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 atmoaggie:

...unless it were to be strong enough to advect vorticity from some other, nearby feature. Happens. (But I do not see that being the case with Ana-wave)


Certainly, but with the wave formerly known as Ana you are correct...
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FloodMan as you can tell i didnt understand,but i got your point now. Thanks
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Quoting TriniGirl26:
Quoting pearlandaggie:
Do we have any friends on the blog that live in the Antilles?

Don't Know if i count. I'm from Trinidad...lol..party cloudy here...expecting rain in about 30 mins.
Hey Trinigirl i'm from Barbados
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Quoting StormW:


Crap.


I confused. Crap as in oh darn or crap as in not true.
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I'm hoping the approaching cold front will produce some good T-Storms here! Conditions are right.

Maritimes BE PREPARED!
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Quoting Floodman:


You're missing my point: the 850 mb vorticity IS the LLC for the storm; no vorticity at 850, no low level circulation. The 850mb vorticity can't strengthen the storm, it IS the storm. If something else strengthenms the storm the vorticity at that level (and lower even) can strengthen, but the vorticity is a function of the strengthening, not the element that strengthens it

...unless it were to be strong enough to advect vorticity from some other, nearby feature. Happens. (But I do not see that being the case with Ana-wave)
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Quoting StormW:


Crap.

Good way to put it, Storm! Pretty much my sentiments, especially if the GFS forecast pans out past 7 days.
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@152 thank you for the clarification Dr Masters. Perhaps something to include in the next blog update.
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Quoting IKE:


Look at the water vapor loop I just posted. Trough is not weak...


That is part of the trough, but the "kicker" part is just developing. Single step through HPC's 7 Day Surface Analysis. The main part comes out of North Dakota, which you can see starting looking at Western U.S. - Water Vapor Loop
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Quoting BayouBorn1965:
I believe the Father's Almanac got the storm activity right this time around. It was waaay off for Katrina, but believe it's right for Bill. If that is the case, the Gulf Coast might have to get ready for September. Got my plywood!


I realize that it may be wrong, but what does it say for September?
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Quoting Melagoo:


Good loop of entire Atlantic Africa too!


I don't like the look of that HWRF, it has bill staying over warm water longer and puts St. John's into the eastern Eyewall.
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Quoting stormsurge39:
So Floodman can that help developement?


You're missing my point: the 850 mb vorticity IS the LLC for the storm; no vorticity at 850, no low level circulation. The 850mb vorticity can't strengthen the storm, it IS the storm. If something else strengthenms the storm the vorticity at that level (and lower even) can strengthen, but the vorticity is a function of the strengthening, not the element that strengthens it
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Quoting StormW:
Are we still debating the busting of the trof by a hurricane? Doesn't matter if the NHC predicts that occurence or not...what my MAIN point was...it's possible!

Sheesh!!


Uhh, yes it does matter if the NHC predicted it. It means that it's not some random, unpredictable thing that could happen to Bill without warning, like some of the doom/wishcasters seem to want. It's a phenomenon that the models are able to predict...
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158. slavp
Quoting CaneWarning:


Please share this crap with me... I'm not getting it. :)
I am no expert, but I think it means there is a lot of MoJO out there for possibility of increased activity
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Comparing 06Z GFS to 12Z GFS

06Z GFS


12Z GFS


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Quoting StormW:
Are we still debating the busting of the trof by a hurricane? Doesn't matter if the NHC predicts that occurence or not...what my MAIN point was...it's possible!

Sheesh!!

Yea well, some people.
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Quoting StormW:


Hey aggie...tis not a good thing...'specially when it's in Octants 1 or 2.


Can you be a little more specific on this?? How bad is that or would that be?
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Good loop of entire Atlantic Africa too!
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152. JeffMasters (Admin)
Quoting rwdobson:
Interesting video...apparently, though, this trough-breaking was predicted well in advance by NHC and the models.


A hurricane can break through a short wave trough or upper-level cold low, although the passage will weaken it. A hurricane cannot break through a major long wave trough like the one approaching Bill this weekend. In some cases, a long wave trough will move too quickly or not extend far enough south to fully recurve a hurricane, leaving the hurricane behind after the trough passes. That will not be the case with this weekend's trough, which is unusually strong will reach unusually far south for this time of year.

