Dr. Jeff Masters' WunderBlog

Bill is gone; Invest 92 pops up

Posted by: Dr. Jeff Masters, 2:08 PM GMT on August 24, 2009

Hurricane Bill is no more. The hurricane swept past Canada's Nova Scotia province Sunday afternoon, then made landfall early this morning in southeastern Newfoundland as a borderline tropical storm/Category 1 hurricane. Bill's waves claimed two lives over the weekend, a 54-year old swimmer that drowned in Florida, and a 7-year old girl in Maine that got swept into the sea by a big wave. The first death of the 2009 Atlantic hurricane season occurred on August 16, when a swimmer drowned in the rough surf from Tropical Storm Claudette at Pananma City Beach, FL.

Nova Scotia misses a direct hit
The center of Bill scooted parallel to the coast of Nova Scotia Sunday afternoon, and never quite came onshore. Since the storm's forward speed was so rapid--about 35 mph--this resulted in a highly asymmetric wind distribution. Since the top winds of a hurricane include the forward motion of the storm, Bill's top winds of 85 mph observed in the offshore, right front quadrant of the storm meant that the winds on the weak side of the storm, over Nova Scotia, were 85 mph minus 35 mph, or just 50 mph. Winds along most of the coast stayed below 39 mph, the borderline for tropical storm-force winds. The strongest winds measured in Canada were at Sable Island, which lies 150 miles offshore of Nova Scotia. Winds on the island hit 61 mph, gusting to 77 mph, between 4 - 5 pm ADT Sunday afternoon. A few islands along the Nova Scotia coast, such as Beaver Island and Hart Island, reported sustained winds of 39 - 40 mph. The big story for Nova Scotia was the waves from Bill. Buoy 44258 at the mouth of Halifax Harbor recorded significant wave heights of 29.5 feet and maximum wave heights of 49 feet as Bill passed 50 miles offshore. The buoy recorded top sustained winds of 35 mph, gusting to 51 mph. The waves combined with a 1.5 - 3 foot storm surge flooded many coastal roads. Buoy 44150, about 160 miles offshore of of the southwest tip of Nova Scotia, was in the east eyewall of Bill between 10 - 11 am ADT, and reported sustained winds of 62 mph, gusting to 85 mph, with significant wave heights of 44 feet. The buoy recorded a maximum wave height of 87 feet, according to Environment Canada. The highest official rain report on Nova Scotia was 2.6" (65 mm) at Yarmouth. Rainfall cause some localized flooding and road damage. Bill's winds cut power to about 40,000 people at the height of the storm. At Peggys Cove, three men were hit by a giant wave but were not hurt. A gift shop and attached home in the village were swept off of their foundation.

Newfoundland gets hit, but damage is minor
The southeast corner of Newfoundland took a direct hit from Bill. The storm made landfall early this morning as a borderline tropical storm/Category 1 hurricane. Top winds on the island were measured at Cape Race, which recorded sustained winds of 58 mph, gusting to 76 mph, between 1:30 and 2:30 am NDT. A storm surge of 1.2 meters (4 feet) was estimated by Environment Canada for Placentia Bay where Bill made landfall. Damage was minor on Newfoundland, with no major flooding reported. Bill dumped up to three inches of rain on Newfoundland.

Figure 1. The eye of Hurricane Bill on August 19 at 2157 UTC, from a NOAA P-3 Hurricane Hunter aircraft flying at 10,000 feet. Photo credit: Jack Parrish of NOAA's Aircraft Operations Center.

Kelvin-Helmholtz instability waves in the eye of Bill
Flight Director Jack Parrish of NOAA's Aircraft Operations Center snapped a cool photo in the eye of Hurricane Bill on Friday, showing the existence of a Kelvin-Helmholtz instability wave (Figure 1). The photo was taken on August 19 at 2157 UTC, from a NOAA P-3 Hurricane Hunter aircraft flying at 10,000 feet. The photo is taken looking WNW towards the eyewall. The towering clouds of the eyewall extend up to 50,000 - 55,000 feet in the photo, and the ocean surface is not visible, due to stratocumulus clouds covering the bottom of the eye. The center of the photo shows that the top of one of these stratocumulus clouds has a feature that looks like a breaking wave in the ocean. Well, that is an example of a breaking wave in the atmosphere known as a Kelvin-Helmholtz instability wave. The atmosphere behaves as a fluid, and thus has wave-like motions. When there is a sudden change of wind speed along the top of a cloud (wind shear), the flow can become unstable and cause breaking waves to form. One can see Kelvin-Helmholtz in the sky several times per year, and several alert wunderphotographers have uploaded photos of these waves over the years. However, it is uncommon to see these waves in the stratocumulus clouds covering the eye of a hurricane.

