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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1051. InTheCone 12:56 AM GMT on August 25, 2009
Quoting centex: Where is that wave which Doc mentioned for later in the week? Next.... Member Since: September 1, 2007 Posts: 0 Comments: 1979

1053. BahaHurican 12:56 AM GMT on August 25, 2009
92L starting to build some white tops as we head towards the late night hours.... Member Since: October 25, 2005 Posts: 19 Comments: 17645

1054. WxLogic 12:57 AM GMT on August 25, 2009
Good evening... Member Since: August 14, 2008 Posts: 4 Comments: 4667

1055. BahaHurican 12:58 AM GMT on August 25, 2009
Quoting JLPR: believe it or not 93L is better organized that 92L =P Easy to believe, looking at them comparatively, especially looped.... Member Since: October 25, 2005 Posts: 19 Comments: 17645

1056. Stormchaser2007 12:58 AM GMT on August 25, 2009
I see we have 93L It should be over land before it can have a chance to develop. Member Since: June 9, 2007 Posts: 4 Comments: 15248

1058. InTheCone 1:01 AM GMT on August 25, 2009
Quoting StormW: Thanks! Always good to see you as well. I do know they read my stuff though. Them and alot more!! Always good solid info. Member Since: September 1, 2007 Posts: 0 Comments: 1979

1059. CaneAddict 12:59 AM GMT on August 25, 2009
Quoting extreme236: Uh no. 92L is going to be in a more favorable environment. Your using a current shear map. 93L look's to be the RIP if you ask me. Besides if it does develop it probably wouldn't occur until it crosses Mexico. It better hurry up and develop if it's going to do so. Member Since: October 5, 2007 Posts: 3 Comments: 2151

1060. KimberlyB 1:00 AM GMT on August 25, 2009
Quoting StormW: Thanks! Always good to see you as well. I do know they read my stuff though. Really? Huh. I'll just add that to my list of reasons your one of the few I actually trust and listen too. lol Member Since: October 21, 2007 Posts: 27 Comments: 328

1062. Orcasystems 1:01 AM GMT on August 25, 2009
AOI AOI Member Since: October 1, 2007 Posts: 77 Comments: 26077

1063. JLPR 1:01 AM GMT on August 25, 2009
92L's 850mb vorticity is further south close to 18N 61W and its 500mb vorticity is at: 20N 60W so yep very disorganized xD Member Since: September 4, 2007 Posts: 36 Comments: 5223

1064. BoynSea 1:01 AM GMT on August 25, 2009
1053. BahaHurican 12:56 AM GMT on August 25, 2009 This one (92L) seems to have you a bit concerned, Baha. I think it's going to track a bit more North than predicted....but then the shear drops off. Comments? Boynsea Member Since: October 8, 2007 Posts: 0 Comments: 87

1065. centex 1:02 AM GMT on August 25, 2009
Quoting InTheCone: Next.... Thanks, 94L maybe in a couple of days. Member Since: August 10, 2007 Posts: 0 Comments: 2856

1066. CaneAddict 1:02 AM GMT on August 25, 2009
By the way I finally got my new computer in the mail so that's why I am back. The whole time Bill was around I had no computer..go figure. Member Since: October 5, 2007 Posts: 3 Comments: 2151

1067. JLPR 1:02 AM GMT on August 25, 2009
Quoting CaneAddict: 93L look's to be the RIP if you ask me. Besides if it does develop it probably wouldn't occur until it crosses Mexico. It better hurry up and develop if it's going to do so. lol that would be Central America not Mexico =P Member Since: September 4, 2007 Posts: 36 Comments: 5223

1068. FlyinFish 1:03 AM GMT on August 25, 2009
Member Since: June 8, 2008 Posts: 0 Comments: 43

1069. cyclonekid 1:03 AM GMT on August 25, 2009
Member Since: July 14, 2009 Posts: 51 Comments: 1629

