ATL: TROPICAL STORM BILL (03L)

[wxman57]

Wow, I guess maybe that northward jump wasn't just my imagination.

I don't think it's a northward jump so much as a relocation. The center wasn't easy to locate prior to sunrise. NHC had it too far south. But it is indicative of a more northward component.

[Emmett_Brown]

Well according to the ECMWF, that trough that turns Bill away from the US is reinforced by another trough a few days later --- which means East Coast threats could be shut down for quite sometime. It's still far out but that is some good news if it verifies.

Here is a link to see what I mean. It is at 240 hours:
http://www.ecmwf.int/products/forecasts ... 9081600!!/

Yes, given the data, there is little reason to doubt the model consensus. Amazing how quickly things have changed in the past 24-48 hours, models now missing the islands completely, and out to sea.

However, I feel like I have seen this before, only to see troughs set up further west, or not be as progressive. For that reason, it is something that islanders should watch. Even tightly clustered models have been known to change. Bill is still way out there...

[KWT]

Yeah its a sign that the surpression of the upper high that kept it heading WSW yesterday is now gone as the center relocated further northwards.

[KWT]

Actually your right to say the Atlantic Canada needs to watch this. The only two hurricanes in this position that recurved eventually went on to strike Newfoundland in the end....

[jconsor]

The UKMET is likely keeping this less vertically-stacked and more shallow than the other models, thus, allowing it to move more west. But we can see that is not the case, so that model can be disregarded at this time.

No, perhaps some of the other models are not vertically stacked and strong enough. The 00Z UKMET is stronger than the 00Z ECMWF and GFS for Bill for the next 2 days, at least in terms of 850 mb vorticity.

Also, check this out:

ATCF IDENTIFIER : AL032009
VERIFYING TIME POSITION STRENGTH TENDENCY
-------------- -------- -------- --------
00UTC 16.08.2009 11.1N 35.4W MODERATE
12UTC 16.08.2009 11.4N 39.2W MODERATE INTENSIFYING SLIGHTLY
00UTC 17.08.2009 11.8N 41.7W STRONG INTENSIFYING SLIGHTLY
12UTC 17.08.2009 12.9N 45.1W STRONG LITTLE CHANGE
00UTC 18.08.2009 13.7N 48.2W STRONG LITTLE CHANGE
12UTC 18.08.2009 14.4N 51.5W MODERATE WEAKENING SLIGHTLY
00UTC 19.08.2009 15.1N 54.8W MODERATE WEAKENING SLIGHTLY
12UTC 19.08.2009 16.0N 58.1W MODERATE LITTLE CHANGE
00UTC 20.08.2009 17.0N 61.0W MODERATE INTENSIFYING SLIGHTLY
12UTC 20.08.2009 17.8N 64.0W MODERATE LITTLE CHANGE
00UTC 21.08.2009 18.5N 67.2W STRONG INTENSIFYING SLIGHTLY
12UTC 21.08.2009 19.3N 69.5W STRONG INTENSIFYING SLIGHTLY
00UTC 22.08.2009 20.5N 72.3W STRONG LITTLE CHANGE

[cycloneye]

WTNT43 KNHC 161442
TCDAT3
TROPICAL STORM BILL DISCUSSION NUMBER 5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009
1100 AM AST SUN AUG 16 2009

BILL IS DISPLAYING A BEAUTIFUL CURVED BAND PATTERN ON SATELLITE
IMAGERY THIS MORNING WITH A NEW BURST OF CONVECTION OCCURRING NEAR
THE CENTER. A 0808 UTC QUIKSCAT PASS SHOWED MAXIMUM WINDS OF AT
LEAST 45 KT...AND DVORAK SATELLITE INTENSITY ESTIMATES ARE BETWEEN
45-55 KT. THE INITIAL INTENSITY IS SET TO 50 KT AS A BLEND OF THE
ABOVE DATA.

A SERIES OF MICROWAVE PASSES AND VISIBLE IMAGES HAVE CONFIRMED THAT
THE CENTER HAS SHIFTED A LITTLE BIT TO THE NORTH AND THE INITIAL
MOTION IS ABOUT 285/14. A CONTINUED WEST-NORTHWEST MOTION IS
EXPECTED FOR THE NEW FEW DAYS DUE TO SUBTROPICAL RIDGING TO THE
NORTH OF BILL. ALL OF THE GLOBAL MODELS BESIDES THE UKMET SHOW
THE TROPICAL CYCLONE MOVING TO THE NORTH OF THE LEEWARD ISLANDS AS A
BREAK IN THE RIDGE FORMS AT ABOUT 65W. MODEL GUIDANCE HAS SHIFTED
TO THE NORTHEAST THIS MORNING...AND THE OFFICIAL FORECAST FOLLOWS
THAT TREND.

ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE FOR CONTINUED
INTENSIFICATION DUE TO LIGHT SHEAR AND WARM WATERS. SSTS BEGIN TO
RISE MORE SIGNIFICANTLY IN A COUPLE OF DAYS AND THE NHC INTENSITY
FORECAST COULD BE CONSERVATIVE AFTER THAT TIME. ALL RELIABLE
GUIDANCE SHOWS THIS SYSTEM EVENTUALLY BECOMING A MAJOR HURRICANE...
THOUGH AT DIFFERING TIME PERIODS WITH THE STATISTICAL GUIDANCE
SHOWING IT HAPPENING EARLIER THAN THE DYNAMICAL MODELS. THE NHC
FORECAST IS RAISED FROM THE PREVIOUS ONE...AND IS IN GOOD AGREEMENT
WITH THE SHIPS/LGEM THROUGH 72 HOURS. THE INTENSITY FORECAST IS
LEVELED OFF AFTER 96 HOURS DUE THE POSSIBILITY OF WESTERLY SHEAR
DEVELOPING...AS SUGGESTED BY THE GFS/ECMWF MODELS.

THE QUIKSCAT PASS FROM THIS MORNING SHOWED THAT THE WIND FIELD WITH
BILL HAS EXPANDED...AND CONSEQUENTLY THE INITIAL 12 FT SEAS AND
FORECAST WIND RADII ARE LARGER THAN THE PREVIOUS FORECAST.


FORECAST POSITIONS AND MAX WINDS

INITIAL 16/1500Z 12.1N 38.4W 50 KT
12HR VT 17/0000Z 12.6N 40.4W 60 KT
24HR VT 17/1200Z 13.4N 43.1W 70 KT
36HR VT 18/0000Z 14.3N 45.9W 80 KT
48HR VT 18/1200Z 15.2N 48.6W 90 KT
72HR VT 19/1200Z 17.5N 54.0W 100 KT
96HR VT 20/1200Z 20.5N 59.0W 105 KT
120HR VT 21/1200Z 24.0N 63.5W 105 KT

$$
FORECASTER BLAKE

[Gustywind]

Well according to the ECMWF, that trough that turns Bill away from the US is reinforced by another trough a few days later --- which means East Coast threats could be shut down for quite sometime. It's still far out but that is some good news if it verifies.

Here is a link to see what I mean. It is at 240 hours:
http://www.ecmwf.int/products/forecasts ... 9081600!!/

Yes, given the data, there is little reason to doubt the model consensus. Amazing how quickly things have changed in the past 24-48 hours, models now missing the islands completely, and out to sea.

However, I feel like I have seen this before, only to see troughs set up further west, or not be as progressive. For that reason, it is something that islanders should watch. Even tightly clustered models have been known to change. Bill is still way out there...

Yeah you're right. Us in the islands don't let our the guard down, but for sure i love the fishing trend . If Bill is at 17N 50W... this time i will be happy to call it "FISHY BILL".

[shah8]

I found that quickscan near the end of yesterday's Jeff Master's blog post thread. Knowing just how idiotic people there can be, I know not be sure of the date or whatever...

[Windtalker1]

I may be the only one but I still like the UKMET. The UKMET calculates the vertical accelerations in the atmosphere rather than rely on the hydrostatic primitive equations. A weaker storm heads more West. I think Bill will remain weak until around the northern Leeward Island where then a more WNW motion will continue. He did not make a jog to the North but was just relocated to the North. Just my opinion.

[KWT]

Its not really weak now though is it, its at 50kts and strengthening from the looks of things.

Got a good structure to it as well I have to admit.

[Stephanie]

Well according to the ECMWF, that trough that turns Bill away from the US is reinforced by another trough a few days later --- which means East Coast threats could be shut down for quite sometime. It's still far out but that is some good news if it verifies.

Here is a link to see what I mean. It is at 240 hours:
http://www.ecmwf.int/products/forecasts ... 9081600!!/

It looks like it totally drops the high pressure in the Central Atlantic off of the loop before the turn.

