Questions about 2003 Hurricane Season...

[Anonymous]

I have a few questions about the 2003 Hurricane Season and I thought you might be able to help me with them.

1. What caused Tropical Storm Bill's rapid new symmetric look as it made landfall and did Bill form an eye?

2. In the NHC's discussion on Claudette, they indicate that an eye was visible on July 10th. Is there an image out on the internet where you can see the eye?

3. What caused Hurricane Claudette to RAPIDLY strengthen to a borderline category 2?

4. What caused Hurricane Erika to turn south?

5. This one you may not be able to answer. Why did the official forecast never show Fabian strengthening rapidly when it was obvious favorable conditions were ahead?

6. Why did Grace weaken when the enviorment was generally favorable?

7. What caused Henri to speed up over Florida?

8. Why was Isabel uneffected by Fabian's cool wake?

9. If Isabel had not weakened, would she had been a category 5 at landfall, or how strong could she had been at landfall at the most?

10. Is there a possibility Hurricane Isabel was a borderline category 3 at landfall due to the damage?

11. Why didn't Juan weaken by landfall?

12. What are the chances Peter will be upgraded to a 75 mph-85 mph hurricane?

Thanks for any help you can give me. Merry Christmas!

[cycloneye]

#4=A strong high pressure inside the southern US made Erika turn west and later WSW and SW at landfall.

#8= Isabel was not affected by the fabians wake because those waters didn't cooled enough to make Isabel weaken.

#9=If Isabel would haved not weakened landfall would be as a cat 3 bordering a cat 4.

#12=Peter will probably be upgraded to a hurricane after post anaylisis.

Those are a few of my answers to some of the questions Floyd but I am sure that other members like for example Stormsfury,wxman57 and others will answer the rest of them.

[Anonymous]

Thanks, Luis.

[weatherluvr]

6. There was an ULL to the west of Grace that sheared her apart. (IMO, this would not have been classified had it not been so close to the coast.)

7. Similar to Grace, there was an ULL to the west of Henri that sheared it. It seemed to "speed up" as it went across the Florida peninsula, but it was more a case of the center relocating farther east as it made landfall.

10. Doubt it. Damage was consistent with a Cat 2, but the unusual landfall angle intensified the surge in some bays and inlets.

[Stormsfury]

1. What caused Tropical Storm Bill's rapid new symmetric look as it made landfall and did Bill form an eye?

Bill was sheared by upper-level southwesterly winds, and in fact, resembled more subtropical characteristics in its inception. As the center moved towards Louisiana, the ULL to its Southwest gradually moved away and sheared out, and at the same time, the center kept redeveloping, and translating ever so closer to the actual CDO type features ... as it made landfall, the system wasn't fighting as much shear, and actually looked better than it did during it's entire life cycle.

2. In the NHC's discussion on Claudette, they indicate that an eye was visible on July 10th. Is there an image out on the internet where you can see the eye?

Yes, and yes...



And a rapid scan movie available on my website 4.1 megs. (Hurricane Claudette QuickTime Movie) ... awesome ...

http://www1.msfc.nasa.gov/newsroom/came ... udette.mov

3. What caused Hurricane Claudette to RAPIDLY strengthen to a borderline category 2?

Shear dramatically lessened and allowed for the convection to fully wrap around the vigorous Low level center, and subsequentially strengthed.

4. What caused Hurricane Erika to turn south?

See cycloneye's answer ...

5. This one you may not be able to answer. Why did the official forecast never show Fabian strengthening rapidly when it was obvious favorable conditions were ahead?

They called for gradual strengthening ... rapid intensification parameters are very hard to gauge. Fabian did fight some wind shear and wasn't in hot bath water like SST's in its inception. However, the shear did decrease, and Fabian responded along with warmer SST's... In fact, Fabian may have crossed a warm eddy and a rapid intensification cycle began ... which are sometimes almost impossible to forecast at this time.

6. Why did Grace weaken when the enviorment was generally favorable?

Low TCHP (tropical cyclone heat potential) despite warm SST's, but Grace had multiple centers (or low-level eddies imbedded within a primary circulation which was also attached to a large trough), and thus could never consolidate properly ...

7. What caused Henri to speed up over Florida?

Good question. It was NOT expected to do so.