Jeff Masters
I believe the Father's Almanac got the storm activity right this time around. It was waaay off for Katrina, but believe it's right for Bill. If that is the case, the Gulf Coast might have to get ready for September. Got my plywood!
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150. srada
Quoting OSUWXGUY:


The intense outflow from Bill is forecast by the GFS (and other models) to help enhance the ridging to its northeast as the outflow sinks and dries/warms the air.

Essentially there will be a squeeze play between this stronger riding to the east and north of Bill and the strong trough to the west.

Bill's influence may be to slow the trough down a bit, which won't prevent it from recurving (as the ridging to its east is oriented too North/South)


Thanks!
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Quoting atmoaggie:

I concur with your crap.


Please share this crap with me... I'm not getting it. :)
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Posted by: JeffMasters, 3:28 PM GMT on August 19, 2009
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.

- - - - - -
Typhoon Vamco might will be up there with Bill soon. Loop shows a very small eye. Projected to be cat4 over the next day or two.



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146. slavp
Quoting StormW:


Crap.
Not Good!!! LOL It is NEVER good to hear the experts talk like that lol
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145. 606
Hello Bloggers.
I live in St Lucia. We have been mointoring Bill he looks impressive. Thank god this beautiful hurricane missed us. Currently it is very hot and humid, winds are light.There is some wave action along the beach but nothing too serious. Hope we are this lucky for the rest of the season.
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144. 900MB
Quoting IKE:


Look at the water vapor loop I just posted. Trough is not weak...


Plenty of action on that water vapor, many players. Most of them look like they are on the North end, we'll see. I know they say that the trough will push it, but this close, this big, I'll be prepared and take it from there.
Thanks for the WV, Ike!
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Quoting StormW:


Crap.

I concur with your crap.
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Quoting nrtiwlnvragn:


Same basic thinking was in yesterday's TROPICAL DISCUSSION - INTERNATIONAL DESKS

Thanks, nrt.

A segment worthy of sharing out loud:
"ANALYSIS OF THE 200 HPA VELOCITY POTENTIAL ANOMALIES...AS AN INDICATOR OF MJO ACTIVITY...SHOWS A LARGE AREA OF NEGATIVE ANOMALIES OVER THE EASTERN PACIFIC. BOTH THE CLIMATE FORECAST SYSTEM (CFS) AND THE EMPIRICAL WAVE PROPAGATION (EWP) MODELS SHOW THIS AREA SPREADING AND PERSISTING OVER THE CARIBBEAN THROUGH THE END OF AUGUST...WITH A PEAK IN ACTIVITY AROUND THE 23-26 OF THE MONTH. BUT...WHILE THE CFS FAVORS THE CARIBBEAN BASIN FOR MOST OF THE ACTIVITY...THE EWP CONCENTRATES OVER THE TROPICAL ATLANTIC/EAST OF THE ISLAND CHAIN. BOTH MODELS HAVE BEEN HAVING PROBLEMS AS OF LATE IN RESOLVING THE INTENSITY/PERSISTENCE OF THE MJO ACTIVITY...SO WE HAVE SOME RESERVATIONS ON HOW MUCH CONFIDENCE TO PUT ON THIS FORECAST. BUT TAKING INTO ACCOUNT THE CURRENT ANALYSIS... AND PREVIOUS TRENDS...IT IS REASONABLE TO ASSUME THAT THE CONDITIONS SHOULD REMAIN FAVORABLE FOR THE NEXT 07-10 DAYS.

"
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So Floodman can that help developement?
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Quoting srada:


I thought at one time they were thinking that the trough could stall? Is that still the case?


The intense outflow from Bill is forecast by the GFS (and other models) to help enhance the ridging to its northeast as the outflow sinks and dries/warms the air.

Essentially there will be a squeeze play between this stronger riding to the east and north of Bill and the strong trough to the west.

Bill's influence may be to slow the trough down a bit, which won't prevent it from recurving (as the ridging to its east is oriented too North/South)
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Quoting stormsurge39:
Isnt there a 850 voticity (I think thats how you spell it?)that could help post ANA?


