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 Thundercloud01221991:
Flight Level Winds of 135 knts which translates to 120 knts at the surface if you take 90% of flight level

I heard that is what you do when they are in the eyewall

According to Mark Powell's study detailed in his June 2009 Weather and Forecasting Paper, that can actually range from 0.6 to 1.1, but is heavily populated in the 0.8 direction.

The differences are largely dependent on the stadium effect and the difference between where the flight level wind is measured and the corresponding point at the surface.
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Quoting KarenRei:


Well, duh. As everyone knows, *that* starts with an earthquake...


An earthquake? I thought it was an asteroid impact followed by global thermonuclear war...you know, you miss a few meetings and they re-write the manual on you
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So wind speeds are Cat 3, and minimum central pressure is knocking on the door of Cat 4.

Anyone have a handle on storm surge?

And what ever happened to Total Kinetic Energy? Is the experimental SS scale (in use for 2009) an attempt at capturing that?
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I hope that the Westward shift in the model guidance is just that and not a new trend. How mant times have we seen one nudge left followed by more and more shifts towards the West.
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Quoting KarenRei:


Well, duh. As everyone knows, *that* starts with an earthquake...


lol
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368. WAHA
Quoting yonzabam:
Let's suppose Bill makes it to borderline cat 4/5. How strong do you think it would be by the time it reached Nova Scotia?
If it would make it there, I'd say a cat. 2
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Quoting reedzone:
There maybe a slight change in what the forecast trough might do. The 12Z models have shifted a good clip to the west, but still not enough to cause a USA landfall, which is good :)
Here's my forecast based on the forecast models and pattern steering trends.

Photobucket



AH the good old sqeeze play. HIKE, Bill I want you to go through these two guys and dont look back.
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Let's suppose Bill makes it to borderline cat 4/5. How strong do you think it would be by the time it reached Nova Scotia?
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Afternoon; with the statistical peak of the season around Sept 10th, I'm wondering if we might see another Bill, in terms of intensity, before the season is over or whether this will be the last big one; given his more Northward track north of the Islands, there might be less upwelling effects/warm SST's on a lower track CV storm in the coming weeks but time will tell.
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Here are the last 21-GFS forecast cycles for Bill. GFS has gone significantly left and the track as become more curved, I guess.

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Quoting atmoaggie:

Hey there.
Given that the GFS has convective parameterization, I would think it rather assuming to depend on the convection to determine the 200 hPa results. But, I do not know off hand just how the MJO is derived from the GFS forecast. Could be the 200 hPa, as you say, but then the next question is how much does the convective parameterization impact the 200 hPa?

I am afraid I do not know these answers. Given, though, that GFS initializes off of current obs and some limited historical obs, I doubt that every run includes information about the origin of an MJO pulse.

I do know that the NICAM, a global, cloud-resolving model developed by the Japanese has been very successful in global MJO tracking and genesis. Currently, I don't know of any operational versions of this model available to us. By cloud-resolving, I expect that to mean it has no need for convective parameterization and, thus, handles the points you bring up far better...and is the reason it has been successful.


Thanks for the response!

I guess I'll have to do more reading on NICAM...it's not the first time I've heard about it lately. Would have to have pretty good resolution to be "cloud resolving" and not just parameterizing convection...


I think a better way of phrasing what I was trying to say is...

Divergence aloft (MJO or otherwise) impacts conditions at the surface...enhances convergence and can alter flow.

However, conditions at the surface can also change the flow aloft causing divergence.

Basically, it's just hard to isolate an MJO signal from other influences.


Regardless, the fact that the GFS shows enhanced divergence aloft and convection in the Atlantic Basin/Eastern Pacific extending longer is interesting for the hurricane season...
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360. WAHA
Link to my site. I updated it.
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Quoting juniormeteorologist:
Does anybody think Bill will be an Annular Hurricane like Isabel in 03


Not anymore.
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Quoting scott1968:
The reality of it all is that no matter where Bill goes it will not be the end of the world.


Well, duh. As everyone knows, *that* starts with an earthquake...
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Flight Level Winds of 135 knts which translates to 120 knts at the surface if you take 90% of flight level

I heard that is what you do when they are in the eyewall
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Quoting scott1968:
The reality of it all is that no matter where Bill goes it will not be the end of the world.


That's a really STUPID comment. For some people it may be...
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There maybe a slight change in what the forecast trough might do. The 12Z models have shifted a good clip to the west, but still not enough to cause a USA landfall, which is good :)
Here's my forecast based on the forecast models and pattern steering trends.

Photobucket
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The Hunter just recorded an extrapolated minimum central pressure of 944.3 - Bill's still getting stronger. The vortex messages today have shown a steady downward trend - 952, 950, 949 - and I expect the next one to clock in around 947. This latest pass, through the strong northeastern eyewall, recorded SFMR surface-level winds of 103 kts.

