Tropical Storm Bertha Model Runs

[Ivanhater]

12z UKMET...starts to turn towards the west at the end of the run as the trough flattens out...

[Frank2]

Perhaps Derek or one of the other meteorologists can answer this, but, Bertha might be less prone to wobbling, since a tropical storm produces less torque than a hurricane...

[KWT]

All have a very southerly track, must be missing the trough diving down I suppose thanks to the lower resolution. Some very curious tracks in there.

i keep seeing people say do to the low res.... however, have i not herd that the ensambles usually do better than the operational gfs?? basically because it takes in to consideration all possible scenarios and comes up with the most plausable out come... just a question..

It can do it just depends on each seperate set-up. By the way just because it may have less resolution that may not be a bad thing, as I've said before the GFS can have a bit of a bias when it comes to over-digging upper troghs outside of 72hrs.

[gatorcane]

06z GFS Esembles..odd

Big change in these model runs here. But being 5 days out it doesn't surprise me that
they are wobbling back and forth between curve and no recurve.

Let's see if these models trends of a bend west continue.

[Derek Ortt]

not sure about that Frank. I have never heard of that

[Frank2]

If I recall correctly, the late Dr. Burpee might have mentioned that in one of his manuscripts...

[Aric Dunn]

Perhaps Derek or one of the other meteorologists can answer this, but, Bertha might be less prone to wobbling, since a tropical storm produces less torque than a hurricane...

are you talking about the "angular Momentum" to determine the potential strength of a system.

well to answer your question simply and as a physics major.. think of a top you spin it really fast and it is stable for a time until drag and other outside forces start acting on it right. at that point it begins to wobble as it Spins Down. now take that same top and spin it slower. what happens?

[cycloneye]

Once again UKMET has a weak Bertha and continues to be the outlier.Here is the 12z UKMET text.


GLOBAL MODEL DATA TIME 12UTC 06.07.2008



TROPICAL STORM BERTHA ANALYSED POSITION : 17.4N 44.2W



ATCF IDENTIFIER : AL022008



VERIFYING TIME POSITION STRENGTH TENDENCY

-------------- -------- -------- --------

12UTC 06.07.2008 17.4N 44.2W MODERATE

00UTC 07.07.2008 17.8N 47.1W WEAK WEAKENING SLIGHTLY

12UTC 07.07.2008 18.5N 50.0W MODERATE LITTLE CHANGE

00UTC 08.07.2008 18.9N 51.9W WEAK WEAKENING SLIGHTLY

12UTC 08.07.2008 19.0N 54.2W WEAK WEAKENING SLIGHTLY

00UTC 09.07.2008 19.4N 55.6W WEAK WEAKENING SLIGHTLY

12UTC 09.07.2008 20.3N 57.7W WEAK LITTLE CHANGE

00UTC 10.07.2008 BELOW TROPICAL STORM STRENGTH

[MiamiensisWx]

I'm undoubtedly going to open a can of worms, but the GFS ensembles have performed better in regards to Bertha's movement over the past few days. They have consistently depicted a more westward movement, and their forecasts for Bertha's intensity have been more realistic and accurate. For instance, some of the GFS ensembles have correctly initialized a weaker Bertha with a faster forward movement, which corrobates nicely with observed data.

In some respects, the ensembles have slightly surpassed the operational GFS.

[Aric Dunn]

I'm undoubtedly going to open a can of worms, but the GFS ensembles have performed better in regards to Bertha's movement over the past few days. They have consistently depicted a more westward movement, and their forecasts for Bertha's intensity have been more realistic and accurate. For instance, some of the GFS ensembles have correctly initialized a weaker Bertha with a faster forward movement, which corrobates nicely with observed data.

I agree

[cycloneye]

12z GFDL goes north at around 61w:

WHXX04 KWBC 061728
CHGQLM
ATTENTION...NATIONAL HURRICANE CENTER

NCEP COUPLED GFDL HURRICANE MODEL FORECAST MADE FOR

TROPICAL STORM BERTHA 02L

INITIAL TIME 12Z JUL 6

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 17.2 44.4 275./18.0
6 17.7 46.2 286./18.6
12 18.2 47.9 286./16.5
18 18.6 49.5 286./15.8
24 19.3 50.8 298./13.9
30 19.6 52.1 284./13.0
36 20.1 53.1 296./10.0
42 20.8 53.7 316./ 8.6
48 21.3 54.8 295./11.3
54 21.9 55.9 297./12.4
60 22.2 56.8 293./ 8.5
66 22.9 57.6 311./10.4
72 23.6 58.4 312./10.3
78 24.6 59.4 313./12.8
84 25.4 60.0 326./10.0
90 26.3 60.6 322./10.5
96 27.2 61.0 337./ 9.7
102 28.1 61.3 341./ 9.2
108 28.8 61.5 350./ 7.0
114 29.5 61.6 350./ 7.1
120 30.0 61.6 358./ 6.0
126 30.6 61.4 19./ 5.3

