Bill intensifies to Category 4; globe has 5th warmest July on record

By: Dr. Jeff Masters , 3:28 PM GMT on August 19, 2009

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Category 4 Hurricane Bill is now the the fourth strongest tropical cyclone to appear on the planet so far this year, and may grow even stronger. Visible and infrared satellite imagery continue to show an impressive, well-organized, hurricane, with plenty of low-level spiral banding and upper-level outflow well-established on all sides except the west. On Bill's west side, upper-level winds from the west are creating a modest 10 knots of wind shear, which is giving the hurricane a bit of a squashed appearance there.

Wind shear is forecast to remain low to moderate, 5-15 knots, for the next four days. Sea Surface Temperatures (SSTs) will rise steadily from 28.5°C today to 29°C on Friday. Total ocean heat content is at a maximum today, and will gradually decline over the next four days. Bill should be able to take advantage of these favorable conditions a remain a major hurricane the next three days.


Figure 1. Visible satellite image from NASA's Aqua spacecraft at 12:40pm EDT Tuesday August 18, 2009. Image credit: NASA GSFC.

Water vapor satellite loops show a small "short-wave" trough of low pressure to the north-northwest of Bill, and this trough has turned Bill on a more northwesterly track over the past two days. Bill will miss the Lesser Antilles Islands, and the main impact of the hurricane on these islands will be high waves. The short wave trough (so called because it has a relatively small amplitude and wavelength) is not strong enough to turn Bill due north, and Bill is also expected to miss Bermuda. High waves and sustained winds of 20 - 30 mph are the worst that Bermuda is likely to get from Bill.


Figure 2. Visible satellite image of Bill's eye zoomed in, taken from NASA's Aqua spacecraft at 12:40pm EDT Tuesday August 18, 2009. Image credit: NASA GSFC.

An unusually strong "long wave" trough of low pressure (called long wave because of its large amplitude and wavelength) is expected to develop along the U.S. East Coast late this week. This trough will turn Bill to the north, and also bring high levels of wind shear in the 40 - 65 knot range on Sunday. Exactly where this turn occurs is still not clear. The models continue to be in two camps: an eastern camp (GFS, GFDL, HWRF, and ECMWF) that takes Bill 300 - 500 miles east of Cape Cod, and a more western camp (NOGAPS, UKMET) that bring Bill within 150 - 200 miles of Cape Cod. Both sets of models bring Bill ashore over the Canadian provinces of Newfoundland or Nova Scotia. Bill will be weakening rapidly as it makes landfall, and is likely to be a Category 1 hurricane if it hits Nova Scotia, or strong tropical storm if it hits Newfoundland.

Bill's big waves
Large swells from Bill will begin impacting the U.S. East coast from Florida to Maine beginning Friday night or Saturday morning. Seas will build to 5 - 10 feet in the offshore waters from central Florida northwards to South Carolina, and to 10 - 15 feet from North Carolina to Cape Cod. Near shore, waves will be about 40% less. This will cause a significant coastal erosion event along some portions of the coast. The latest run of the NOAA Wavewatch III model suggests that significant wave heights near Bill's center will reach 50 feet on Sunday. Since maximum wave height is typically about a factor of 1.9 greater than the significant wave height (which is the average trough-to-crest height of the top 1/3 largest waves), a few huge waves near Bill's center may reach 95 feet high.

Possible impacts to New England
The current set of computer model runs predicts that the center of Bill will pass Cape Cod, Massachusetts Sunday afternoon or evening. Tropical storm-force sustained winds of 39 mph or greater currently extend out 185 miles to the west of Bill's center, so that if Bill maintains its current wind distribution, Cape Cod could see sustained winds of about 40 mph Sunday night if the models predicting a more westerly path are correct. However, Bill will not keep this same radius of winds. The hurricane will weaken considerably beginning Sunday morning, once the storm gets caught up in the approaching long wave trough. High wind shear of 40 - 65 knots due to strong southwesterly winds aloft will act to compress the hurricane in the east-west direction, keeping the hurricane's strongest winds away from Cape Cod. The highest winds are likely to be no more than 30 mph on Cape Cod from Bill, if the storm follows the track of the western camp of models nearest to the Massachusetts. A few rain squalls may affect coastal Massachusetts, but the main impact of Bill on New England is likely to be coastal erosion from high waves.

Elsewhere in the tropics
The remains of Tropical Storm Ana are bringing scattered heavy rain showers to the Bahamas and Florida today. The remains are disorganized, and are not likely to re-develop. The only model calling for a new tropical cyclone to develop in the Atlantic over the next seven days is the GFS model, which predicts development off the coast of Africa about 7 days from now.

