Dr. Jeff Masters' WunderBlog

Bill is gone; Invest 92 pops up

Posted by: Dr. Jeff Masters, 2:08 PM GMT en Agosto 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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1151. Stormchaser2007 1:39 AM GMT en Agosto 25, 2009
Quoting hurricane23: Considering the unusually strong cold fronts moving off the EC in the past weeks (including the present cold front), it seems that should continue to keep the subtropical ridge east of it's normal position, so, that would continue to favor Bertha 08 type tracks... Nothing wrong with that. Member Since: Junio 9, 2007 Posts: 4 Comments: 15296

1152. extreme236 1:39 AM GMT en Agosto 25, 2009
Quoting Stormchaser2007: Looks similar to the pre-Noel disturbance. Actually not looking too bad. Member Since: Agosto 2, 2007 Posts: 19 Comments: 19234

1153. canesrule1 1:39 AM GMT en Agosto 25, 2009
Quoting Stormchaser2007: Looks similar to the pre-Noel disturbance. i agree but i don't think it will be doing a path like him:

1154. WxLogic 1:40 AM GMT en Agosto 25, 2009
Quoting kmanislander: Is 13N 32W a sleeper ?? Good evening folks Will not be surprised... Member Since: Agosto 14, 2008 Posts: 4 Comments: 4721

1155. hurricane23 1:41 AM GMT en Agosto 25, 2009
Quoting Stormchaser2007: Nothing wrong with that. Sure...1995 is a good example of what happens when the Bermuda High is displaced more east..lots of Cape Verde systems but all of them recurved well East of the CONUS. Note the Leeward Islands had some activity though. Member Since: Mayo 14, 2006 Posts: 8 Comments: 13331

1156. Stormchaser2007 1:41 AM GMT en Agosto 25, 2009
Quoting extreme236: Actually not looking too bad. My bet is that by Wednesday we should see TD-5 from this. Member Since: Junio 9, 2007 Posts: 4 Comments: 15296

1157. canesrule1 1:42 AM GMT en Agosto 25, 2009
Looks very sheared, then again, it has an upper level low ripping its head and it is under 30-40+ knots of shear.

1158. KoritheMan 1:42 AM GMT en Agosto 25, 2009
South Carolina and points northward need to keep a close eye on 92L over the next several days. It may come to a near stall over the Gulf Stream in about 72 hours, where it will have a decent chance at organizing into a tropical cyclone. Member Since: Marzo 7, 2007 Posts: 421 Comments: 15643

1159. Stormchaser2007 1:44 AM GMT en Agosto 25, 2009
The GFS really did a 360 with the new MJO forecast. Member Since: Junio 9, 2007 Posts: 4 Comments: 15296

1160. centex 1:43 AM GMT en Agosto 25, 2009
Quoting hurricane23: Sure...1995 is a good example of what happens when the Bermuda High is displaced more east..lots of Cape Verde systems but all of them recurved well East of the CONUS. Note the Leeward Islands had some activity though. That looks fishy Member Since: Agosto 10, 2007 Posts: 0 Comments: 2876

1161. canesrule1 1:43 AM GMT en Agosto 25, 2009
Quoting Stormchaser2007: My bet is that by Wednesday we should see TD-5 from this. i totally utterly completely without a shadow of a doubt disagree with you.

1162. extreme236 1:43 AM GMT en Agosto 25, 2009
Quoting Stormchaser2007: My bet is that by Wednesday we should see TD-5 from this. Yup I agree. Member Since: Agosto 2, 2007 Posts: 19 Comments: 19234

1163. TexasHurricane 1:43 AM GMT en Agosto 25, 2009
Quoting Stormchaser2007: The GFS really did a 360 with the new MJO forecast. meaning? potential for more storms or less? Member Since: Julio 2, 2009 Posts: 0 Comments: 2811

1164. caneswatch 1:44 AM GMT en Agosto 25, 2009
Quoting Stormchaser2007: The GFS really did a 360 with the new MJO forecast. Link? Member Since: Octubre 8, 2008 Posts: 14 Comments: 4479

1165. extreme236 1:44 AM GMT en Agosto 25, 2009
Quoting canesrule1: i totally utterly completely without a shadow of a doubt disagree with you. Based on what? Gut assumption? lol Member Since: Agosto 2, 2007 Posts: 19 Comments: 19234

1166. kmanislander 1:44 AM GMT en Agosto 25, 2009
Quoting WxLogic: Will not be surprised... This year is starting to feel more and more like 2004. Sort of quiet out of the gate and then 8 weeks of hyper activity. The heat in the Caribbean has been unbelievable. High 90's most days with a heat index near 115 F. Very little rain. Hurricanes are nature's way of transferring high heat from the tropics to places far N. I can't believe that the season will limp to a finish the way it has started. Member Since: Agosto 19, 2006 Posts: 0 Comments: 14988

