Dr. Jeff Masters' WunderBlog

Bill is gone; Invest 92 pops up

Posted by: Dr. Jeff Masters, 02:08 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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1202. Stormchaser2007 01:56 AM GMT on August 25, 2009
OHC in the Caribbean is off the scale. Fifty-fifty shot that a TC ever gets to use that energy this year. Member Since: Juni 9, 2007 Posts: 4 Comments: 15294

1203. JLPR 01:56 AM GMT on August 25, 2009
wave about to exit Africa is looking good Member Since: September 4, 2007 Posts: 36 Comments: 5223

1204. canesrule1 01:56 AM GMT on August 25, 2009
Quoting extreme236: Uh thats the current shear map. whatever look at post 1196

1206. Drakoen 01:57 AM GMT on August 25, 2009
The GFS forecast already looks unrealistic taking the system to 24N in 24 hours. Member Since: Oktober 28, 2006 Posts: 57 Comments: 29012

1207. KEEPEROFTHEGATE (Mod) 01:57 AM GMT on August 25, 2009
Quoting litestar: Keeper of the gate are you there? YES Member Since: Juli 15, 2006 Posts: 147 Comments: 41318

1208. canesrule1 01:57 AM GMT on August 25, 2009
Quoting Booeyb52: Nah StormW, your girlfriend sent me that one last night. She's kind of cute with them ears. go away, troll, no one wants u except ur mom.

1209. mobilegirl81 01:58 AM GMT on August 25, 2009
So forecasts indicate an upward MJO and a negative NAO in early to mid September? Member Since: August 31, 2008 Posts: 0 Comments: 833

1210. Stormchaser2007 01:58 AM GMT on August 25, 2009
Nvm Member Since: Juni 9, 2007 Posts: 4 Comments: 15294

1211. AllStar17 01:58 AM GMT on August 25, 2009
Quoting Booeyb52: Nah StormW, your girlfriend sent me that one last night. She's kind of cute with them ears. Reported. Member Since: Juni 29, 2009 Posts: 13 Comments: 5145

1213. KEEPEROFTHEGATE (Mod) 01:59 AM GMT on August 25, 2009
we got to wait til that gets over the water for 24 first JLPR Member Since: Juli 15, 2006 Posts: 147 Comments: 41318

1214. kmanislander 01:59 AM GMT on August 25, 2009
Quoting Stormchaser2007: OHC in the Caribbean is off the scale. Fifty-fifty shot that a TC ever gets to use that energy this year. There will likely be at least one and if so CAT 5 on the cards Member Since: August 19, 2006 Posts: 0 Comments: 14988

1215. litestar 01:59 AM GMT on August 25, 2009
need to know? at midnight will north brevard Co Fla be clear of clouds,rain,lighting... PLEASE answer>>>> melbourne radar clutter..cant see any thing...help Star

1217. canesrule1 01:59 AM GMT on August 25, 2009
The model im using for forecasting is the CLIP.

1218. bwat 02:00 AM GMT on August 25, 2009
total newb question, but if it is august 24th 10:00 pm eastern time, what does that translate to in "Z" time? I get so confused when you folks talk about the 18z, ect. models. Thanks in advance. Member Since: August 18, 2009 Posts: 0 Comments: 338

1219. AllStar17 02:00 AM GMT on August 25, 2009
. Member Since: Juni 29, 2009 Posts: 13 Comments: 5145

1220. Stormchaser2007 02:00 AM GMT on August 25, 2009
Quoting mobilegirl81: So forecasts indicate an upward MJO and a negative NAO in early to mid September? No... MJO go positive in September according to the GFS. This WILL change many times though. Member Since: Juni 9, 2007 Posts: 4 Comments: 15294

1221. KoritheMan 02:00 AM GMT on August 25, 2009
Quoting Booeyb52: Nah StormW, your girlfriend sent me that one last night. She's kind of cute with them ears. Who the hell is this nobody? Member Since: Marts 7, 2007 Posts: 421 Comments: 15640

1222. Joanie38 02:00 AM GMT on August 25, 2009
STORMW I am your fan....your forecasts are execellent!!!! :) Member Since: Juni 16, 2008 Posts: 0 Comments: 467

1223. AllStar17 02:00 AM GMT on August 25, 2009
Drak, what does the DAM model say? Member Since: Juni 29, 2009 Posts: 13 Comments: 5145

1224. JLPR 02:00 AM GMT on August 25, 2009
Quoting KEEPEROFTHEGATE: we got to wait til that gets over the water for 24 first JLRP Obviously =P but what I said is it looks good now if it manages to maintain itself once it hits water is another story xD Member Since: September 4, 2007 Posts: 36 Comments: 5223

1225. KEEPEROFTHEGATE (Mod) 02:01 AM GMT on August 25, 2009
Quoting kmanislander: There will likely be at least one and if so CAT 5 on the cards a big cat 5 kman Member Since: Juli 15, 2006 Posts: 147 Comments: 41318

1228. kmanislander 02:02 AM GMT on August 25, 2009
Quoting bwat: total newb question, but if it is august 24th 10:00 pm eastern time, what does that translate to in "Z" time? I get so confused when you folks talk about the 18z, ect. models. Thanks in advance. 2200 Member Since: August 19, 2006 Posts: 0 Comments: 14988