Figure 2. Water vapor satellite image for 8:15 am EDT 8/24/09. A tropical wave is approaching the Northern Lesser Antilles Islands, but is running into high wind shear from an upper-level cold low to the west of it. Image credit: NOAA/SSD.

Tropical wave approaching Lesser Antilles becomes Invest 92
A tropical wave with a moderate amount of shower activity is moving west-northwest at 20 - 25 mph and is approaching the northern Lesser Antilles Islands. This wave was designated "Invest 92" (92L) by NHC this morning. The wave is under about 20 - 30 knots of wind shear due the strong upper-level winds from the west. These winds are being created by the counter-clockwise flow of air around an upper-level cold-cored low north of Puerto Rico (Figure 2). This low is expected to move west-southwest and slowly weaken over the next two days, allowing shear to drop to the moderate 10 - 20 knot range beginning Tuesday night, according to the SHIPS model. By Wednesday, the upper low is predicted to be weak enough and far enough away from 92L that it will have a chance to develop. Most of the models show some degree of development of 92L by Thursday, when it is expected to be a few hundred miles off the coast of South Carolina. This wave could turn northward and give a wet weekend to New England, though it is too early to be confident of this. NHC is giving 92L a low (less than 30% chance) of developing into a tropical depression by Wednesday morning. The upper-level low will create plenty of wind shear and dump cold, dry air into 92L over the next two days, so Wednesday is probably the earliest we can expect the system to begin organizing into a tropical depression.

Several models predict the development of a tropical wave coming off the coast of Africa late this week.

I'll have an update Tuesday.

Jeff Masters

Beach Wall wave 1 (BeachBecky)

Waves from Hurricane Bill crashing on the sea wall during high tide in Lynn, MA

Hurricane Bill Waves Day 2 # 9 (RIWXPhoto)

Kelvin-Helmholtz Instabilities (btangy)

Kelvin-Helmholtz Instabilities to the S of Boston. Wavy like pattern in clouds is caused by a difference in winds between the cloud layer and the layer just above (called wind shear). The manifestation of this at the top of the altostratus deck is quite a beautiful and rare sight!

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353. stormsurge39 5:57 PM GMT on August 24, 2009
Im confused, from what i see on this blog is that the SW Carrb looks and has better weather conditions for developement than 92L, but NHC didnt give it a yellow circle.

354. IKE 5:59 PM GMT on August 24, 2009
TROPICAL WEATHER OUTLOOK NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 200 PM EDT MON AUG 24 2009 FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO... DISORGANIZED SHOWERS AND THUNDERSTORMS A FEW HUNDRED MILES EAST OF THE LEEWARD ISLANDS CONTINUE IN ASSOCIATION WITH A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW. SOME SLOW DEVELOPMENT OF THIS SYSTEM IS POSSIBLE OVER THE NEXT COUPLE OF DAYS AS IT MOVES TOWARD THE WEST-NORTHWEST AT 20 TO 25 MPH. THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS. $$ FORECASTER KIMBERLAIN/PASCH Member Since: June 9, 2005 Posts: 23 Comments: 37044

355. cyclonekid 5:59 PM GMT on August 24, 2009
Quoting stormsurge39: Im confused, from what i see on this blog is that the SW Carrb looks and has better weather conditions for developement than 92L, but NHC didnt give it a yellow circle. Not yet. The 2pm TWO hasn't gotten out. Member Since: July 14, 2009 Posts: 51 Comments: 1629

