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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1601. GatorWX 1:33 PM GMT on August 25, 2009
93L looks impressive, but I'm afraid it's time is numbered Member Since: January 1, 2008 Posts: 0 Comments: 651

1602. KEEPEROFTHEGATE (Mod) 1:35 PM GMT on August 25, 2009
I got to go get some stuff done check back in at noon when iam on lunch later all Member Since: July 15, 2006 Posts: 147 Comments: 41332

1603. laflastormtracker 1:36 PM GMT on August 25, 2009
Models picking up on the affect of the high pressure currently to its Northeast?

1604. largeeyes 1:37 PM GMT on August 25, 2009
These models are worthless until there is SOME sort of COC. Kepper, those lines are dead straight, so not even a hint really. Member Since: August 22, 2006 Posts: 0 Comments: 1383

1605. NEwxguy 1:38 PM GMT on August 25, 2009
If 92L doesn't slow down it will get swept out to sea. Member Since: September 6, 2007 Posts: 820 Comments: 13283

1606. largeeyes 1:39 PM GMT on August 25, 2009
IKE, and another chance for me to embarass myself trying to surf. WOot! Member Since: August 22, 2006 Posts: 0 Comments: 1383

1607. OSUWXGUY 1:39 PM GMT on August 25, 2009
Good Morning Everyone! Looks like 92L is improving in organization in spite of 30 knots of southerly shear... Now the 850/700mb vorticity, surface convergence and upper level divergence are all co-located. In addition to the shear, the strong low/mid level flow driven by the strong pressure gradient between the Bermuda High and 92L will make it difficult for the circulation to close off on the west side. There are decent southerlies on the east side and very strong easterlies to the north, but no signs of northerlies or westerlies in the western half of the circulation.

1608. KEEPEROFTHEGATE (Mod) 1:40 PM GMT on August 25, 2009
Quoting NEwxguy: If 92L doesn't slow down it will get swept out to sea. thats a good thing Member Since: July 15, 2006 Posts: 147 Comments: 41332

1609. NEwxguy 1:41 PM GMT on August 25, 2009
Quoting KEEPEROFTHEGATE: thats a good thing Yes, a very good thing! Member Since: September 6, 2007 Posts: 820 Comments: 13283

1610. tbonehfx 1:41 PM GMT on August 25, 2009
Quoting FloridaTigers: Wait, Europe NAMES their highs and lows? What a silly practice. It is what it is. I guess it makes tracking and discussion simpler, especially for laypeople. European windstorm names Member Since: October 8, 2005 Posts: 0 Comments: 37

1611. Engine2 1:42 PM GMT on August 25, 2009
Quoting NEwxguy: Yes, a very good thing! An extremely good thing Member Since: February 27, 2006 Posts: 0 Comments: 482

1612. TheCaneWhisperer 1:42 PM GMT on August 25, 2009
21.7? What am I missing? This image is only an hour and 40 minutes old.

1613. serialteg 1:43 PM GMT on August 25, 2009
Africa-Atlantic trying to spin up Member Since: August 22, 2006 Posts: 2 Comments: 1967

1614. kanc2001 1:44 PM GMT on August 25, 2009
Quoting FloridaTigers: Wait, Europe NAMES their highs and lows? What a silly practice. most of New england names winter storms Member Since: August 18, 2008 Posts: 0 Comments: 181

1615. IKE 1:45 PM GMT on August 25, 2009
Quoting TheCaneWhisperer: 21.7? What am I missing? This image is only an hour and 40 minutes old. Look at the floater on 92L. There's nothing at 19.5N and 63.5W. Member Since: June 9, 2005 Posts: 23 Comments: 37070

1616. IKE 1:46 PM GMT on August 25, 2009
Member Since: June 9, 2005 Posts: 23 Comments: 37070

1617. Gumbogator 1:47 PM GMT on August 25, 2009
NW flow and low 60 temps @ night, in the middle of hurricane season. El Nino has torn up the East Coast this yr. Cold fronts keep coming and are lead blockers against any storm trying to landfall in the U.S. Danny should form by late Thursday = fish ?? Member Since: August 21, 2008 Posts: 0 Comments: 97

1618. Elena85Vet 1:47 PM GMT on August 25, 2009
Quoting kanc2001: most of New england names winter storms Mr. Freeze? Member Since: August 18, 2008 Posts: 0 Comments: 619

1619. OSUWXGUY 1:49 PM GMT on August 25, 2009
Quoting TheCaneWhisperer: 21.7? What am I missing? This image is only an hour and 40 minutes old. Not sure you're missing anything... First of all, I don't agree with a closed low. Second, I think the ~22°N 63.5°W area is where the best convergence and vorticity are located.

