding is occurring in the western convective cluster. This is evident by the feather like high clouds moving out of the bright overcast. These clouds show the outflow channel in the mid and upper level of the storm and is an indication that Issac may be consolidating a bit. The initial position has been shifted southward again and is at 16.2 north, 69.6 west which puts it south of Santo Domingo.
The environment around the storm remains very hostile for development with highly sheared ares on the northwest and northeast periphery of the circulation.
The shear trends are still introducing higher shearing around the storm. So I certainly do not think the storm will have an easy time moving northward, due to this sheared environment, not to mention the mountains of eastern Cuba.
The last thing I will say this morning is that the initialization of the storm keeps moving south, the flights through the storm are having an extremely hard time finding the center of circulation, and the current track based on the past few days is showing a very distinct turn to the right. All on which is based on the models being clustered. So we will side with NHC for a weak tropical cyclone with plenty of moisture. Rain and wind are on the menu for the Keys, and the Islands of the Caribbean. Beyond that we need a definitive motion vector to emerge.
For arguments sake, which there has been a bit of this at my location overnight, if the storm moves northwest to north, and holds together enough to regain strength over the Gulf of Mexico, we may see the models have done a great job. Otherwise, if the storm remains on a more westward track, and passes over or near Jamaica, the forecast will change dramatically. With that being said, everyone along the Gulf Coast and Caribbean should be paying close attention to your local National Weather Service Office and the National Hurricane Center websites for official forecasts, watches, and warnings.