ATL: TROPICAL LOW ex-FRED (ex-07L)

[wxman57]

Last few frames of the vis are showing a more NW motion with Fred's swirl:

http://metofis.rsmas.miami.edu/~dortt/s ... 1_loop.gif

Looked that way to me, too, initially, so I opened up GARP to measure the latest movement. I believe that apparent NW motion is an illusion caused by changing convective patterns. I put my cursor over the center on the high-res shot at 1745Z and advanced to the 1845Z shot. I measure 278 degrees at 9.5 kts.

[artist]

WHXX04 KWBC 181717

CHGQLM

ATTENTION...NATIONAL HURRICANE CENTER



NCEP COUPLED GFDL HURRICANE MODEL FORECAST MADE FOR



TROPICAL DEPRESSION FRED 07L



INITIAL TIME 12Z SEP 18



DISCLAIMER ... THIS INFORMATION IS PROVIDED AS GUIDANCE. IT

REQUIRES INTERPRETATION BY HURRICANE SPECIALISTS AND SHOULD

NOT BE CONSIDERED AS A FINAL PRODUCT. PLEASE SEE THE TPC/NHC

OFFICIAL FORECAST.





FORECAST STORM POSITION



HOUR LATITUDE LONGITUDE HEADING/SPEED(KT)



0 25.0 66.1 280./13.0

6 25.5 66.9 308./ 8.9

12 25.3 68.1 259./10.9

18 25.0 69.1 255./ 9.6

24 24.7 69.9 248./ 8.0

30 24.4 70.4 240./ 5.7

36 24.2 71.2 254./ 7.5

42 24.3 72.2 275./ 9.1

48 24.5 73.3 281./10.5

54 24.5 74.0 267./ 5.7

60 24.4 75.1 266./10.8

66 24.5 76.1 278./ 8.5

72 24.7 76.9 286./ 7.8

78 24.8 78.0 272./10.0

84 25.0 79.1 283./10.1

90 25.4 79.7 297./ 7.1

96 25.6 80.6 288./ 7.8

102 26.0 81.8 289./11.6

108 26.1 83.0 272./11.4

114 26.2 84.2 275./10.2

120 26.4 85.2 280./ 9.2

126 26.5 86.0 279./ 7.3






201

[Emmett_Brown]

Last few frames of the vis are showing a more NW motion with Fred's swirl:

http://metofis.rsmas.miami.edu/~dortt/s ... 1_loop.gif

Looked that way to me, too, initially, so I opened up GARP to measure the latest movement. I believe that apparent NW motion is an illusion caused by changing convective patterns. I put my cursor over the center on the high-res shot at 1745Z and advanced to the 1845Z shot. I measure 278 degrees at 9.5 kts.

Ok, thanks. I think you are right... must have been all that convection being stripped away that fooled my eye. 9.5 kts seemes like it has slowed a bit from yesterday. I dont think it can outrun the ULL to the E. Wx, do you think that ULL is going to weaken?

[artist]

low is too small to be resolved by QS

thanks Derek for that explanation. I didn't realize that could happen. You all help me learn something new every day!

[artist]

so at 3 eastern tomorrow?

[gatorcane]

Its not going to happen like this with Fred.... but you can see systems can ramp up quickly where ex-Fred is currently located. That Labor Day Hurricane below went to a CAT 5 (white segment is a CAT 5) in a matter of just a few of days:

[deltadog03]

Clouds are trying to thicken near the center. I wonder if we are about to see a burst of convection.

[gatorcane]

Dry air is no longer a problem:

[Aric Dunn]

hehe.. This is just hilarious..

you know something is perplexing when wxman57 starts making jokes .. lol

have to say that when people say tropical systems "act like they have a mind of their" that this system is the perfect example of that.

[deltadog03]

good point gator...Its about to get into much more moisture.

[Ivanhater]

According to the 12z GFS, it might have a bit of an anti-cyclone over it in the Bahamas.

[Aric Dunn]

Clouds are trying to thicken near the center. I wonder if we are about to see a burst of convection.

yeah it should continue to do that as there is quite a bit of convergence..

upper winds show relax a little tonight maybe under 20 kts, probably around 12 to 15kt.. which should allow for more convection especially if it some what maintaining in higher shear, lower should should help..

as for models i think they are all having a hard time resolving such a small system. So i think intensity forecast are all going to low until recon can measure the wind field

[Aric Dunn]

According to the 12z GFS, it might have a bit of an anti-cyclone over it in the Bahamas.

yeah a few pages back i posted a few images of this and the forecast for it.. gfs shows the ridge staying in place through the period but at 48 hours when Fred is nearing the bahamas the ridge is pretty much in the same location as it is now.

[Aric Dunn]

Dry air is no longer a problem:

good point gator...Its about to get into much more moisture.

well that image is mostly in the upper levels there is still some mid level dry air at the moment. but even that will soon fade as it heads more west..

this shows the dry air a little better.. it still has a little more to pass through but from this point on it should be slowly increases through the period.

[Aric Dunn]

here is a cool pic..
just realized those images were large...




http://www.nrlmry.navy.mil/tcdat/tc09/A ... .100pc.jpg

[boca]

I have a stupid question to ask. Ex Fred has been a swirl since 37w and the only reason why it hasn't developed is because of shear of 20 to 25mph. Now that the shear might drop off to possibly 15mph and the atmosphere is more moist after tonight why isn't the NHC calling for strengthening?

[Aric Dunn]

So since im on a posting spree here

latest mid and upper level winds map here which is related to the shear map...
showing the shear about to drop off pretty quickly over the next 12 to 24 hours as its right on the edge of the main streak of upper and mid level winds.

[Evil Jeremy]

I have a stupid question to ask. Ex Fred has been a swirl since 37w and the only reason why it hasn't developed is because of shear of 20 to 25mph. Now that the shear might drop off to possibly 15mph and the atmosphere is more moist after tonight why isn't the NHC calling for strengthening?

The NHC loves playing the conservative game. And still, the chances at redevelopment are still somewhat low.

[Aric Dunn]

I have a stupid question to ask. Ex Fred has been a swirl since 37w and the only reason why it hasn't developed is because of shear of 20 to 25mph. Now that the shear might drop off to possibly 15mph and the atmosphere is more moist after tonight why isn't the NHC calling for strengthening?

cause for simply that reason .. it should have dissipated a long time ago and in the past such system do not last very long without maintaing convection. I think they are doing the right thing giving the small system and shear at least for the next 12 to 24 hours. there are still uncertainties with how much shear will be over it which depends on how far north it goes ..

[boca]

Andrew was a swirl at some poimt then it bombed out east of the Bahamas.I look at Ex Fred and think what if this happens to Fred, bombing out in the Bahamas.I think all of us think that in back of our minds.