356. hurricanemaniac123 5:59 PM GMT on August 24, 2009
I think we were all wrong. 000 ABNT20 KNHC 241757 TWOAT TROPICAL WEATHER OUTLOOK NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 200 PM EDT MON AUG 24 2009 FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO... DISORGANIZED SHOWERS AND THUNDERSTORMS A FEW HUNDRED MILES EAST OF THE LEEWARD ISLANDS CONTINUE IN ASSOCIATION WITH A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW. SOME SLOW DEVELOPMENT OF THIS SYSTEM IS POSSIBLE OVER THE NEXT COUPLE OF DAYS AS IT MOVES TOWARD THE WEST-NORTHWEST AT 20 TO 25 MPH. THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS. $$ FORECASTER KIMBERLAIN/PASCH Member Since: September 21, 2008 Posts: 9 Comments: 688

357. HurricaneKyle 5:59 PM GMT on August 24, 2009
ORANGE Alert for 92L. Member Since: August 10, 2009 Posts: 3 Comments: 672

359. HurricaneKing 6:00 PM GMT on August 24, 2009
000 ABNT20 KNHC 241757 TWOAT TROPICAL WEATHER OUTLOOK NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 200 PM EDT MON AUG 24 2009 FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO... DISORGANIZED SHOWERS AND THUNDERSTORMS A FEW HUNDRED MILES EAST OF THE LEEWARD ISLANDS CONTINUE IN ASSOCIATION WITH A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW. SOME SLOW DEVELOPMENT OF THIS SYSTEM IS POSSIBLE OVER THE NEXT COUPLE OF DAYS AS IT MOVES TOWARD THE WEST-NORTHWEST AT 20 TO 25 MPH. THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS. $$ FORECASTER KIMBERLAIN/PASCH Member Since: July 6, 2005 Posts: 71 Comments: 2430

360. cyclonekid 6:00 PM GMT on August 24, 2009
2PM TWO is out... will post both as soon as ATL TWO comes out. Member Since: July 14, 2009 Posts: 51 Comments: 1629

361. stormsurge39 6:00 PM GMT on August 24, 2009
Also,I saw SW Carrb disturbance could be influenced to be pulled NW?

363. atmoaggie 6:01 PM GMT on August 24, 2009
Quoting cyclonekid: 2PM TWO is out... will post both as soon as ATL TWO comes out. Oh good. I don't know where to get those. Member Since: August 16, 2007 Posts: 6 Comments: 12461

364. WxLogic 6:02 PM GMT on August 24, 2009
I guess NHC has more confidence than us that this one will develop... now with a medium shad (30 to 50%). I might say they are thinking that it might develop sooner than what I at least expect. Member Since: August 14, 2008 Posts: 4 Comments: 4667

365. cyclonekid 6:02 PM GMT on August 24, 2009
Huh? I thought it was orange. Member Since: July 14, 2009 Posts: 51 Comments: 1629

367. WxLogic 6:03 PM GMT on August 24, 2009
Quoting atmoaggie: Oh good. I don't know where to get those. LOL Member Since: August 14, 2008 Posts: 4 Comments: 4667

368. cyclonekid 6:03 PM GMT on August 24, 2009
Quoting atmoaggie: Oh good. I don't know where to get those. Oh...here's the link http://www.nhc.noaa.gov/index.shtml Member Since: July 14, 2009 Posts: 51 Comments: 1629

370. atmoaggie 6:03 PM GMT on August 24, 2009
Quoting cyclonekid: Oh...here's the link http://www.nhc.noaa.gov/index.shtml Thanks. Member Since: August 16, 2007 Posts: 6 Comments: 12461

373. HurricaneKyle 6:05 PM GMT on August 24, 2009
Quoting Vortex95: NHC messed up the two the discussion says 30-50 but the pic say >30%. Backwards. :p Its at orange. Member Since: August 10, 2009 Posts: 3 Comments: 672

374. hurricanehanna 6:05 PM GMT on August 24, 2009
Quoting atmoaggie: Oh good. I don't know where to get those. Why am I laughing so hard right now??? Member Since: September 5, 2007 Posts: 0 Comments: 3214

375. atmoaggie 6:05 PM GMT on August 24, 2009
Quoting Vortex95: NHC messed up the two the discussion says 30-50 but the pic say >30%. I am sure the pic will be updated soon...possibly while I post this. Member Since: August 16, 2007 Posts: 6 Comments: 12461

376. AllStar17 6:05 PM GMT on August 24, 2009
. Member Since: June 29, 2009 Posts: 13 Comments: 5135

377. TheCaneWhisperer 6:06 PM GMT on August 24, 2009
I don't think they are lazy, they just think people are going to give them more than 15 seconds to update the graphic.

