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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252. HIEXPRESS 4:51 PM GMT on August 24, 2009
Dana Summers Member Since: October 13, 2005 Posts: 4 Comments: 2153

254. Floodman 4:52 PM GMT on August 24, 2009
Quoting Grothar: Not likely! She learned that word from this blog and now says it in 3 languages. Now back to the weather. What is the little dot to which everyone is referring. Any current data which would inidicate as to when they expect formation, if any? The dot is actually a red area in the latest funktop for 92L; it's really just and area of higher clouds..as for development, it'll be slow; the shear in the area is a little high and won't back down for a few days not to mention the fact that this feature is pretty disorganized Member Since: August 2, 2006 Posts: 10 Comments: 9919

255. stormpetrol 4:52 PM GMT on August 24, 2009
I think the SW Caribbean might be worth for next days, jmo. Member Since: April 29, 2007 Posts: 0 Comments: 6394

257. wunderkidcayman 4:54 PM GMT on August 24, 2009
Quoting stormpetrol: I think the SW Caribbean might be worth for next days, jmo. please tell me more what going on in SW west Caribbean or what will happen Member Since: June 13, 2009 Posts: 2 Comments: 5381

258. Cavin Rawlins 4:54 PM GMT on August 24, 2009
Quoting NRAamy: "Please pass the Charmin...I think Bill is headed back this way..." lol lol, ouch! Member Since: July 24, 2005 Posts: 407 Comments: 19076

259. Grothar 4:56 PM GMT on August 24, 2009
It appears that a lot of energy is feeding into 92L from the SW. Does this help or hinder a developing system? Just an observation, but could that inflow be coming from the ULL to the NE of 92L? I just looked at the shear map and the upper winds are still quite high in the entire region. Member Since: July 17, 2009 Posts: 56 Comments: 19491

261. JLPR 4:58 PM GMT on August 24, 2009
I see 92L was able to revive the blog a little xD Member Since: September 4, 2007 Posts: 36 Comments: 5223

262. Cavin Rawlins 4:58 PM GMT on August 24, 2009
Wonder if August could spit out Danny and Erika? Member Since: July 24, 2005 Posts: 407 Comments: 19076

263. TheCaneWhisperer 4:58 PM GMT on August 24, 2009
Quoting pearlandaggie: I was aware of the situation with Isabel, but wasn't she a LOT more powerful than Vamco was during that shot? I guess the mesovortices can create all types of eye shapes... Isabel was yes but, I am pretty sure Vamco was a Cat 2 at that time. Apparent it's been weakening at a steady pace now.

265. kmanislander 4:59 PM GMT on August 24, 2009
Good morning Maybe the NAM does know its stuff after all. If this feature does not run ashore the NAM takes it across the NE corner of Nicaragua into the Gulf of Honduras. May go "yellow" if it stays over water in the SW Caribbean IMO Member Since: August 19, 2006 Posts: 0 Comments: 14939

266. Floodman 4:59 PM GMT on August 24, 2009
Quoting Grothar: Not likely! She learned that word from this blog and now says it in 3 languages. Now back to the weather. What is the little dot to which everyone is referring. Any current data which would inidicate as to when they expect formation, if any? Three langauges, huh? duende (Spanish) schleppangel (German) sleeplijn (Dutch) Member Since: August 2, 2006 Posts: 10 Comments: 9919

267. JLPR 5:00 PM GMT on August 24, 2009
I have no idea of where a center might be trying to form =S too many clouds moving at the same time lol Member Since: September 4, 2007 Posts: 36 Comments: 5223

268. GainesvilleGator 5:02 PM GMT on August 24, 2009
I see the armchair forecasters are out in full force. The only question I have is this: will 92L become "Danny" & threaten North Central Florida enough for the University of Florida to be shut down for a day? I need a hurricane day off! A White House press release said the projected budget deficits over the next 10 years will total $9 trillion. Did I stirr up the hornets nest enough? Member Since: September 11, 2005 Posts: 4 Comments: 732

270. nrtiwlnvragn 5:02 PM GMT on August 24, 2009
Quoting kmanislander: Good morning Maybe the NAM does know its stuff after all. If this feature does not run ashore the NAM takes it across the NE corner of Nicaragua into the Gulf of Honduras. May go "yellow" if it stays over water in the SW Caribbean IMO I am expecting that to be tagged 93L, nogaps and gfs also develop it. Member Since: September 23, 2005 Posts: 11 Comments: 8916