1620. largeeyes 1:49 PM GMT on August 25, 2009
Most of those names can't be repeated in a public forum when the mods are looking though. Member Since: August 22, 2006 Posts: 0 Comments: 1383

1622. LightningCharmer 1:52 PM GMT on August 25, 2009
Quoting tbonehfx: It is what it is. I guess it makes tracking and discussion simpler, especially for laypeople. European windstorm names Interesting bit of weather trivia. Thanks. Member Since: September 1, 2007 Posts: 0 Comments: 1111

1623. VAbeachhurricanes 1:54 PM GMT on August 25, 2009
Member Since: September 6, 2007 Posts: 0 Comments: 4883

1624. nrtiwlnvragn 1:54 PM GMT on August 25, 2009
Quoting mikatnight: Noticed the CMC says "not available"...NOGP and a couple others missing too from that... Missing global models do not develop the circulation and thus do not show a track. Maybe the 12Z with a little stronger system (25 Kt init) will be able to hang on to the circulation. One other thing to note, the TVCN is offset to the left. That is the influence of the EMX (ECMWF) which the NHC does not release the data on. Member Since: September 23, 2005 Posts: 12 Comments: 9095

1626. serialteg 1:57 PM GMT on August 25, 2009
Considering European highs - and lows - can produce 40ft seas and stuff, I wouldn't be surprised... Member Since: August 22, 2006 Posts: 2 Comments: 1967

1627. largeeyes 1:59 PM GMT on August 25, 2009
92l seems so far from being organized. How is it red? Member Since: August 22, 2006 Posts: 0 Comments: 1383

1628. Quadrantid 2:00 PM GMT on August 25, 2009
First time poster here -- though I've been reading for a couple of years :) It's getting a bit showery and damp here in the UK (big surprise) ahead of the remains of Bill - so I was nosying at the metoffice IR plot (http://www.metoffice.gov.uk/satpics/latest_IR.html), and noticed the storm appeared to split in half on its way across the atlantic - one bit heading to us, and one bit heading south past Spain. Anyone got any idea what happened? Apologies if it is a noob question :D Member Since: June 13, 2009 Posts: 0 Comments: 104

1629. PensacolaDoug 2:01 PM GMT on August 25, 2009
Quoting mikatnight: An even sillier practice is letting mass murderers go free. We should boycott all products from those miserable bastards. I know how ya feel. Member Since: July 25, 2006 Posts: 0 Comments: 4832

1630. Autistic2 2:02 PM GMT on August 25, 2009
Quoting mikatnight: An even sillier practice is letting mass murderers go free. We should boycott all products from those miserable bastards. 270 dead and one free over prostate cancer? What's that woth for the price of oil to England. Do red circles ever just go Poof, or do they usally develop. I don't thin the NHC used cirles last year? Member Since: August 29, 2008 Posts: 0 Comments: 307

1631. PensacolaDoug 2:02 PM GMT on August 25, 2009
Blue Angels are up and at it here on the west side this morning! Member Since: July 25, 2006 Posts: 0 Comments: 4832

1632. SeVaSurfer 2:03 PM GMT on August 25, 2009
Quoting VAbeachhurricanes: YIKES! Member Since: August 30, 2006 Posts: 0 Comments: 104

1633. PensacolaDoug 2:04 PM GMT on August 25, 2009
Cyclone Oz will be home today. I can't wait to see his video! Member Since: July 25, 2006 Posts: 0 Comments: 4832

1634. bingcrosby 2:04 PM GMT on August 25, 2009
The CMC model really likes 92L. Member Since: August 14, 2008 Posts: 0 Comments: 137

1635. NEwxguy 2:04 PM GMT on August 25, 2009
The big question to determine the track of 92L is when the trough moves through us here in the northeast thurs. and friday,up into northeast Canada,and a block occurs,will the trough predicted to form in the midwest cause it to move north rather than out to sea.Too many questions at this point. Member Since: September 6, 2007 Posts: 820 Comments: 13283

1636. mikatnight 2:07 PM GMT on August 25, 2009
Quoting PensacolaDoug: Blue Angels are up and at it here on the west side this morning! Up, up, and away! Member Since: October 18, 2005 Posts: 3 Comments: 2194

1637. homelesswanderer 2:07 PM GMT on August 25, 2009
Good Morning! Looks like TX didn't get the cooler dryer memo. Lol. But we'll take the troughs. Keep 'em comin' Mother Nature. :) 81 °F Partly Cloudy Humidity: 74% Dew Point: 72 °F Wind: 8 mph from the ENE Pressure: 30.03 in (Rising) Heat Index: 85 °F Visibility: 8.0 miles UV: 2 out of 16 Clouds: Few 7000 ft (Above Ground Level) Elevation: 13 ft Member Since: August 15, 2008 Posts: 10 Comments: 3665