378. IKE 6:06 PM GMT on August 24, 2009
Maybe this is the part the NHC screwed up on...THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ???? Either that or they are running low on orange crayons? Member Since: June 9, 2005 Posts: 23 Comments: 37044

379. Floodman 6:06 PM GMT on August 24, 2009
Quoting atmoaggie: Huh. I had an oma, too. From Dortmund. I actually have a piano that belonged to her parents and survived unscathed as the house collapsed around it due to the British bombing raids. aus Dortmund? Outstanding... Member Since: August 2, 2006 Posts: 10 Comments: 9919

380. TheSuperCane 6:06 PM GMT on August 24, 2009
Good evening everyone it´s my first post. I´m from Germany and interested in tropical storms and the impacts of them with europe. I think, if the shear, produced by the upper level low will decrease tomorrow, 92L will develope quite qickly. Sure the track is hard to predict at the moment, cause nobody knows, whre the LLC will devolope. (Sorry for my bad english) Greets

381. stormpetrol 6:07 PM GMT on August 24, 2009
If 92L is orange, I think the disturbance in SW Caribbean should go directly to orange or even red, jmo. Member Since: April 29, 2007 Posts: 0 Comments: 6400

382. HurricaneKyle 6:07 PM GMT on August 24, 2009
Quoting IKE: Maybe this is the part the NHC screwed up on...THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ???? Either that or they are running low on yellow crayons? If you look at the yellow circle on the TWO map, its the 8 AM discussion on it. Member Since: August 10, 2009 Posts: 3 Comments: 672

383. scottsvb 6:07 PM GMT on August 24, 2009
Well its defidently not a closed circulation yet @ the low levels.... weak low level vortex around 15.6N and 60.2W on close-up vis.... also midlevel circulation around 18.5N and 57.3W... Im still very skeptical of this thing making it all the way to a tropical system,... might be fighting some cold-core symptoms... maybe subtropical.... who knows of yet. Anyways a weaker non developed low will move more W or WNW with the LLF if its going to keep getting shared (as expected for the next 24-48hrs).... and btw we should of designated the area in the SW carribean as a TD and would probably be a TS in the next 12 -24hr before making landfall in Nicaragua... pressures are around 1006mb down there and a well defined LLC. Scottsvb Member Since: January 22, 2006 Posts: 0 Comments: 1065

384. TampaSpin 6:07 PM GMT on August 24, 2009
Quoting caneluver: It will be inland in a few hours! No since in waisting anyones time in putting a circle on the map! No worries at all just some bad thunderstorms, jee wizzzzz people exactly Member Since: September 2, 2007 Posts: 175 Comments: 19747

385. hurricanehanna 6:07 PM GMT on August 24, 2009
http://rds.yahoo.com/_ylt=A9G_bDjA1pJK2GwA872JzbkF;_ylu=X3oDMTBpdnJhMHUzBHBvcwMxBHNlYwNzcgR2dGlkAw--/ SIG=1hqdtjd2c/EXP=1251223616/http%3A//images.search.yahoo.com/images/view%3Fback=http%253A%252F%25 2Fimages.search.yahoo.com%252Fsearch%252Fimages%253Fp%253Dorange%252Bcrayon%2526ei%253DUTF-8%2526fr%2 53Dyie7c%2526fr2%253Dtab-web%26w=400%26h=322%26imgurl=www.wpclipart.com%252Feducation%252Fsupplies%2 52Fcrayons%252Fcrayon_orange.png%26rurl=http%253A%252F%252Fwww.wpclipart.com%252Feducation%252Fsuppl ies%252Fcrayons%26size=29k%26name=crayon%2Borange%2Bpn...%26p=orange%2Bcrayon%26oid=69977cf80b939b54 %26fr2=tab-web%26no=1%26tt=8830%26sigr=11javsk70%26sigi=11u4tabq0%26sigb=12q373n8m Member Since: September 5, 2007 Posts: 0 Comments:** 3214