271. cyclonekid 5:03 PM GMT on August 24, 2009
92L and maybe possible 93L lookin good. :) Member Since: July 14, 2009 Posts: 51 Comments: 1619

272. cyclonekid 5:06 PM GMT on August 24, 2009
Quoting JLPR: I have no idea of where a center might be trying to form =S too many clouds moving at the same time lol Can you give me the link to that? Please? Member Since: July 14, 2009 Posts: 51 Comments: 1619

273. wunderkidcayman 5:06 PM GMT on August 24, 2009
Quoting kmanislander: Good morning Maybe the NAM does know its stuff after all. If this feature does not run ashore the NAM takes it across the NE corner of Nicaragua into the Gulf of Honduras. May go "yellow" if it stays over water in the SW Caribbean IMO thanks from when paloma sneaked up on us I became a little more alert if there any sort of good looking convection that can bring up a storm Member Since: June 13, 2009 Posts: 2 Comments: 5381

274. kmanislander 5:08 PM GMT on August 24, 2009
Quoting nrtiwlnvragn: I am expecting that to be tagged 93L, nogaps and gfs also develop it. I have been following the NAM forecast from Friday and it has consistently with every run developed a low in the SW Caribbean from the wave that was East of Trinidad late last week. The only difference from this and what it forecasted is that it had the low first show up just off the coast of Venezuela and migrate to the SW. It would seem that the energy was too far S over land to come together until now. Not a bad forecast some 4 days out. Member Since: August 19, 2006 Posts: 0 Comments: 14939

275. Cavin Rawlins 5:10 PM GMT on August 24, 2009
12Z Models Member Since: July 24, 2005 Posts: 407 Comments: 19076

277. nrtiwlnvragn 5:11 PM GMT on August 24, 2009
ASCAT pass on area NE of Panama Member Since: September 23, 2005 Posts: 11 Comments: 8916

278. cyclonekid 5:12 PM GMT on August 24, 2009
Danny and Erika, spinnin in the sea...S P I N N I N. LOL Member Since: July 14, 2009 Posts: 51 Comments: 1619

279. JLPR 5:12 PM GMT on August 24, 2009
Quoting cyclonekid: Can you give me the link to that? Please? sure here you go http://www.nwhhc.com/satellite.html Member Since: September 4, 2007 Posts: 36 Comments: 5223

280. Cavin Rawlins 5:14 PM GMT on August 24, 2009
Bills becomes extratropical after blowing into the Canadian Maritimes; Tropical Update BBL Member Since: July 24, 2005 Posts: 407 Comments: 19076

281. cyclonekid 5:14 PM GMT on August 24, 2009
Quoting JLPR: sure here you go http://www.nwhhc.com/satellite.html Thanks. :D Member Since: July 14, 2009 Posts: 51 Comments: 1619

282. Relix 5:16 PM GMT on August 24, 2009
StormW, could you tell me what effects could 92L have on Puerto Rico? Thanks in advance =) Member Since: August 3, 2006 Posts: 0 Comments: 2358

283. kmanislander 5:16 PM GMT on August 24, 2009
Steering is light North of Panama and there is a weakness heading up and through the Yucatan channel that would likely pull anything developing in SW Caribbean in that direction. Member Since: August 19, 2006 Posts: 0 Comments: 14939

284. cyclonekid 5:17 PM GMT on August 24, 2009
Guys, 2PM TWO will be coming out soon. What are your thoughts of what the TWO might hold? Member Since: July 14, 2009 Posts: 51 Comments: 1619

285. WxLogic 5:18 PM GMT on August 24, 2009
15Z VORT charts out... 850MB to 700MB VORT MAX suggest the that the best low level convergence regions appears to be ~18N59W, there's also a developing 500MB VORT MAX a bit further back (due to high shear, not surprisingly from the TUTT to the NW of 92L) at ~18N56W where the heaviest convection appears to be concentrated on. Low level convergence appears to be increasing a bit near 18N59W or close to the 850MB VORT MAX. Finally, current steering flow for this type of system will continue to promote a WNW movement under the strong Bermuda high to its N. Member Since: August 14, 2008 Posts: 4 Comments: 4666

