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

[HURAKAN]

Interesting to see how the HWRF and GFDL disagree.

[cycloneye]

The big question is what will be left of Fred as the consensus of the models is after going north,then turns west.

[wxman57]

The big question is what will be left of Fred as the consensus of the models is after going north,then turns west.

Remnant swirl of clouds like the wave ahead of it? It's NOT heading for the Caribbean or the U.S.

[cycloneye]

12z UKMET tracks westward as a TD or minimal Tropical Storm.

http://moe.met.fsu.edu/cgi-bin/ukmtc2.c ... =Animation

[ozonepete]

Exactly. They now all move it north to 20N by Sunday morning as a TS, and then it turns northwest or west-northwest to 24N,43W by Tuesday morning as a remnant low. The reason for this is that the trough that's causing it to move northward right now is forecast to weaken and lift out by late Saturday or Sunday morning. Since Fred will be weak by then and thus a shallow low-level circulation only, it will be steered westward by the low-level trade winds. Since the HWRF and GFDL models forecast that Fred will still be fairly strong still on the weekend, they have its circulation still extending higher up into the atmosphere, where southerly winds will keep pushing it northward and shear and cooler water will kill it. The NHC is using a compromise between the different forecasts to come up with the track you see. Just remember that the weaker it gets the more west it will go.

As far as the latest runs, I haven't seen any new runs come out yet today, but they will be interesting because the trend has definitely been to move the track more westward.

And the most important thing to remember here is that there is some wicked shear (50-60 knots) just to its west and north, so no matter which way it goes it should get sheared to nothing. There is a small chance that the shear could ease up faster and that Fred makes it to 40W as a TS, but then more than likely another trough will get it next week. Still very interesting to watch. I'm enjoying watching it.

[ozonepete]

The big question is what will be left of Fred as the consensus of the models is after going north,then turns west.

Remnant swirl of clouds like the wave ahead of it? It's NOT heading for the Caribbean or the U.S.

Yeah, that's what it looks like alright.

[cycloneye]

12z NOGAPS also goes westward as a minimal Tropical Storm.

http://moe.met.fsu.edu/cgi-bin/ngptc2.c ... =Animation

[cycloneye]

000
WTNT42 KNHC 102038
TCDAT2
HURRICANE FRED DISCUSSION NUMBER 13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072009
500 PM AST THU SEP 10 2009

THE EYE HAS BEEN INTERMITTENT ON VISIBLE IMAGES AND THE CLOUD
PATTERN IS BECOMING ELONGATED DUE TO INCREASING SOUTHWESTERLY SHEAR.
CONVECTION IS STILL DEEP NEAR THE CENTER AND THE OUTFLOW IS MOSTLY
TO THE NORTH AND NORTHEAST. SATELLITE INTENSITY ESTIMATES INDICATE
THAT THE INITIAL INTENSITY HAS DECREASED TO 80 KNOTS BASED ON
LOWER DVORAK T-NUMBERS. MOST OF THE GLOBAL MODELS SHOW MASSIVE
UPPER-LEVEL SOUTHWESTERLY WINDS AFFECTING THE CYCLONE VERY
SOON. THESE WINDS ARE FUELED BY A STRONGER THAN NORMAL AND
PERSISTENT MID-OCEANIC UPPER-LEVEL TROUGH TO THE WEST OF FRED.
THIS UPPER-LEVEL PATTERN FAVORS WEAKENING...AND THIS PROCESS SHOULD
ACCELERATE DURING THE NEXT 24 HOURS OR SO. IN ABOUT 4 DAYS...FRED
SHOULD BECOME A REMNANT LOW.

