Windspeed

Land interactions have certainly not been kind to Grace. But things can change pretty fast if a core does get established. Obviously the thermodynamic potential is out the roof tomorrow if it can get going.

Last pass found some 55kt flight level winds on the north side of the reorganized LLC. This is just off the coast of Jamaica. Let's see if Grace finally starts developing a core now despite its close proximity traversing near-to the northern shoreline of Jamaica today.

RE: Upper level pattern over the next 72 hrs: Watch as the upper ridge over the EGOM pivots and slides WSW while another upper ridge develops and follows Grace over the WCARIB and Yucatán. I've seen worse patterns for WCARIB hurricanes, including a couple of majors there last season. But we shall see...

Not really seeing a pronounced upper level trough or low feature. There is an upper ridge/anticyclone over the eastern to southeastern GOM that could impart some northeasterly flow over Grace in the NW Caribbean, but it is forecast to retrograde WSW. It's not terribly strong shear though as Grace will be moving in a western vector of motion with easterly mid-level steering flow. I'm not sure it would be strong enough shear to prevent strengthening at least to lower-end hurricane status by Yucatán landfall. That is if Grace can finally get its act together upon leaving Jamaica, which remains to be seen.

Appears the LLC has reorganized off the NE coast of Jamaica where the spiral band on SSIMS had suggested.

I do like the hurricane potential this weekend when Henri turns north towards the gulf stream. If timed right, it will be between two upper troughs with good thermodynamic support. Should be sufficient ventilation for a stronger hurricane as it heads into the maritimes by early next week.

Yeah, SSMIS really shows that banding organization well. If not for Jamaica, I would expect a core to form relatively quickly with such a strong spiral band curving into that center. But Jamaica likely will have some success slowing down that process at least until Grace has cleared the island to the west.

Curved banding structure is getting established. All Grace requires now is development of core banding, which may be within progress. Some disruption with a close pass of Jamaica may occur today, but I now also think Grace will become a hurricane prior to Yucatán landfall on Thursday.

Linda's structure right now is legit weather porn. Annular large eye with a very thin-radius CDO.

[emoji102]

A significant amount of rainfall has been occurring over the Tiburon Peninsula of Haiti this evening. Mudflows are going to be an issue throughout Tuesday and Wednesday. Moreover, the organization of Grace is not degrading but improving significantly tonight. This is going to be problematic for Jamaica over the next few days as well.

That position and intensity is pretty long range. Anything is possible at this point. I would be reluctant to focus on modeled intensity until we have a better understanding of what Grace is after it clears its interaction with the Tiburon Peninsula.

Latest from WPC...

Dennis is probably the most recent example of near-to path south of the Tiburon Peninsula that continued to intensify. Of course, Dennis was already a hurricane.

Just to jump off topic here, briefly, Josh was never in a reporting capacity for TWC. They reached out to him while he was on his regular chase schedule for several hurricanes. The WN gig was their decision to contract him for work and he took it. Fred was not a normal chase. Additionally, Josh now lives on the Gulf coast during hurricane season for this very reason. He has a particularly great skill set that can be advantageous for any particular network coverage. That being said, if there is an intense hurricane landfall, he's going to be in chase mode, not coverage mode. At any rate, no need to berate the man for getting paid. Speaking of...

As such over the past six hours, the vortex just can't seem hold onto convection long enough to close off a stable eyewall. One attempts to develop and then erodes. This is a telling sign that though shear is not too strong to prevent upshear convection within the vortex, it is still too strong to allow convection to not intermittently erode. Fred is running out of time here. Odds significantly decreasing this reaches minimal 'cane status. As is always typical with higher end Tropical Storms, heavy rain and flash flooding will be the main threat. But we could still see some strong gusts inland this evening.

You kid.. you kid.. But in all seriousness, this is a strengthening vortex versus a weakening major hurricane. We're watching for how convective organization evolves on the eastern side to get higher potential flight level hurricane force winds to mix down versus the western and southern flank of an eroding hurricane seen in years past.

Fred is trying. You can see where the LLC vorticity maximum is with the motion of light precipitation returns on the eastern side. Will that fill with strong convection into an eyewall?

Yes, might be a bit premature on a hurricane landfall. It's still possible but we need an eastern eyewall band/convection in the core of Fred to help mix down those flight level obs. There is a dry slot working into the eastern LLC right now. This may persist through landfall. There may be a few gusts near hurricane force in that eastern band outside the low level vort, but Fred is going to need to consolidate a real eastern eyewall before I am more confident in hurricane intensity.

Sorry for just now responding. The GFS has been more aggressive with totals from Fred over the Ridge and Valley and western side of the Blue Ridge. The SPC/WPC has the highest totals on the eastern side into the W. Carolinas. Euro is more in line with that, however some of this likely depends on how far west Fred's mid-level circulation pivots around the high and how strong Fred becomes prior to landfall. The GFS has been stronger than forecast and also keeps the heavier totals further west. We do need the rain but obviously not too much too fast and I hope I didn't seem like I was "model hugging". Here are the highest totals forecasted for Fred as of 3AM. Below is the latest GFS totals through 96 hrs as presumably Fred should be out of the region.

Yeah that's a wide swath of 4"+ totals for a large portion of the eastern valley and higher terrain. Most likely flooding is going to be an issue now.

Update to to upcoming weekly totals per Sunday 12z GFS:

Remote sensing information is showing a lot of landslides and ground deformation along the mountains of the Tiburon Peninsula of Haiti since the passage of Fred and the 7.2 magnitude EQ that occurred there yesterday. Regardless of Grace's classification, its wave envelope is still likely to produce significant flash flooding over the same region as Fred. This is concerning to say the least. Hopefully they can get folks out of mudflow prone areas where roads may be damaged prior to Grace's passage in the coming days. Upper level divergence will remain favorable for strong convection and prolonged heavy rainfall.

Deep convection is beginning to wrap upshear, north of the LLC.