To all intents and purposes, the 850mb vorticity IS Ana (in that location). The vorticity is a function of the disturbance and not a separate entity
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What a westward shift on the 12Z GFS. It used to be the eastern outlier, now it's joined the CMC and NOGAPS. Very interesting to see if other runs weaken the trough.

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Interesting video...apparently, though, this trough-breaking was predicted well in advance by NHC and the models.
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134. jpsb
Quoting snotly:


From Canada with love.
lol, from the Alaska whether machine with hast. /JOKE
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Quoting atmoaggie:

I think it may be too early to tell that. Anything more than a week's worth of MJO forecast is one of the most unreliable results from our current operation model suite.

We were encouraged that the MJO had moved on and diminished. Might have been premature.


Definitely keep us posted on that...
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Quoting atmoaggie:
I thought we might be going into a fairly long quiet period in the Atlantic, as did others here (I remember StormW and I agreeing on this almost a week ago).

Well, we might be wrong. MJO was tracking out of our domain and weakening in amplitude. Well, it took a turn back to our domain in the last day and the GFS and the ensemble mean both bring it well back into our domain. And the both model results bring back a bit of the amplitude in the near term and a lot in the long term.

If this verifies, we will very likely have another bout of developing waves possibly just before the forecasted development 7 days from now as per Dr M's post above.

The forecast: (The large dot is the current, the thin red line is the last 20 days, the thick blue is the next 7 days forecast by GFS, the thick green is the next 7 forecasted ensemble mean)



If you can see where the Aug 12,13,14 points fall in this plot, well do you know what was going on then?


Same basic thinking was in yesterday's TROPICAL DISCUSSION - INTERNATIONAL DESKS
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Quoting cheetaking:
Since a debate has been going on about Hurricane Isabel busting through a trough, here is a video of it. Watch what it does around :12 to :16.



Looks like timing will be critical, if the trough is slow then expect an Isabel like result.
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Isnt there a 850 voticity (I think thats how you spell it?)that could help post ANA?
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12z GFS drives Bill right into Canada. Wow.
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128. srada
Quoting breald:


I see it.

One thing about the weather in New England is it can change over night. I remember I went to bed thinking it was going to be sunny the next day, because that is what the weatherman said. And woke up to rain all day. I hope things work out the way they think they will. Sorry Bermuda.


I thought at one time they were thinking that the trough could stall? Is that still the case?
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127. jpsb
Quoting cheetaking:
Since a debate has been going on about Hurricane Isabel busting through a trough, here is a video of it. Watch what it does around :12 to :16.

Wow, I think the argument is over. Very nice.
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Quoting jeffs713:
]
Things against organizing:
No LLC.
No closed circulation at any level (ex-Ana is an open wave).
No organization to speak of.
Marginal upper-level winds. (at least when I checked yesterday)

Things for organizing:
Good SSTs and OHC.
Energy left over from the storm and the soon-to-be nearby front.

Overall.. things aren't looking good for ex-Ana.

Thanks Jeff - I hope it stays that way!
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Quoting TexasHurricane:


Hmmmm...could get interesting... I was thinking we were suppose to have a slower September, but with this that may not be the case??

I think it may be too early to tell that. Anything more than a week's worth of MJO forecast is one of the most unreliable results from our current operation model suite.

We were encouraged that the MJO had moved on and diminished. Might have been premature.
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Quoting jeffs713:

The trough won't have much of an ability to intensify him, as it will speed him up as it turns him (once Bill is parallel to the trough). It will actually serve to weaken him between speeding him up and inducing shear along the axis of the trough, in combination with moving him to lower SSTs.


Just adding to that...

With some tropical cyclones (i.e. IKE) the energy associated with the storm can get absorbed by a mid-latitude baroclinic (fueled by temperature difference) storm and can act to energize both storms.

However, with Bill the trough and Cyclone remain separate with Bill racing north and then northeast ahead of the trough. This should prevent any baroclinic energy from feeding into Bill which would keep it stronger for longer over colder water.
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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.