286. kmanislander 5:18 PM GMT on August 24, 2009
Back later Member Since: August 19, 2006 Posts: 0 Comments: 14939

287. miken62 5:19 PM GMT on August 24, 2009
A third victim of Hurricane Bill was a young man in his 30's I believe swept off the rocks in Nahant,Ma ....just off the coast of Lynn Mass..............his first name was Steven.....he was fishing ...and was washed off the rocks on Saturday and died at a Boston hospital late Sunday night...... WHY DO PEOPLE NOT HEED WARNINGS ...they are there for a reason...... Member Since: January 14, 2003 Posts: 0 Comments: 213

288. nrtiwlnvragn 5:19 PM GMT on August 24, 2009
ATTENTION...NATIONAL HURRICANE CENTER NCEP COUPLED GFDL HURRICANE MODEL FORECAST MADE FOR TROPICAL DEPRESSION INVEST 92L INITIAL TIME 12Z AUG 24 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 16.1 56.3 290./20.0 STORM DISSIPATED AT 0 HRS AT THE ABOVE PSN. Not suprised, GFDL needs a stronger initial system to hang onto it. Member Since: September 23, 2005 Posts: 11 Comments: 8916

289. HurricaneKyle 5:21 PM GMT on August 24, 2009
There is some 850 vort in the Caribbean it would appear. Member Since: August 10, 2009 Posts: 3 Comments: 672

290. OSUWXGUY 5:21 PM GMT on August 24, 2009
Quoting nrtiwlnvragn: I am expecting that to be tagged 93L, nogaps and gfs also develop it. Yeah. I think it may also be tagged. I'm not sure with the fast steering flow that it will have time to develop before running into Costa Rica. Looks dead east to west to me so I doubt it reaches the Gulf of Honduras. Maybe it will get going in the EPAC...

291. kmanislander 5:21 PM GMT on August 24, 2009
Quoting HurricaneKyle: There is some 850 vort in the Caribbean it would appear. Indeed there is, and stronger than the vorticity with 92L 850 mb vort map Member Since: August 19, 2006 Posts: 0 Comments: 14939

292. cyclonekid 5:21 PM GMT on August 24, 2009
Very good eye on Vamco. Am Impressed. Member Since: July 14, 2009 Posts: 51 Comments: 1619

293. hurricanemaniac123 5:23 PM GMT on August 24, 2009
Quoting cyclonekid: Guys, 2PM TWO will be coming out soon. What are your thoughts of what the TWO might hold? Probably one or two yellow circles (the other being the disturbance in near Panama) in the atlantic, but there is a chance that 92L could be an orange circle. Member Since: September 21, 2008 Posts: 9 Comments: 688

294. kmanislander 5:23 PM GMT on August 24, 2009
Quoting OSUWXGUY: Yeah. I think it may also be tagged. I'm not sure with the fast steering flow that it will have time to develop before running into Costa Rica. Looks dead east to west to me so I doubt it reaches the Gulf of Honduras. Maybe it will get going in the EPAC... The steering does not look fast to me but it is close to land and may well go ashore unless it lifts to the NW as called for by the NAM Member Since: August 19, 2006 Posts: 0 Comments: 14939

295. AllStar17 5:24 PM GMT on August 24, 2009
kman, Good observation! This disturbance could develop more rapidly than the 92L. 850 mb. vort. is good, and you are correct about the movement. Maybe northwest if it stays offshore, maybe grazing Honduras/Nicaragua. Member Since: June 29, 2009 Posts: 13 Comments: 5135

296. Floodman 5:26 PM GMT on August 24, 2009
Quoting kmanislander: Indeed there is, and stronger than the with 92L 850 mb vort map It extends upward to 500mb as well... Member Since: August 2, 2006 Posts: 10 Comments: 9919

298. nrtiwlnvragn 5:27 PM GMT on August 24, 2009
Quoting OSUWXGUY: Yeah. I think it may also be tagged. I'm not sure with the fast steering flow that it will have time to develop before running into Costa Rica. Looks dead east to west to me so I doubt it reaches the Gulf of Honduras. Maybe it will get going in the EPAC... I see what you are saying, thats the GFS solution into the East Pacific. NOGAPS still (12Z) wants to take it up to the Yucatan. Member Since: September 23, 2005 Posts: 11 Comments: 8916

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