1168. KEEPEROFTHEGATE (Mod) 1:44 AM GMT en Agosto 25, 2009
xx/xx/92L MARK 18.9N/60.1W Member Since: Julio 15, 2006 Posts: 147 Comments: 41332

1169. KoritheMan 1:45 AM GMT en Agosto 25, 2009
One big positive for 92L that so many other systems have not had thus far, is an abundance of mid-level moisture. Water vapor imagery shows quite a moist environment in the vicinity of the disturbance, with any SAL located well to the east. Member Since: Marzo 7, 2007 Posts: 421 Comments: 15643

1170. Stormchaser2007 1:45 AM GMT en Agosto 25, 2009
Quoting KoritheMan: South Carolina and points northward need to keep a close eye on 92L over the next several days. It may come to a near stall over the Gulf Stream in about 72 hours, where it will have a decent chance at organizing into a tropical cyclone. Exactly...high SSTs and an anticyclone. Anyways some pretty interesting climatological tracks here. Member Since: Junio 9, 2007 Posts: 4 Comments: 15296

1171. canesrule1 1:45 AM GMT en Agosto 25, 2009
Quoting extreme236: Yup I agree. well it will take about 48-72 hours normally for it to develop a LLC but it can also take less then 24 rarely though, the upper level low needs to weaken, and shear is going to be around 40+ knots for the next 36 to 48 hours or so.

1173. Drakoen 1:46 AM GMT en Agosto 25, 2009
92L is acquiring a mid level circulation that could work down to the surface Member Since: Octubre 28, 2006 Posts: 57 Comments: 29012

1174. canesrule1 1:46 AM GMT en Agosto 25, 2009
Quoting extreme236: Based on what? Gut assumption? lol lol, look at post 1171.

1175. bwat 1:47 AM GMT en Agosto 25, 2009
Quoting StormW: ha ha, perfect. Could not of said it better myself. Member Since: Agosto 18, 2009 Posts: 0 Comments: 338

1176. extreme236 1:49 AM GMT en Agosto 25, 2009
Quoting canesrule1: well it will take about 48-72 hours normally for it to develop a LLC but it can also take less then 24 rarely though, the upper level low needs to weaken, and shear is going to be around 40+ knots for the next 36 to 48 hours or so. No its not going to be 40+kts for the next 36-48 hours. It RARELY takes 2-3 days for a circulation to form. Member Since: Agosto 2, 2007 Posts: 19 Comments: 19234

1177. Booeyb52 1:48 AM GMT en Agosto 25, 2009
I like the self-portrait StormW, cute.

1178. canesrule1 1:48 AM GMT en Agosto 25, 2009
Quoting canesrule1: well it will take about 48-72 hours normally for it to develop a LLC but it can also take less then 24 rarely though, the upper level low needs to weaken, and shear is going to be around 40+ knots for the next 36 to 48 hours or so. and it is not vertically stacked from the 850MB level all the way down to 200MB, ughhh.

1179. Stormchaser2007 1:48 AM GMT en Agosto 25, 2009
Quoting canesrule1: i totally utterly completely without a shadow of a doubt disagree with you. Based on what. The 00z models dont count lol Member Since: Junio 9, 2007 Posts: 4 Comments: 15296

1181. Stormchaser2007 1:49 AM GMT en Agosto 25, 2009
Quoting TexasHurricane: meaning? potential for more storms or less? Doesnt mean anything yet... The GFS changes too many times. Member Since: Junio 9, 2007 Posts: 4 Comments: 15296

1182. JLPR 1:49 AM GMT en Agosto 25, 2009
Wow the MLC is firing all its guns tonight so now the MLC is the dominant one Member Since: Septiembre 4, 2007 Posts: 36 Comments: 5223

1183. KoritheMan 1:49 AM GMT en Agosto 25, 2009
Quoting Stormchaser2007: Exactly...high SSTs and an anticyclone. Anyways some pretty interesting climatological tracks here. Can't view that page. :/ Member Since: Marzo 7, 2007 Posts: 421 Comments: 15643

1184. AllStar17 1:49 AM GMT en Agosto 25, 2009
Quoting canesrule1: well it will take about 48-72 hours normally for it to develop a LLC but it can also take less then 24 rarely though, the upper level low needs to weaken, and shear is going to be around 40+ knots for the next 36 to 48 hours or so. Nope, you're wrong. Shear is already lessening over 92L as the ULL weakens. Member Since: Junio 29, 2009 Posts: 13 Comments: 5145