1070. CaneAddict 1:03 AM GMT on August 25, 2009
It's quite possible that sometime in the next week or so we will be tracking another cape-verde system. Member Since: October 5, 2007 Posts: 3 Comments: 2151

1071. extreme236 1:04 AM GMT on August 25, 2009
If 93L can flare some convection real fast it would have a chance to develop before moving inland (Claudette type of rapid development) but only a TD or weak TS at best. Member Since: August 2, 2007 Posts: 19 Comments: 19234

1072. Relix 1:06 AM GMT on August 25, 2009
Quoting JLPR: 92L's 850mb vorticity is further south close to 18N 61W and its 500mb vorticity is at: 20N 60W so yep very disorganized xD Should provide great entertainment here in PR =P Member Since: August 3, 2006 Posts: 0 Comments: 2358

1073. hurricane23 1:04 AM GMT on August 25, 2009
00z Bam models continue to suggest quick recurve with 92L. Member Since: May 14, 2006 Posts: 8 Comments: 13276

1074. TexasHurricane 1:04 AM GMT on August 25, 2009
Quoting InTheCone: My only comment about 93l is that if it had been going NW instead of W, we would have a lot of very interested people in here... Hi Everyone, Isn't it kinda odd that this is moving west? I was thinking these usually went northwest or in that general direction...hmmmmm,maybe not. Member Since: July 2, 2009 Posts: 0 Comments: 2811

1076. CaneAddict 1:05 AM GMT on August 25, 2009
Quoting JLPR: lol that would be Central America not Mexico =P True...lol so used to saying Mexico. Member Since: October 5, 2007 Posts: 3 Comments: 2151

1077. canesrule1 1:05 AM GMT on August 25, 2009
93L vs. 92L 93L: 92L:

1078. JLPR 1:05 AM GMT on August 25, 2009
Quoting JLPR: 92L's 850mb vorticity is further south close to 18N 61W and its 500mb vorticity is at: 20N 60W so yep very disorganized xD looking at the satellite you can see the MLC producing the strongest convection and to its SW would be the future LLC Member Since: September 4, 2007 Posts: 36 Comments: 5223

1079. hurricane23 1:06 AM GMT on August 25, 2009
Quoting CaneAddict: It's quite possible that sometime in the next week or so we will be tracking another cape-verde system. What not conditions look pretty favorable BUT just one issue our parade of trofs just wont give way. Member Since: May 14, 2006 Posts: 8 Comments: 13276

1080. extreme236 1:06 AM GMT on August 25, 2009
Quoting StSimonsIslandGAGuy: 93L has a better chance of hitting Hawaii than any other state. And the African wave just coming off now is a bit far to the north, unless the low forms on the southern end of the wave, I think it will be too far north to make it all the way across the Atlantic. I think the one that has the highest chance for development is the one over Central Africa, that is farther south. Member Since: August 2, 2007 Posts: 19 Comments: 19234

1081. CaneAddict 1:07 AM GMT on August 25, 2009
Quoting StormW: Yea...the first night Barometer Bob had me on as a guest, he was explaining he see's some good names receiving my forecasts. He had also been in contact with the guys at NHC, and stated Jack Beven, and a couple other forecasters told him I do excellent work. You do some great forecasting..I know first hand as I have met you in person and you made everything so easy to understand. Keep up the good work StormW! Member Since: October 5, 2007 Posts: 3 Comments: 2151

1082. canesrule1 1:07 AM GMT on August 25, 2009
my chances with current models indication: 8% Florida 32% Carolinas 60% recurvature (possibly a fish or Bermuda hit).