It is still a long ways out and from what I remember is that there's always a couple of pendulum swings in a storm's direction before the middle is determined.

[alan1961]

one thing he does need to hang on to for as long as possible is the ITCZ moisture he's drawing in on the southern side, kept him good so far IMO.

[bob rulz]

I may be the only one but I still like the UKMET. The UKMET calculates the vertical accelerations in the atmosphere rather than rely on the hydrostatic primitive equations. A weaker storm heads more West. I think Bill will remain weak until around the northern Leeward Island where then a more WNW motion will continue. He did not make a jog to the North but was just relocated to the North. Just my opinion.

It's not weak though. It's at 50kt and strengthening at a pretty steady pace. It will easily get caught up in the weakness and pass north of the islands.

[KWT]

I think its got a big enough region of moisture Alan to not really need to worry too much over that. This has major hurricane written all over it IMO...

Also I'm far from convinced this isn't still a possible threat to New England for example but we shall see...

[capepoint]

Well according to the ECMWF, that trough that turns Bill away from the US is reinforced by another trough a few days later --- which means East Coast threats could be shut down for quite sometime. It's still far out but that is some good news if it verifies.

Here is a link to see what I mean. It is at 240 hours:
http://www.ecmwf.int/products/forecasts ... 9081600!!/

It looks like it totally drops the high pressure in the Central Atlantic off of the loop before the turn.

It is still a long ways out and from what I remember is that there's always a couple of pendulum swings in a storm's direction before the middle is determined.

Exactly. They will swing back westward later, then make a smaller right swing as they begin to settle down. Give it a couple more days and we should get a better idea of whats ahead.

[btangy]

Why stop with just a few model runs when you can have a whole army. Here's the probability of Bill passing within 150km of any given point as given by a combination of 4 of the major global ensembles run at 8/16/09 00Z totaling 112 members:



There's about <20% chance of Bill clipping the NE Lesser Antilles but more likely missing by a wide margin. Thereafter, the number of ensemble members going past 120 hours cuts off so the probabilities drop off a bit suddenly and the exact numbers aren't really meaningful, but the patterns still are. The primary cluster favors a recurve between 60-70W. There are still a few members hanging onto a path through the Bahamas, so there's still some uncertainty regarding the eventual evolution of the E coast trough. However, the trend of the ensembles has been moving more and more toward a recurve during the past few cycles supporting the consensus of the deterministic models (GFS,CMC,ECMWF) which the NHC is following.

[alan1961]

I tend to err on the slightly negative side KWT i know and just keeping in mind what has happened to Ana too, too many times we've had ideal conditions with storms that have gone poof, a full wrap around of that moisture envelope then i'll be happy

[Frank2]

Yes, given the data, there is little reason to doubt the model consensus. Amazing how quickly things have changed in the past 24-48 hours, models now missing the islands completely, and out to sea.

That's the reason why the fear being generated on Friday (even by the NWS SJU WSFO) was irritating, considering how quickly things can change - the EC trough has been forecast since last week, and as others have said it's forecast to be reinforced by another, so that really changes things from yesterdays "WNW to Florida" model tracks...

Frank

[jinftl]

Thanks for posting. Very interesting graphic....what it shows is that all solutions are based on probability. Nothing can be ruled out completely....but clearly there is short-term agreement. It will be valuable to follow the trend of this graphic as new models runs come out. Where can this graphic be found?

Why stop with just a few model runs when you can have a whole army. Here's the probability of Bill passing within 150km of any given point as given by a combination of 4 of the major global ensembles run at 8/16/09 00Z totaling 112 members:



There's about <20% chance of Bill clipping the NE Lesser Antilles but more likely missing by a wide margin. Thereafter, the number of ensemble members going past 120 hours cuts off so the probabilities drop off a bit suddenly and the exact numbers aren't really meaningful, but the patterns still are. The primary cluster favors a recurve between 60-70W. There are still a few members hanging onto a path through the Bahamas, so there's still some uncertainty regarding the eventual evolution of the E coast trough. However, the trend of the ensembles has been moving more and more toward a recurve during the past few cycles supporting the consensus of the deterministic models (GFS,CMC,ECMWF) which the NHC is following.

[KWT]

Seems like the highest confidence path is one that takes it rather close to Bermuda based on those ensembles. Still we will just have to wait and see.

12z GFS coming out now by the way.