1185. canesrule1 1:50 AM GMT en Agosto 25, 2009
Quoting extreme236: No its not going to be 40+kts for the next 36-48 hours. It RARELY takes 2-3 days for a circulation to form. hmmmmm:

1186. extreme236 1:50 AM GMT en Agosto 25, 2009
Quoting canesrule1: and it is not vertically stacked from the 850MB level all the way down to 200MB, ughhh. Were not talking about now, were talking about Wednesday. Member Since: Agosto 2, 2007 Posts: 19 Comments: 19234

1187. Stormchaser2007 1:50 AM GMT en Agosto 25, 2009
Quoting KoritheMan: Can't view that page. :/ Try the base page here and go to the analog tracks for 92L. Member Since: Junio 9, 2007 Posts: 4 Comments: 15296

1188. Stoopid1 1:50 AM GMT en Agosto 25, 2009
Quoting Drakoen: 92L is acquiring a mid level circulation that could work down to the surface Good evening Drak. 92L holding well despite the shear. Looks like it has a good chance to be the next TD in a couple days, especially since shear is forecast to decrease. 92L also has a moist environment, and I do see the MLC you spoke of. Definitely organizing right now. Member Since: Agosto 6, 2007 Posts: 21 Comments: 2390

1189. centex 1:51 AM GMT en Agosto 25, 2009
Quoting kmanislander: This year is starting to feel more and more like 2004. Sort of quiet out of the gate and then 8 weeks of hyper activity. The heat in the Caribbean has been unbelievable. High 90's most days with a heat index near 115 F. Very little rain. Hurricanes are nature's way of transferring high heat from the tropics to places far N. I can't believe that the season will limp to a finish the way it has started. Yea was there a few weeks ago, chartered a boat from Captain Marvin, he still hangs out on pouch. It was hot even sitting in the shade eating marinated conk and a cold Jamacian beer. Member Since: Agosto 10, 2007 Posts: 0 Comments: 2876

1190. AllStar17 1:51 AM GMT en Agosto 25, 2009
Also, I am not completely sold on this system recurving yet. It is still too early to tell. Member Since: Junio 29, 2009 Posts: 13 Comments: 5145

1191. WxLogic 1:51 AM GMT en Agosto 25, 2009
Quoting kmanislander: This year is starting to feel more and more like 2004. Sort of quiet out of the gate and then 8 weeks of hyper activity. The heat in the Caribbean has been unbelievable. High 90's most days with a heat index near 115 F. Very little rain. Hurricanes are nature's way of transferring high heat from the tropics to places far N. I can't believe that the season will limp to a finish the way it has started. Ohh yeah... the Carib and GOM are over due for their heat transfer... it if doesn't get transferred now... it will sure get transfer in the form of SVR WX in the winter. Member Since: Agosto 14, 2008 Posts: 4 Comments: 4721

1193. litestar 1:52 AM GMT en Agosto 25, 2009
Keeper of the gate are you there?

1194. TexasHurricane 1:52 AM GMT en Agosto 25, 2009
Quoting WxLogic: Ohh yeah... the Carib and GOM are over due for their heat transfer... it if doesn't get transferred now... it will sure get transfer in the form of SVR WX in the winter. What does that mean? Member Since: Julio 2, 2009 Posts: 0 Comments: 2811

1195. AllStar17 1:53 AM GMT en Agosto 25, 2009
Quoting extreme236: Were not talking about now, were talking about Wednesday. You are right! A TD by Wednesday is certainly not out of the question. Member Since: Junio 29, 2009 Posts: 13 Comments: 5145

1197. hydrus 1:53 AM GMT en Agosto 25, 2009
Quoting atmoaggie: Watch that movie a couple of times? And, Dr. M, and I am sure a few others, made mention of a coming quiet period. Previous post went the Japanese small engine repair blog, I guess. (Sorry if doubles) Whatever is going on out there,you guys are always on top of the latest info.That is why if something looks like trouble or imminent I come here rather then TWC or CNN. Member Since: Septiembre 27, 2007 Posts: 1 Comments: 14721

1198. AllStar17 1:54 AM GMT en Agosto 25, 2009
Quoting StormW: Actually...it's a photo that one of your only two friends sent me. Careful Storm, we do not want you getting banned. Member Since: Junio 29, 2009 Posts: 13 Comments: 5145

1200. extreme236 1:55 AM GMT en Agosto 25, 2009
Quoting canesrule1: hmmmmm: Uh thats the current shear map. Member Since: Agosto 2, 2007 Posts: 19 Comments: 19234

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