1083. Joanie38 1:07 AM GMT on August 25, 2009
Hello everyone!!!! Hello StormW..:) It seems the GOM has been lucky SO FAR....I am in SWLA. Member Since: June 16, 2008 Posts: 0 Comments: 461

1084. JLPR 1:08 AM GMT on August 25, 2009
Quoting Relix: Should provide great entertainment here in PR =P it should make our lives miserable tomorrow with lots of rain =\ Member Since: September 4, 2007 Posts: 36 Comments: 5223

1085. extreme236 1:08 AM GMT on August 25, 2009
92L looks a bit more concentrated than earlier and firing off some new convection. 93L still looks interesting despite its short lived nature. Member Since: August 2, 2007 Posts: 19 Comments: 19234

1086. Relix 1:08 AM GMT on August 25, 2009
Member Since: August 3, 2006 Posts: 0 Comments: 2358

1087. CaneAddict 1:08 AM GMT on August 25, 2009
Quoting extreme236: I think the one that has the highest chance for development is the one over Central Africa, that is farther south. I saw that also...i'm placing my bets on that one for development. Member Since: October 5, 2007 Posts: 3 Comments: 2151

1088. cyclonekid 1:09 AM GMT on August 25, 2009
That was easy Member Since: July 14, 2009 Posts: 51 Comments: 1629

1089. Relix 1:09 AM GMT on August 25, 2009
850MB Steering Member Since: August 3, 2006 Posts: 0 Comments: 2358

1090. Yalahaman 1:09 AM GMT on August 25, 2009
Amen to that Quoting crzyboutncweather: Hopefully we on the east coast will have no worries with 92. Everytime I come to this site and read the blogs the storms stay well away from NC. I am hoping my streak stays intact and nobody has to deal with anything. When I was younger and didn't own a house I thought they were cool. Hurrican Fran came up the mouth of the cape fear and we lost power for two weeks. Trees down everywhere and about 15k worth of damage to my folks house. I no longer think they are cool. Member Since: August 20, 2009 Posts: 1 Comments: 107

1091. CaneAddict 1:10 AM GMT on August 25, 2009
Quoting extreme236: 92L looks a bit more concentrated than earlier and firing off some new convection. 93L still looks interesting despite its short lived nature. Yeah, curious to how it utilizes diurnal max. Member Since: October 5, 2007 Posts: 3 Comments: 2151

1092. WxLogic 1:11 AM GMT on August 25, 2009
I would have been impressed by the TSTM development in the area of 92L... but is not being maintain/generated solely by self. 21Z VORT Charts do show VORT MAX present now from 850MB to 500MB... and due to the shear you can clearly see that these vortexes are not vertically stacked and with good reason. With the 500MB VORT MAX closer to the main TSTM clusters and the low level vortexes and primary low level circulation further to the SW or at the northern edge of the Leeward Islands. I do believe the TUTT to its NW will be making it company for a good 48hrs or so before it starts moving out. Member Since: August 14, 2008 Posts: 4 Comments: 4667

1093. Stormchaser2007 1:11 AM GMT on August 25, 2009
Quoting extreme236: I think the one that has the highest chance for development is the one over Central Africa, that is farther south. Looks pretty solid. Not really any SAL to worry about. Member Since: June 9, 2007 Posts: 4 Comments: 15248

1094. canesrule1 1:12 AM GMT on August 25, 2009
Quoting Relix: 850MB Steering seems to move straight towards Florida them scrape the coast and curve, imo.

1097. hurricane23 1:13 AM GMT on August 25, 2009
Bill might have thrown a line out to 92L. Member Since: May 14, 2006 Posts: 8 Comments: 13276

1098. Stormchaser2007 1:14 AM GMT on August 25, 2009
Quoting canesrule1: seems to move straight towards Florida them scrape the coast and curve, imo. The steering is going to change many times before 92L will become more organized. Member Since: June 9, 2007 Posts: 4 Comments: 15248

1100. Eagle300 1:14 AM GMT on August 25, 2009
What we have to realize is that the difference in wether 93L develops or stays an invest is nothing. The bottom line is regardless of a closed circulation of not, it is going to cause huge problems as far as flooding. Remember that.

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