I'm glad to be on dry land.
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352. slavp
Quoting juniormeteorologist:
Does anybody think Bill will be an Annular Hurricane like Isabel in 03
Speaking for myself....No
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Does anybody think Bill will be an Annular Hurricane like Isabel in 03
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The reality of it all is that no matter where Bill goes it will not be the end of the world.
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Hurricane Hunter now found Bill at 944 mb
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Link I'm new here, please be kind..can anyone tell me what is that spin of the coast of north carolina..just curious.

thanks

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Quoting tramp96:
Might want to watch Frank Strait on AccuWeather. He is talking about how the heat from a hurriccane can push a trough around.

http://www.accuweather.com/video-on-demand.asp?video=34605198001&channel=VBLOG_STRAIT&title =Wednesd ay Bill Update


I watch him too...
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Recon found a 944mb pressure.
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342. 7544
last few frames is bill moving slower
Link
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Quoting reedzone:
All models have shifted west, NOGAPS has Maine landfall, near Canada though. Waiting on the BAMM runs to shift west, those are the only 3 runs that sharply recurve Bill east. The rest of them show a slow recurvature.


I agree with the common consensus of the models. Maine, Nova Scotia, and Newfoundland probably are going to receive the most direct impacts from Bill.

By the way, I have a new blog entry:
Today in the Tropics - 8/19/09 - Hurricane Bill
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Quoting OSUWXGUY:
Hey Atmo-

Does the modeled MJO cause the enhanced tropical thunderstorm activity (and cyclones) or do the cyclones themselves cause the signal in the 200hPa divergence???

Especially with the models, you get the chicken or the egg conundrum...

My understanding was that a TRUE MJO pulse emanated from the very strong convection in the Indian Ocean/Indonesia region and "reverberated" around the globe generally moving easterly like a wave.

The signal we seen in the 200hPa anomalies often seem more of a locally enhanced event

Hey there.
Given that the GFS has convective parameterization, I would think it rather assuming to depend on the convection to determine the 200 hPa results. But, I do not know off hand just how the MJO is derived from the GFS forecast. Could be the 200 hPa, as you say, but then the next question is how much does the convective parameterization impact the 200 hPa?

I am afraid I do not know these answers. Given, though, that GFS initializes off of current obs and some limited historical obs, I doubt that every run includes information about the origin of an MJO pulse.

I do know that the NICAM, a global, cloud-resolving model developed by the Japanese has been very successful in global MJO tracking and genesis. Currently, I don't know of any operational versions of this model available to us. By cloud-resolving, I expect that to mean it has no need for convective parameterization and, thus, handles the points you bring up far better...and is the reason it has been successful.
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And to go along with that Karen said yeah sure one ensemble member has shifted westward, but it only takes a few to begin a trend. We'll have to see over the next few model runs if more ensemble members come to an agreement with that. I'd say no as of right now....
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Quoting nrtiwlnvragn:


Canadian Hurricane Centre

Tropical Cyclone Information Statements

We issue information statements when a tropical cyclone is expected to bring tropical-storm force winds (gales 63-117 km/h) into Canadian territory or territorial waters within 72 hours (3 days).


Awsome thanks
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Quoting TampaSpin:
Gettin might close to the Coastline....HUM.


Uh, what is that showing in the GOM at the end of the run?
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Quoting futuremet:


This wishcasting stuff is getting old. Just make sure your forecast is in harmony with the current data. Wen people get too biased to satisfy their outcome--that is wishcasting, regardless if they want a storm to hit them or not.


Hey at least his observation of the information is possible. People are on here talking about something that doesn't even exists going into the GOM or Florida.
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I don't like the end of that tampa (back to lurking)
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@324

Nicely put Karen...
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It looks like the last few images of the satellite loop that the western outflow of Bill may be improving... If so I'm thinking Bill could get to 140-150mph sustained before midnight.
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All models have shifted west, NOGAPS has Maine landfall, near Canada though. Waiting on the BAMM runs to shift west, those are the only 3 runs that sharply recurve Bill east. The rest of them show a slow recurvature.
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Quoting weathersp:


The timing of that trough is going to be critical.. I also see there that Bill is trying to bust through the trough just off Long Island.


I say timing is always everything, Friday is about 35 hours from now on EST, and thats about 630 miles that he will move WNW, if the trough pushes him out to see..

You can never forecast wen a storm will stall, it just happens, and like i said the other day, all storms do some kind of crazy tactic while out in the Ocean, and Bill has yet to do his..

MAybe his will be to miss the trough, or maybe he will stall, or turn in a different direction, thats the thing about Tropical Weather, it is full of surprises and that what makes it so interesting
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This wishcasting stuff is getting old. Just make sure your forecast is in harmony with the current data. Wen people get too biased to satisfy their outcome--that is wishcasting, regardless if they want a storm to hit them or not.

The thing is, there's so much uncertainty in the models that almost any guess that doesn't have Bill going into the Gulf is a possibility. The cone, as wide as it is, only represents a 2/3rds probability. That means, for example, that there's about a 1/6th chance that Bill will strike west of the cone. Not a huge chance, but not particularly comforting, either. To put it another way, look at the GFS ensemble models. In the last run, one of them went straight through Boston.

Is this likely? Not really. Should Boston residents just assume they're safe? No to that either. Anyone on the east coast who (foolishly) didn't do their hurricane preparations earlier ought to take the time to do so now. Get those dead limbs off those trees, restock your emergency supplies, etc.
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.