Fifth warmest July on record globally; a cold July in the U.S.
The globe recorded its fifth warmest July since record keeping began in 1880, according to NOAA's National Climatic Data Center. NOAA rated the period January - July 2009 as the sixth warmest such period on record. NASA's Goddard Institute for Space Studies rated July 2009 as the 2nd warmest July on record, behind July of 1998. For the second month in a row, global ocean Sea Surface Temperatures (SSTs) in July were the warmest on record, 0.59°C (1.06°F) above the 20th century average. This broke the previous July record set in 1998. The record July SSTs were due in part to an ongoing El Niño event in the Eastern Pacific, which has substantially warmed a large stretch of the tropical Eastern Pacific Ocean. As El Niño conditions mature during the coming months, near-record global ocean and land temperatures will probably continue. Now that El Niño conditions have been well-established for three months, the atmosphere has begun to heat up in response. It typically takes up to seven months for the atmosphere to heat up in response to ocean heating from an El Niño. This may explain why June of 2009, which independent assessments by NOAA, NASA, and the UK Hadley center agreed was the 2nd or 3rd warmest June on record at the surface, recorded only average satellite-measured temperatures in the lower atmosphere. In contrast, the July satellite-measured temperatures in the lower atmosphere were the 2nd or 3rd warmest on record, in agreement with the assessments that surface temperatures were the 2nd to 5th warmest on record.


Figure 3. Departure of temperature from average for July 2009. Image credit: NOAA/NCDC.

A cold July for the U.S.
For the contiguous U.S., the average July temperature of 23.1°C (73.5°F) was the coolest since 1994, and July temperatures were the 27th coolest in the 115-year record, according to the National Climatic Data Center. Ohio, Illinois, Indiana, Pennsylvania, Iowa, and West Virginia experienced their coolest ever July. Kentucky, Missouri, Michigan, and Wisconsin recorded their second coolest July in history. A strong trough of low pressure parked itself over the eastern portion of the U.S. in July, funneling down plenty of cold air from Canada. In the western U.S., a ridge of high pressure dominated, bringing unusually hot conditions. Arizona recorded its 3rd warmest July on record, and Seattle, Washington recorded its hottest day in history on July 28, notching a 103°F reading. This was 3°F above the previous record set in 1994.

U.S. precipitation was near average in July, with the month ranking 40th wettest in the 115-year record. U.S. tornado activity was above average in July, according to NOAA's Storm Prediction Center. However, no tornado deaths occurred in July.

At the end of July, 14% of the contiguous United States was in moderate-to-exceptional drought. This is a drop from the 19% figure observed at the beginning of the year. These extreme drought regions were exclusively in South and Central Texas.

I'll have an update Thursday morning.

Jeff Masters

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Quoting apocalyps:


I disagree,every day the models have taken Bill a little closer to the Eastcoast.
If this lasts one more day there is something going to be hit.
I agree almost every day the models are moving around and especialy the Ensemble models. They're predicting a New England landfall.
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According to the latest NHC track, Bill is supposed to track directly North between 30N and 40N correct? I will believe it when I see it.
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Thanks very much 1999. breald
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2069. IKE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAUNTON MA
605 AM EDT THU AUG 20 2009

.SYNOPSIS...
-- Changed Discussion --
VERY WARM AND HUMID WEATHER WILL CONTINUE INTO AT LEAST SATURDAY AS
HIGH PRESSURE OFFSHORE COMBINES WITH LOW PRESSURE NEAR THE GREAT
LAKES TO YIELD A PERSISTENT SOUTHWESTERLY FLOW ACROSS NEW ENGLAND.
THIS WEATHER PATTERN WILL BE ACCOMPANIED BY ISOLATED SHOWERS AND
THUNDERSTORMS THIS AFTERNOON AND TONIGHT...THEN BECOMING MORE
NUMEROUS FRIDAY AFTERNOON INTO SATURDAY AS A TROUGH OF LOW PRESSURE
APPROACHES FROM THE WEST. THE PROJECTED TRACK OF HURRICANE BILL
STILL APPEARS TO BE WELL EAST OF NANTUCKET SOMETIME SUNDAY. ITS MAIN
EFFECTS ON SOUTHERN NEW ENGLAND WILL BE IN THE FORM OF HIGH SURF AND
DANGEROUS RIP CURRENTS TO OCEAN BEACHES BEGINNING LATE FRIDAY AND
CONTINUING THROUGH THE WEEKEND.



Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting breald:


I am watching it. I am just not going to get all panicky just yet. Things could change but the models seem to be the same they were 3 days ago. Pretty consistent.