387. nrtiwlnvragn 6:08 PM GMT on August 24, 2009
Quoting IKE: Maybe this is the part the NHC screwed up on...THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ???? Either that or they are running low on orange crayons? Quick, get out the red one, we can make it appear orangish. Member Since: September 23, 2005 Posts: 11 Comments: 8937

388. cyclonekid 6:11 PM GMT on August 24, 2009
Quoting TheSuperCane: Good evening everyone it´s my first post. I´m from Germany and interested in tropical storms and the impacts of them with europe. I think, if the shear, produced by the upper level low will decrease tomorrow, 92L will develope quite qickly. Sure the track is hard to predict at the moment, cause nobody knows, whre the LLC will devolope. (Sorry for my bad english) Greets Welcome to WU! Looks like you have Bill to worry about...well...maybe not. Member Since: July 14, 2009 Posts: 51 Comments: 1629

389. hurricanehanna 6:09 PM GMT on August 24, 2009
oh just ignore 385 - won't let me fix... moving along Member Since: September 5, 2007 Posts: 0 Comments: 3214

390. IKE 6:09 PM GMT on August 24, 2009
Quoting HurricaneKyle: If you look at the yellow circle on the TWO map, its the 8 AM discussion on it. I edited my post. Meant to say orange. 92L is getting hammered with west shear. Member Since: June 9, 2005 Posts: 23 Comments: 37044

391. AllStar17 6:09 PM GMT on August 24, 2009
Quoting TampaSpin: exactly Please do not quote caneluver, he is a troll. Member Since: June 29, 2009 Posts: 13 Comments: 5135

392. AllStar17 6:10 PM GMT on August 24, 2009
Quoting scottsvb: Well its defidently not a closed circulation yet @ the low levels.... weak low level vortex around 15.6N and 60.2W on close-up vis.... also midlevel circulation around 18.5N and 57.3W... Im still very skeptical of this thing making it all the way to a tropical system,... might be fighting some cold-core symptoms... maybe subtropical.... who knows of yet. Anyways a weaker non developed low will move more W or WNW with the LLF if its going to keep getting shared (as expected for the next 24-48hrs).... and btw we should of designated the area in the SW carribean as a TD and would probably be a TS in the next 12 -24hr before making landfall in Nicaragua... pressures are around 1006mb down there and a well defined LLC. Scottsvb I doubt it will be subtropical. If it develops, it should be warm core. Member Since: June 29, 2009 Posts: 13 Comments: 5135

393. IKE 6:10 PM GMT on August 24, 2009
Quoting btwntx08: u mean they're low on orange crayons I edited post. Member Since: June 9, 2005 Posts: 23 Comments: 37044

395. atmoaggie 6:11 PM GMT on August 24, 2009
Sorry, kid. Just a picking on you a little. I think everyone here knows what is posted at nhc.noaa.gov. I am one of those folks that doesn't care for 8 TWO posts in the blog at every update. If anyone that is in here really doesn't know where they are, nor goes to read them, well, [snip, be nice]. L8R, y'all. Member Since: August 16, 2007 Posts: 6 Comments: 12461

396. laflastormtracker 6:11 PM GMT on August 24, 2009
Quoting TampaSpin: exactly True that it is close to land but they should consider more interests close to land than in the open seas...more humans, more ship traffic as well...oh well roll tide roll :P

398. PortABeachBum 6:12 PM GMT on August 24, 2009
Quoting btwntx08: u doubled posted please get rid of one please thanks How about going to your own page and doing a little housework. Double post ! LOL! Member Since: October 4, 2007 Posts: 0 Comments: 198

399. hahaguy 6:13 PM GMT on August 24, 2009
Quoting NRAamy: Yellow alert for JFV's john.... LMAO Member Since: August 12, 2007 Posts: 2 Comments: 2838

400. IKE 6:13 PM GMT on August 24, 2009
They found the right crayon... Member Since: June 9, 2005 Posts: 23 Comments: 37044

401. cyclonekid 6:14 PM GMT on August 24, 2009
There they go. Member Since: July 14, 2009 Posts: 51 Comments: 1629

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