"HENRI ABRUPTLY ACCELERATED THIS MORNING AND MOVED INLAND NEAR TAMPA AROUND 9Z. THE CYCLONE IS CURRENTLY EMBEDDED IN A SMALL AREA OF RELATIVELY UNIFORM AND RAPID SOUTHWESTERLY FLOW BETWEEN A DEEP-LAYER ANTICYCLONE OVER CENTRAL CUBA AND THE MID-LEVEL TROUGH IN THE SOUTHEASTERN UNITED STATES. THIS ENHANCED SYNOPTIC GRADIENT WEAKENS MARKEDLY NORTH OF THE BAHAMAS SO THE CURRENT RAPID INITIAL MOTION...060/17...SHOULD BEGIN TO SLOW WITHIN THE NEXT 6-12 HOURS. THE 6Z GFS AND GFDL MODELS CAPTURED THE ACCELERATION OF HENRI. THESE TWO MODELS ARE IN GOOD AGREEMENT ON THE FUTURE TRACK OF THE
CYCLONE OVER THE NEXT 72 HOURS AND FORM THE BASIS FOR THE OFFICIAL FORECAST...WHICH CALLS FOR A SLOWING OF THE MOTION OVER THE NEXT THREE DAYS AS HIGH PRESSURE BUILDS TO THE NORTH OF HENRI."

8. Why was Isabel uneffected by Fabian's cool wake?

There was no cool wake for Isabel to be affected by. Not only that, the TCHP was quite high for that region, and Isabel had absolutely PERFECT conditions to thrive, as obviously noted with Isabel remaining a Cat 5 for a long time.

9. If Isabel had not weakened, would she had been a category 5 at landfall, or how strong could she had been at landfall at the most?

Two things happened here. First the remnants of Henri opened a weakness in the ridging in the SW ATL and Isabel found that weakness and took the path of least resistance ... secondly, westerly shear impinged on Isabel severely disrupting the perfect look of an annular hurricane. Otherwise, it is highly doubtful that Isabel would have been a CAT 5 for much longer anyways, due to 1) Eyewall Replacement Cycles, and 2) Conditions rarely remain PERFECT for maintaining intense hurricanes.

10. Is there a possibility Hurricane Isabel was a borderline category 3 at landfall due to the damage?

No. Although the wind fields ALOFT were quite impressive, Isabel was unable to sustain very deep convection around the center, as it had wrapped a lot of dry air within the circulation. However, spot microbursting occurred, and the synoptic setup induces sharp, strong, but very quick gusts that were much higher than the actual sustained winds as the convection that did exist was able to tap into the much stronger winds at flight-level.

11. Why didn't Juan weaken by landfall?

Two reasons ... 1) Rapid Movement towards Nova Scotia ... 2) Unusually warm SST's so far north ... about 3ºC warmer than normal as seen in this image ... and also a great comprehensive study from the Canadian Hurricane Centre ... (yes, the Canadian Hurricane Centre, and they do a pretty good job).

http://www.atl.ec.gc.ca/weather/hurrica ... ity_e.html

12. What are the chances Peter will be upgraded to a 75 mph-85 mph hurricane?

Very possible ... and even noted ny NHC officials. Post-analysis will probably upgrade Peter to a hurricane (but only for a six hour interval-one advisory) ..

SF

[Derek Ortt]

Some answers

1. Most strong tropical storms form an eye that is visible on radar. The eye starts to form around 50KT (as defined as a clear area surrounded by at least 50 percent of an eye wall). Satellite eyes typically arent visible until 75KT

2. Dont know as it is not important to the grand scheme of things

3. The shear relaxed and the dry air never wrapped into the center

4. Something called a strong ridge of high pressure. This is quite common for this region.

5. Because the official forecast never indicates rapid intensity changes except for landfall

6. It was a subtropical storm and conditions were not favorable

7. A trough

8. It may have been affected. It started to weaken as it crossed the path of Fabian. Isabel was very close to its maximum potential intensity, so even the 1 degree reduction would have a large impact

9. probably at least a 4 as it had maintained that for a long time. There would have bene nothing to cause the storm to weaken

10. Good glory no! No data supports sustained winds in excess of 91KT. it was intensifying as it made landfall, but didnt come close to cat 3

11. Fast motion and trough interaction

12. Maybe not. Tropical storms often have satellite eyes when they form underneath UL's as Peter did

[wxman57]

I have a few questions about the 2003 Hurricane Season and I thought you might be able to help me with them.