I disagree,every day the models have taken Bill a little closer to the Eastcoast.
If this lasts one more day there is something going to be hit.
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Quoting BGMom:
Hello all - I asked a question before, and couldn't figure out how to find it. So much activity on the blog! It got buried. I was asking about how Bill might affect weather just northwest of Atlanta - if at all. And does the pollution shove rain away?
Anyway - I am writing now to voice irritation with a newscaster on tv today. After reading everything y'all have said - and how nothing is ever certain, this weather person blew off Bill with absolute certainty.
"Good news! Bill is an exciting storm - I like a good hurricane - but everyone is in the clear. It's going to miss the Bahamas, the East coast -" blah blah blah -- but she presented it as a "for sure."
Irritating.
My understanding (from this blog, and the Tropical Weather Discussion) is that nothing is written in stone for New England (and NY for that matter), and that Eastern Canada is very much at risk. Looks pretty clear for the rest of us.
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2065. breald
Quoting Category5hitsNewYork:

You guys are too lenient. Can you at least say that Bill is still a threat and it is unpredictable where he will go. We need watch it before we can say that the forecast will verify.
Don't let your guard down


I am watching it. I am just not going to get all panicky just yet. Things could change but the models seem to be the same they were 3 days ago. Pretty consistent.
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Quoting P451:
So many models, generally so much agreement. Pretty fascinating actually.

Most of those tracks on that chart are a little farther westward than the forcasted track.
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Thanks for the info!!

I kind of feel a little bit relieved, but I have till later today to cancel my trip so I will check back with you guys later to get an update..till then, thanks.

appreciate your comments.
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2060. breald
Quoting marknmelb:


I remember when I sent my wife a pic of the first track showing Jeane looping back to hit us. She said "Not very f'in funny. How did I make that pic?" I told her it was really the official track. A few days later 30% more of my shingles were all over the yard ....


Wasn't Jeanne thew one that did all kinds of loops and turn before it move ashore?
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Quoting breald:


You should be fine.

I think I will take a drive to the beach this weekend to see these huge waves.


With Bill going WNW today i dont think you will.
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2057. breald
Quoting justalurker:
morning all,

I have a business trip set up for this weekend in NY and Boston, my question, should i cancel my trip or proceed? and what percentage of striking that area now?


You should be fine.

I think I will take a drive to the beach this weekend to see these huge waves.
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Quoting TheCaneWhisperer:


Just like Hurricane Jeanne was surely going out to sea. The models were in great agreement on that until the pesky NoGaps picked up on the loop.


I remember when I sent my wife a pic of the first track showing Jeane looping back to hit us. She said "Not very f'in funny. How did I make that pic?" I told her it was really the official track. A few days later 30% more of my shingles were all over the yard ....
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2052. IKE
Quoting justalurker:
morning all,

I have a business trip set up for this weekend in NY and Boston, my question, should i cancel my trip or proceed? and what percentage of striking that area now?


AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
751 AM EDT THU AUG 20 2009

.SYNOPSIS...
A WARM FRONT WILL REMAIN OVER THE NORTHERN PORTIONS OF THE TRI-
STATE AREA TODAY. AN UPPER TROUGH TO OUR NORTHWEST WILL PUSH A
STRONG FRONT INTO THE REGION FRIDAY NIGHT INTO SATURDAY. THIS
FRONT IS EXPECTED TO KEEP MOST IMPACTS OF HURRICANE BILL TO OUR
EAST.
SUNDAY THROUGH TUESDAY SHOULD BE DRIER BEHIND THE UPPER
TROUGH.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
2049. P451
Great graphic.
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Quoting justalurker:
morning all,

I have a business trip set up for this weekend in NY and Boston, my question, should i cancel my trip or proceed? and what percentage of striking that area now?


And the eye is shrinking.Putting his act together.
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morning all,

I have a business trip set up for this weekend in NY and Boston, my question, should i cancel my trip or proceed? and what percentage of striking that area now?
Member Since: Posts: Comments:
Quoting BGMom:
Hello all - I asked a question before, and couldn't figure out how to find it. So much activity on the blog! It got buried. I was asking about how Bill might affect weather just northwest of Atlanta - if at all. And does the pollution shove rain away?
Anyway - I am writing now to voice irritation with a newscaster on tv today. After reading everything y'all have said - and how nothing is ever certain, this weather person blew off Bill with absolute certainty.
"Good news! Bill is an exciting storm - I like a good hurricane - but everyone is in the clear. It's going to miss the Bahamas, the East coast -" blah blah blah -- but she presented it as a "for sure."
Irritating.


Just like Hurricane Jeanne was surely going out to sea. The models were in great agreement on that until the pesky NoGaps picked up on the loop.
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Bill is getting better Sully. His outflow is improving to the NW quadrant. Convection is strongest on the north side of the eyewall and the southern side is weak at best. I think he strengthens to a 150mph storm with a pressure in the 925 to 935 range.
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2044. IKE
Quoting K8eCane:
thank you Ike
thats what i was looking for was the actual miles
local mets aint even saying the actual miles
again thank you



AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
658 AM EDT THU AUG 20 2009

.SYNOPSIS...
BERMUDA HIGH PRESSURE REMAINS NEARLY STATIONARY OFF THE SOUTHEAST
UNITED STATES COAST THROUGH FRIDAY. A SLOW MOVING FRONTAL BOUNDARY
WILL APPROACH THE AREA FROM THE WEST FRIDAY NIGHT...THEN PUSH ACROSS
THE AREA SATURDAY INTO SUNDAY. HURRICANE BILL WILL PASS SEVERAL
HUNDRED MILES EAST OF THE MID ATLANTIC COAST LATE SATURDAY THROUGH
SUNDAY.