[Aric Dunn]

Perhaps Derek or one of the other meteorologists can answer this, but, Bertha might be less prone to wobbling, since a tropical storm produces less torque than a hurricane...

are you talking about the "angular Momentum" to determine the potential strength of a system.

well to answer your question simply and as a physics major.. think of a top you spin it really fast and it is stable for a time until drag and other outside forces start acting on it right. at that point it begins to wobble as it Spins Down. now take that same top and spin it slower. what happens?

Anyway. the wobbling in both cases occurs but i Imagine the wobbleing in the tropical storm is not noticeable as much as a hurricane with a well defined eye.

[vacanechaser]

I'm undoubtedly going to open a can of worms, but the GFS ensembles have performed better in regards to Bertha's movement over the past few days. They have consistently depicted a more westward movement, and their forecasts for Bertha's intensity have been more realistic and accurate. For instance, some of the GFS ensembles have correctly initialized a weaker Bertha with a faster forward movement, which corrobates nicely with observed data.

I agree

i second that.... that was my point above... the ensambles seem to come out on top a lot due to all the variables that are taken into consideration and then they come out with the solution...


Jesse V. Bass III
http://www.vastormphoto.com
Hurricane Intercept Research Team

[KWT]

Hmmm GFDL still has a sharp recurve but then again it does move it to the NW by 72hrs which seems to be quite agressive I have to admit, we shall see. UKMO may be too far south but who knows, its still going westwards so we have to wait and see.
Ensembles have indeed done quite well under this set-up, the op has probably suffered from over-egging the strength and also over-doing the upper trough a little.

[Frank2]

Frank2 wrote:
Perhaps Derek or one of the other meteorologists can answer this, but, Bertha might be less prone to wobbling, since a tropical storm produces less torque than a hurricane...

are you talking about the "angular momentum" to determine the potential strength of a system.

well to answer your question simply and as a physics major.. think of a top you spin it really fast and it is stable for a time until drag and other outside forces start acting on it right. at that point it begins to wobble as it Spins Down. now take that same top and spin it slower. what happens?

I'm trying to envision that - the last time I spun a top was in 1967!

LOL

P.S. I'd say that a slow top would wobble more, so, that would mean Bertha would wobble more since it's axis is less defined than in a hurricane, but, perhaps I'm thinking of another law of physics when it comes to why major hurricanes wobble...

P.P.S. Didn't mean to get off-topic, folks...

[Aric Dunn]

what is still baffling to me is that the nhc has had a wnw track but keeps saying it supposed to head west for the next day or so ... bertha continues to be south of there forecast points.

[Aric Dunn]

Frank2 wrote:
Perhaps Derek or one of the other meteorologists can answer this, but, Bertha might be less prone to wobbling, since a tropical storm produces less torque than a hurricane...

are you talking about the "angular momentum" to determine the potential strength of a system.

well to answer your question simply and as a physics major.. think of a top you spin it really fast and it is stable for a time until drag and other outside forces start acting on it right. at that point it begins to wobble as it Spins Down. now take that same top and spin it slower. what happens?

I'm trying to envision that - the last time I spun a top was in 1967!

LOL

P.S. I'd say that a slow top would wobble more, so, that would mean Bertha would wobble more since it's axis is less defined than in a hurricane, but, perhaps I'm thinking of another law of physics when it comes to why major hurricanes wobble...

P.P.S. Didn't mean to get off-topic, folks...

thats not off topic did you see the other reply i posted..

[Aric Dunn]

funny thing all the models show that bertha should be moving wnw right now but well she not and it probably wont till about 60 w or

[Frank2]

Ah - yes, sorry, I didn't scroll up enough - that makes sense, since a well defined eye is much easier to track than the cloud mass that's out there today...

Thanks...

P.S. This reminds me of when I'd ask Dr. Burpee a dumb question like that, and, he'd say, "Okay, Frank!", as his way of letting me know that I was drowning - he was good at his profession, for sure...

LOL

[Aric Dunn]

Ah - yes, sorry, I didn't scroll up enough - that makes sense, since a well defined eye is much easier to track than the cloud mass that's out there today...

Thanks...

P.S. This reminds me of when I'd ask Dr. Burpee a dumb question like that, and, he'd say, "Okay, Frank!", as his way of letting me know that I was drowning...

LOL

no question is a dumb question..