1229. hunkerdown 02:02 AM GMT on August 25, 2009
Quoting litestar: need to know? at midnight will north brevard Co Fla be clear of clouds,rain,lighting... PLEASE answer>>>> melbourne radar clutter..cant see any thing...help Star for the shuttle launch ? Member Since: August 15, 2008 Posts: 0 Comments: 2514

1230. JLPR 02:02 AM GMT on August 25, 2009
Quoting Stormchaser2007: No... MJO go positive in September according to the GFS. This WILL change many times though. I dont like the Green colors there xD Member Since: September 4, 2007 Posts: 36 Comments: 5223

1231. hurricane23 02:02 AM GMT on August 25, 2009
Something tells me the UKMET maybe on to something. Member Since: Maj 14, 2006 Posts: 8 Comments: 13327

1232. canesrule1 02:02 AM GMT on August 25, 2009
Satellite presentation has improved considerably in the previous 9 hours with 92L:

1233. hunkerdown 02:03 AM GMT on August 25, 2009
Quoting canesrule1: The model im using for forecasting is the CLIP. I hope you are kidding... Member Since: August 15, 2008 Posts: 0 Comments: 2514

1234. KEEPEROFTHEGATE (Mod) 02:03 AM GMT on August 25, 2009
Quoting KoritheMan: Who the hell is this nobody? nothing but empty space korit Member Since: Juli 15, 2006 Posts: 147 Comments: 41318

1236. mobilegirl81 02:03 AM GMT on August 25, 2009
Quoting Stormchaser2007: No... MJO go positive in September according to the GFS. This WILL change many times though. What about negative NAO and lower trade winds over tropical atlantic during that yime frame? Member Since: August 31, 2008 Posts: 0 Comments: 833

1237. hunkerdown 02:04 AM GMT on August 25, 2009
Quoting AllStar17: Drak, too early to say where it will ultimately end up, right? the hair just stood up on my arms, that sounds eerily like a WS question... Member Since: August 15, 2008 Posts: 0 Comments: 2514

1238. AllStar17 02:04 AM GMT on August 25, 2009
Member Since: Juni 29, 2009 Posts: 13 Comments: 5145

1239. canesrule1 02:04 AM GMT on August 25, 2009
Quoting hurricane23: Something tells me the UKMET maybe on to something. link please, thanks

1240. AllStar17 02:05 AM GMT on August 25, 2009
Quoting hunkerdown: the hair just stood up on my arms, that sounds eerily like a WS question... Well I will remove that, then, because I AM NOT WS! What an evil statement! j/k Member Since: Juni 29, 2009 Posts: 13 Comments: 5145

1241. Drakoen 02:05 AM GMT on August 25, 2009
Quoting AllStar17: Drak, too early to say where it will ultimately end up, right? The GFS is too far north. At this time, I agree with the ECMWF and UKMET solution. Member Since: Oktober 28, 2006 Posts: 57 Comments: 29012

1242. hydrus 02:05 AM GMT on August 25, 2009
Quoting hurricane23: Something tells me the UKMET maybe on to something. What is the UKMET saying 23? Member Since: September 27, 2007 Posts: 1 Comments: 14682

1243. bwat 02:06 AM GMT on August 25, 2009
Once again thanks for all the help yall, I'm off to bed. BTW don't worry about the troll StormW, gotta feel bad for someone who can't spell buoy correctly. L8R Member Since: August 18, 2009 Posts: 0 Comments: 338

1244. Stormchaser2007 02:06 AM GMT on August 25, 2009
Quoting mobilegirl81: What about negative NAO and lower trade winds over tropical atlantic during that yime frame? That seems correct. Member Since: Juni 9, 2007 Posts: 4 Comments: 15294

1245. canesrule1 02:06 AM GMT on August 25, 2009
Quoting hunkerdown: I hope you are kidding... why do u say that, huh?

1246. CaneAddict 02:06 AM GMT on August 25, 2009
Quoting extreme236: Yup I agree. I agree. Member Since: Oktober 5, 2007 Posts: 3 Comments: 2151

1247. JLPR 02:06 AM GMT on August 25, 2009
Link to the UKmet please =] Member Since: September 4, 2007 Posts: 36 Comments: 5223

1248. AllStar17 02:06 AM GMT on August 25, 2009
Quoting Drakoen: The GFS is too far north. At this time, I agree with the ECMWF and UKMET solution. OK. Member Since: Juni 29, 2009 Posts: 13 Comments: 5145

1249. Joanie38 02:07 AM GMT on August 25, 2009
Quoting StormW: And you are appreciated! Awwwww, thanks STORMW :) SO ARE YOU!!!! Member Since: Juni 16, 2008 Posts: 0 Comments: 467

1250. geepy86 02:07 AM GMT on August 25, 2009
bin in and out. did jfv/ws get banned again? Member Since: August 19, 2008 Posts: 0 Comments: 1613

1251. canesrule1 02:07 AM GMT on August 25, 2009
Quoting Drakoen: The GFS is too far north. At this time, I agree with the ECMWF and UKMET solution. UKMET and ECMWF links please, thank you.

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