1. What caused Tropical Storm Bill's rapid new symmetric look as it made landfall and did Bill form an eye?

2. In the NHC's discussion on Claudette, they indicate that an eye was visible on July 10th. Is there an image out on the internet where you can see the eye?

3. What caused Hurricane Claudette to RAPIDLY strengthen to a borderline category 2?

4. What caused Hurricane Erika to turn south?

5. This one you may not be able to answer. Why did the official forecast never show Fabian strengthening rapidly when it was obvious favorable conditions were ahead?

6. Why did Grace weaken when the enviorment was generally favorable?

7. What caused Henri to speed up over Florida?

8. Why was Isabel uneffected by Fabian's cool wake?

9. If Isabel had not weakened, would she had been a category 5 at landfall, or how strong could she had been at landfall at the most?

10. Is there a possibility Hurricane Isabel was a borderline category 3 at landfall due to the damage?

11. Why didn't Juan weaken by landfall?

12. What are the chances Peter will be upgraded to a 75 mph-85 mph hurricane?

I'll try a few:

#1. Bill was not tropical in nature early in its life, and it was fighting some tough wind shear. Conditions aloft improved rapidly as it neared landfall, allowing for Bill to gain tropical characteristics and strengthen quickly. As for having an eye, that depends on what you call an eye. If you're talking about a visible, well-defined eye that you can see on satellite, well that feature generally doesn't appear until a storm's winds reach the 90-100 kt range. But all storms have an inner rain-free core to some degree, with squalls surrounding the core in a ring. I don't consider this to be an eye, however.

#2. SF answered this, but his image is NOT from the 10th of July, it's from the 15th of July. I have saved images of Claudette from the 10th and I'll see if I can post one in the next day or so.

#3. Agree with SF - shear decreased rapidly 12-18 hours prior to landfall. This resulted in very rapid strengthening.

#4. High pressure building north of Erika just prior to landfall drove it WSW into Mexico.

#5. Again, agree with SF. Very hard to predict rapid strengthening.

#6. The environment around Grace was extremely hostile - high wind shear. Grace was really a sharp tropical wave. There was no clear LLC at any time. The NHC jumped the gun BIG TIME because the system was near a populated area. I think they should do a post-season downgrade of Grace to a weak depression, if that.

#7. weatherluvr had a good answer here. Henri was very poorly-organized, and the speed-up was part increased mid to upper-level SW wind flow and a relocating center.

#8. The real reason here is that Isabel's track was several hundred miles NORTH of Fabians for most of the track. Only just north of the eastern Caribbean did Isabel cross Fabian's track briefly. And this was very near the same point where Fabian strengthened rapidly: http://weather.unisys.com/hurricane/atl ... index.html

#9. Easy answer - if Isabel hadn't weakened, it would have hit NC as a Cat 5. But perhaps your question really asked if Isabel hadn't weakened north of the Caribbean (well east of the U.S.) could conditions off the east U.S. coast have allowed Isabel to strike as a more powerful storm? I think the answer here is yes, but the question is really pointless as conditions obviously did not favor hanging on to a Cat 4 or 5 strength.

#10. Definitely not. Isabel was a borderline Cat 2 storm, not a borderline Cat 3. Damage was quite consistent with a strong Cat 1 to a very WEAK Cat 2. Folks along the NC coast haven't gone through the right front (stronger) quadrant of a hurricane in many decades. What they saw were true hurricane-force winds. Cat 3 winds would have destroyed about everything on the islands and caused a significantly higher storm surge. NC was VERY VERY lucky that Isabel was a relatively weak Cat 2.

#11. SF's answer is good. Warm SSTs and rapid movement prevented rapid weakening.

#12. I think the NHC would have done it by now, but it's possible. I'd rarther see Grace downgraded to a wave.

[Stormsfury]

Oops, didn't pay attention to that July 10th date on Claudette.

[caneflyer]

12. No chance.