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8/27/04 FCST: Frances (Atlantic)

A good indication of dry air in the area yesterday was the Miami observation of a dewpoint drop when some convection moved over (note the dewpoint fell to 68F from 77F after a shower). The convection appears to be wrapping more around the center of the storm based on radar, so perhaps there is still some window for strengthening. It still has 12-15 hours. Note that the AMX (Miami) radar is apparently not calibrated correctly (too "cold").

Based on a weaker hurricane, we are setting up one of the two SMART radars at Merritt Island airport, and the other at Space Coast airport. We're leaving the hotel shortly to begin ~24 hours of data collection. Good luck to all.
It really seems like the dry air intrusion would have a greater weight on the hurricane's weakening than the shear issue ... where did the shear come from? - It wasn't the ridge to the north at the time - it was still too far away to have an effect by the time the hurricane really started to putter ... and the soundings from Florida ahead of the storm showed completely unidirectional winds out of the east Wednesday night (I'm sure the plots are still around somewhere to take a look at). So either the shear was the result of some localized phenomena or maybe the UL winds were entering the storm from the SW because of another ridge on the other side of the storm?

Either that, or shear shouldn't be focused on as the primary factor for the storm's weakening and instead it should be the dry air as Kevin and several others have mentioned.

There is still the possibility that the storm will strengthen a bit as the current situtation shear tapers off. The question remains if dry air will continue to evaporate moisture ahead of the system or whether there will be juice as it sits in a favorable environment for development.
The latest VIS image from 0715 EDT is interesting in that it shows fairly strong convection to the W of the center, somewhat less strong convection to the E, and a narrow "wedge" of subsidence between the two. I don't know whether that's another eye trying to form, or just more dry air being sucked in, but there is cloud in that "wedge."

NHC's latest advisory now speaks of "large hurricane Frances" — apparently no longer dangerous.
I'm watching a radar loop right now and the "eye" hasn't budged an inch. It will be interesting to see what the TPC says at 11am.

Also, there is a clearing or lowering of cloud tops appearing within the eyewall...worth watching.
I'm at Merritt Island airport on a high speed internet connection. Sweet! Winds here have gusted as high as 60 kts so far. No water problems to speak of, and only a little rain. Looking at radar, it's only a short time before the fun begins.
The way she's reconstructing a distinct eye and becoming much more symmetrical, is upgrade to cat3 imminent?

[edit] From scanner: "Large blue crane about to fall at construction site"

What idiots left a crane standing??? Grrrrr
I think an upgrade is a real possibility. The biggest indicator is that the eyewall appears to be constricting.

A side not, there has always been an eye, it is appearing to be more substantial because the eye is getting closer to the radar site. Before there was only half an eye wall because the radar was looking above the other half.
Where is everybody? Let's get some more action on this site and the NOW thread.

YES...I am seeing ocean on the visible satellite in the eye!
"it is appearing to be more substantial because the eye is getting closer to the radar site. Before there was only half an eye wall because the radar was looking above the other half."

No, the southern end (which had limited convection) is closer to KAMX than the north side. You can clearly see on the loops that convection is filling in on the south side, which is nearer the radarsite.

- Rob
Gotcha...but I was referring to various sat imagery, but you're entirely correct. The way she's going, I wouldn't be surprised if we can see straight down to the sea on vis soon. That's very different from about the past 48 hours.
Very interesting that the eye is so large (about 70 miles wide). I've seen this with weak and strong circulations, but in my limited experience I can't recall this with moderate ones.

Also appears that there is a smaller eyewall (about 30 miles in diameter) but the radar returns are very weak there.

That inner eye wall is becoming better defined. It has almost run half way around the center. Should be intersting if that fills and completes the circle.
Several of the media I've watched this afternoon have also been commenting on the smaller area of tighter circulation (the eye within the eye) that may be tightening as convective areas become more intense along the northern eyewall. Would think this storm still has the potential to intensify slightly as it makes landfall -
It's interesting to watch this hurricane inch closer to land. Satellite presentation looks to be improving, though cloud-tops are warming on the southwest side of the 'cane, which is fits the observation of weaker echos on the southern side of the eye versus the northern side of the eye. A burst of convection / cooling cloudtops has been rotating around the northern side of the hurricane, so it'll be interesting to see what happens as it hits the weaker, SW side... Latest recon has shown 959mb central pressure, though I wouldn't be entirely surprised to see that slightly lower on the next update.

EDIT: I see a dropsonde observation from 2231z recorded a central pressure of 951mb, a rather signficant drop since the latest vortex message (from 2041z), which had 959mb. Mind you, there is a diff between hurricane hunter reported pressure and dropsonde pressure. LOL Of course this is all hinging on me reading/decoding dropsonde observations correctly...

EDIT II: The 8pm advisory did have 951mb central pressure, but a recent recon report showed only 960mb center. An update from NHC stated that the "new" central pressure is 957mb, so it's not deepening as quickly as previously thought.

This is a nice graphic of Frances' course. I don't know why they want to turn her to the north, she wants to go west. I am a little concerned for New Orleans because even though they project her course to turn North, she may wander more to the west before turning north. Each projection takes her a little more west than the last. It is the L over TX that is going to shunt her N? I have heard that the front is going to pick her up, but it is so far N or her. Is going to be interesting to see what she does when she reemerges in the Gulf.