1638. Chicklit 2:09 PM GMT on August 25, 2009
Quoting IKE: Look at the floater on 92L. There's nothing at 19.5N and 63.5W. Loop Member Since: July 11, 2006 Posts: 14 Comments: 10382

1639. crownwx 2:10 PM GMT on August 25, 2009
Quoting StormW: I think a COC will be closer to where TCW has that graphic posted. Closer to 19.4 North/63.6 West Storm? Member Since: December 27, 2004 Posts: 3 Comments: 207

1640. nrtiwlnvragn 2:12 PM GMT on August 25, 2009
Preliminary Extended Forecast Discussion THE PROBLEM OF THE DAY CONTINUES TO BE A DEVELOPING TROPICAL DISTURBANCE...NOW NEAR 21.5N 61.5W...WHICH CONTINUES TO EXHIBIT DIFFERENCES AND DAY-TO-DAY CHANGES WITHIN THE MEDIUM RANGE GUIDANCE. ALL THE GLOBAL GUIDANCE HAVE TRENDED WESTWARD WITH ITS TRACK SINCE THIS TIME YESTERDAY WHILE THEIR FORWARD MOTION HAS SHOWN GOOD CONTINUITY. HOWEVER...THE 00Z MULTI-MODEL ENSEMBLE GUIDANCE SHOWS THE ECMWF MEMBERS MORE WEST/INLAND THAN THE CANADIAN/GEFS MEMBERS WHICH ARE OFFSHORE. THE NON-ETA 03Z SREF MEMBERS ALSO PREFER AN OFFSHORE TRACK WHILE THE ETA MEMBERS HEAD THE POSSIBLE TROPICAL CYCLONE TOWARDS THE CAROLINAS. CHOSE TO SPLIT THE DIFFERENCE IN THE ENSEMBLE SPREAD AND TRACK THE SYSTEM CLOSE TO THE EASTERN SEABOARD...WHICH LED TO ADDITIONAL ACCELERATION FROM THE NIGHT SHIFT PROGS. THIS PREFERRED SOLUTION MIRRORS A SLIGHTLY SLOWER VERSION OF THE 06Z DGEX WITH THIS CYCLONE. HEAVY RAINFALL SHOULD SPREAD TO THE LEFT OF ITS TRACK ALONG THE MID-ATLANTIC COAST THROUGH SOUTHERN AND EASTERN NEW ENGLAND...IF THIS TRACK VERIFIES. THE COORDINATION CALL WITH TPC AT 16Z SHOULD BE INTERESTING TODAY...AND COULD LEAD TO CHANGES IN THIS PREFERENCE. Preliminary Graphics Member Since: September 23, 2005 Posts: 12 Comments: 9095

1641. TriniGirl26 2:13 PM GMT on August 25, 2009
new blog out Member Since: August 18, 2009 Posts: 0 Comments: 201

1642. largeeyes 2:13 PM GMT on August 25, 2009
Angels buzzed our factory in a starburst once. We made the generators for the F-18E/F and C/D. Member Since: August 22, 2006 Posts: 0 Comments: 1383

1643. tbonehfx 2:13 PM GMT on August 25, 2009
Quoting kanc2001: most of New england names winter storms Here in Nova Scotia, we had a massive nor'easter about 4 months after Hurricane Juan hit us in 2003. Lots of snow 38+" in 36 hours and winds gusting to 140 km/h. The local media somehow got to calling it "White Juan". Which strikes me as funny.. does that make the hurricane "Brown Juan"? Member Since: October 8, 2005 Posts: 0 Comments: 37

1644. Murko 2:14 PM GMT on August 25, 2009
Quoting mikatnight: An even sillier practice is letting mass murderers go free. We should boycott all products from those miserable bastards. Don't be an idiot, what use is that going to be? I don't agree that he should have been released, but it was their decision and their law that allowed it. Why don't we boycott US goods for funding the IRA? M Member Since: July 13, 2007 Posts: 0 Comments: 129

1645. LightningCharmer 2:15 PM GMT on August 25, 2009
. Member Since: September 1, 2007 Posts: 0 Comments: 1111

1646. PensacolaDoug 2:44 PM GMT on August 25, 2009
Sounds like yer trollin to me Murky. Member Since: July 25, 2006 Posts: 0 Comments: 4832

1647. TampaSpin 2:51 PM GMT on August 25, 2009
Just completed a Tropical Update as conditions are improving for 92L. New Interests in the Central Atlantic and moving off the coast of Africa. Watch the GOM from the stalled front also! Member Since: September 2, 2007 Posts: 176 Comments: 19767

1648. ManicouRiverResort 6:27 PM GMT on June 13, 2010
I am in Dominica - Windward Isles. Hope that 92 fizzles out. 50% sounds high chance though. I will keep in touch if it gets nasty. Too early is the season for that surely? Still the water has been especially warm here since March. Member Since: March 19, 2010 Posts: 35 Comments: 27

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