FRED IS MOVING TOWARD THE NORTH AT ABOUT 4 TO 6 KNOTS...BUT SOON
STEERING CURRENTS ARE FORECAST TO COLLAPSE AND THE HURRICANE SHOULD
BECOME STATIONARY OR BEGIN TO MEANDER AROUND 19 DEGREES NORTH
DURING THE 2 OR 3 DAYS. THEREAFTER...GLOBAL MODELS DEVELOP A
SUBTROPICAL RIDGE TO THE NORTH OF THE CYCLONE...FORCING FRED OR ITS
REMNANTS TO MOVE TOWARD THE WEST-NORTHWEST. BY THEN...FRED WILL
PROBABLY BE A VERY WEAK SHALLOW CYCLONE STEERED BY THE LOW-LEVEL
TRADE WINDS. IN IS INTERESTING TO NOTE THAT MOST OF THE GUIDANCE
HAS CHANGED...AND NOW UNANIMOUSLY BEND THE TRACK WESTWARD. A COUPLE
OF DAYS AGO...SOME OF THE MOST RELIABLE MODELS INCLUDING THE ECMWF
TURNED FRED TOWARD THE NORTH-NORTHEAST TOWARD AFRICA OR EUROPE.

FORECAST POSITIONS AND MAX WINDS

INITIAL 10/2100Z 17.3N 35.1W 80 KT
12HR VT 11/0600Z 17.9N 35.2W 70 KT
24HR VT 11/1800Z 18.1N 35.2W 60 KT
36HR VT 12/0600Z 18.2N 35.2W 50 KT
48HR VT 12/1800Z 18.3N 35.2W 40 KT
72HR VT 13/1800Z 19.5N 36.0W 30 KT
96HR VT 14/1800Z 21.5N 39.5W 25 KT...REMNANT LOW
120HR VT 15/1800Z 22.5N 44.0W 20 KT...REMNANT LOW

$$
FORECASTER AVILA

[wxman57]

None of this really matters, it may go west for a while as a remnant low, but it's not coming within 1000 miles of land.

[ozonepete]

Here's where some of the reasoning for the steering forecast comes from for Fred at this point. The 1st image shows the current steering winds at 400-850mb, which are used for a storm of Fred's strength (975mb). You can see there basically aren't any, and Fred is stalling out. It will drift around almost in place for the next two days; maybe even do a loop. If it loops it will probably be a clockwise loop. By Saturday it will weaken to a TS, and so it will be shallow enough that the low-level steering winds will pick it up. The second diagram, the tropical model forecasts from (top to bottom) GFS, NAVY and CMC, show 850-700mb steering winds for shallow storms. Notice how the steering winds are west to southwest.

One interesting possibility is that Fred could remain a TS while it gets pulled west-southwest away from the shear and into warmer water again. That would be REALLY interesting. What are the odds of that? VERY VERY LOW. But I just wanted to point it out, because this is the fun in tropical forecasting: trying to guess all of the angles. And regardless, as I said earlier in this thread, the models are really terrible with stalled-out tropical cyclones, so it's even more fun to see them flail around with the data and show their limitations. It means they're not infallible yet (we already know that we're not).

[brunota2003]

Who said it "could come near land"? More time as a TS, regardless of fish or land, means more ACE

[cycloneye]

means more ACE

Bingo!

[Macrocane]

Who said it "could come near land"? More time as a TS, regardless of fish or land, means more ACE

The best thing we could have is an ACE maker with no threat to land

[cinlfla]

What is "ACE"?

tia

[expat2carib]

Wow....wow... ozonpete. You sound like a ninja warrior. I appreciate your opinions a lot. It looks like there is a lot of testosterone involved though'

Keep on going strong! I'm not sarcastic You will be a great forecaster one day. Take care of those hormones though. Things not always go that strong.

Regards

[cycloneye]

What is "ACE"?

tia

Here is an explanation of what ACE means.


http://en.wikipedia.org/wiki/Accumulate ... ual_storms

[ozonepete]

Wow....wow... ozonpete. You sound like a ninja warrior. I appreciate your opinions a lot. It looks like there is a lot of testosterone involved though'

Keep on going strong! I'm not sarcastic You will be a great forecaster one day. Take care of those hormones though. Things not always go that strong.

Regards

Thanks, expat. And don't worry. I know when to relax, and I know when to quit.

[Derek Ortt]

The GFS does show an upper anti-cyclone over the system as it nears the Islands and re-closes off a low there

However, I don't believe there will be anything left to close off then

[cycloneye]

00 UTC Best Track.

Still hanging on as a hurricane.

AL, 07, 2009091100, , BEST, 0, 172N, 351W, 75, 980, HU

ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/ ... 009.invest

[ozonepete]

Pretty sure it's going to do a small clockwise loop.