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting sullivanweather:
As expected, Bill weakened overnight to a cat 3 storm. However, this weakening is only temporary. The inner core of the storm is starting to reorganize itself and cloud tops have started to cool once again. It appears the storm is coming into another area of excellent upper level diffluence and I fully expect a second peak in intensity tonight somewhere in the 150mph/935mb range.


Indeed and add a more western track to all models.Today Bill is going WNW.
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The water temperature to the north and west of Bill is higher than anything he's been through so far, and it stays as warm for quite a long way north.


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As expected, Bill weakened overnight to a cat 3 storm. However, this weakening is only temporary. The inner core of the storm is starting to reorganize itself and cloud tops have started to cool once again. It appears the storm is coming into another area of excellent upper level diffluence and I fully expect a second peak in intensity tonight somewhere in the 150mph/935mb range.
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2040. BGMom
Hello all - I asked a question before, and couldn't figure out how to find it. So much activity on the blog! It got buried. I was asking about how Bill might affect weather just northwest of Atlanta - if at all. And does the pollution shove rain away?
Anyway - I am writing now to voice irritation with a newscaster on tv today. After reading everything y'all have said - and how nothing is ever certain, this weather person blew off Bill with absolute certainty.
"Good news! Bill is an exciting storm - I like a good hurricane - but everyone is in the clear. It's going to miss the Bahamas, the East coast -" blah blah blah -- but she presented it as a "for sure."
Irritating.
Member Since: Posts: Comments:
2039. K8eCane
thank you Ike
thats what i was looking for was the actual miles
local mets aint even saying the actual miles
again thank you
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2037. Ossqss



They still like the CV potential.
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2035. IKE
Quoting K8eCane:
not in any way shape or form to discount any other areas potentially in harms way- but am i correct in assuming that the models are much closer to WILMINGTON NC dammit!


No....at least 300 miles east of NC.....
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting cajunmoma:


Im just hoping Bill stays away...far far away!!


Amen to that!!
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Have to get ready for work now. Thanks for all the help guys, I am still learning, and when you guys answer my questions, it definately help. Thanks Again, and everyone have a good day!!!
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2030. K8eCane
not in any way shape or form to discount any other areas potentially in harms way- but am i correct in assuming that the models are much closer to WILMINGTON NC dammit!
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Good loop to view the overall situation. Select the Trop Fcst Pts and NCEP Fronts. You can see the trough in the midwest and Bill.
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2026. Ossqss
Hey Aussie, here is what I found. Cheers to you with coffee in hand. LoL

Back to Basic Definitions Page | Back to Main FAQ Page

Subject: A3) What is a super-typhoon? What is a major hurricane ? What is an intense hurricane ?
Contributed by Stan Goldenberg




"Super-typhoon" is a term utilized by the U.S. Joint Typhoon Warning Center for typhoons that reach maximum sustained 1-minute surface winds of at least 65 m/s (130 kt, 150 mph). This is the equivalent of a strong Saffir-Simpson category 4 or category 5 hurricane in the Atlantic basin or a category 5 severe tropical cyclone in the Australian basin.

"Major hurricane" is a term utilized by the National Hurricane Center for hurricanes that reach maximum sustained 1-minute surface winds of at least 50 m/s (96 kt, 111 mph). This is the equivalent of category 3, 4 and 5 on the Saffir-Simpson scale.

"Intense hurricane" is an unofficial term , but is often used in the scientific literature. It is the same as "major hurricane".

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Quoting NY2FLTransplant:


You are right, of course. It scares me a bit too--should have put that in my first post! My family still lives on Long Island, near the north shore, but not that close to the coast. Obviously, the north shore doesn't get it as bad as the south shore since the land mass would likely slow Bill down considerably.

If all goes well with the current track, they won't feel more than some gusty winds...but it is something I am keeping my eye on, because it would simply be a monumental task--in my opinion impossible--to evacuate that many people when there are only a few ways off of the island.


Im just hoping Bill stays away...far far away!!
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Quoting stormsurge39:
Ive noticed on Bills track, that he is going more degrees longitude than latitude. Its confusing that he going more W than N and is on a NW track, seems like it would be the other way around. Oh well just an observation.


A true NW track would mean he travelled the same distance west as north. Most of his track has been roughly WNW, which means 2 miles west for each mile north.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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