Bill intensifies to Category 4; globe has 5th warmest July on record
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
Reader Comments
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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.
that is kind of what I was wondering. was there ever a previous storm that the trough did not effect it? was isabel the only one?
But maybe we can not be so stressed....
and the purpose of your post was what?
Hurricane Isabel in 2003 busted through the trough and hit the Carolinas. It's slim, but there is a chance Bill could do that.
Bear in mind that Isabel was an annular storm; annular stiorms are less effected by shear and marginal conditions...I just can't recall whether or not the effects of trof and lows are the same or decreased for annulars
APPEARS THAT THE TROUGH WHICH IS CURRENTLY ERODING THE WESTERN
PORTION OF THE RIDGE WILL WEAKEN AND THE HIGH WILL EXPAND WESTWARD."
This was about 5 days before landfall....
WAlshy - Your picture mataches your avatar. All I see is a red X...
Of course you count! are the waves kicking up yet?
And Squawk - what's with the sarcasm? Seems like a very good observation from Chicklit and a good question that a lot of people on here are knowledgeable enough to answer.
I think it creates high pressure on the 'outside' of the storm as air is sucked into the center and spills over the top. so to speak.
150 with a pressure around 935 would be my guess.
However 160 Category 5 certainly is possible as the SSTs increase.
About 30 minutes ago we had showers with gusty winds that lasted about 5 minutes. Now we have a beautiful sunny day. It went by so quickly!
Even my wunderground has only gotten our weather right about 40% of the time for the past year.
The rain they say we're going to get goes to our West and North, we've barely gotten any of the rain that's predicted, but we've gotten weather that wasn't s'posed to hit us plenty. So... I'm still watching Bill.
it was a question, not a guesser. is that not what this blog is for? to ask questions that you are not sure about.
Guess I missed it, but I did not see a question in there anywhere. Maybe my browser is dropping text, ya think?
Glad it seems it won't be any worse.....
1- Where will that Bermuda high be in 2 days, and will Bill slip under it, or blast it.
2- What is the bias for a major hurricane? Refresh my memory, does it tend to go left or right when it is so strong? With only warmer waters and low shear ahead over next few days, it only looks to get more intense, which is why I ask about the bias. Big storms can make their own weather.
Thanks!
The trough apparently wasn't as strong as this one.
"The landfall forecasts were exceptionally accurate. The track forecast errors verifying at 1800 UTC 18 September (1 h after landfall) had errors of 6, 12, 6, 16, 31, 86, and 118 n mi for the 12, 24, 36, 48, 72, 96, and 120 h forecasts, respectively."
http://www.nhc.noaa.gov/2003isabel.shtml?
Here is the track archive:
http://www.nhc.noaa.gov/archive/2003/ISABEL_graphics.shtml
Yeah I was one of the ones on last night. Happy to see Bill's taken a turn away from us.
The surfers will have a blast over the weekend!
East End of Long Island here and ditto! It has been so long since major storm, and with gypsy moths weakening so many trees over past 7 years, wind is a scary thought, a storm even scarier!
Figure 2. Visible satellite image of Bill's eye zoomed in, taken from NASA's Aqua spacecraft at 12:40pm EDT Tuesday July 18, 2009.
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Let's get some more photo's from this "future seeing" satellite so we know what happens NEXT month.
Though some models (NOGAPS, CMC, and few GFS esnembles) are weakening this trough as well.. So it's all speculation. We'll have to see what this so called "monster trough" will do. I'm still not confident on a sharp recurvature just yet, you can see models spread out at the end of there runs, which makes the NHC 5 day cone.
Yeah me to, at 5 days prior they really were not sure if it was going to hit the OBX and SE VA, but it did. Gave me a whole day to prepare.
A lot is riding on that trough ...
But it does look this a.m. like Bill will take the NW course along the edge of the Antilles for the next day or two. I just hope it keeps going up the ATL the way it's forecast to.....
Yeah it does....there also looks to be 2 other areas of cocern in the Atlantic as well.
You can see the trough in the central USA advancing east...
So I guess the big question is if we really need to be worried about another potentially dangerous hurricane hitting Halifax?
Any thoughts from the experts?
Something I learned with Bertha last year is that the trough actually can push the storm along in front of it, almost like a bulldozer. It's pretty interesting to watch....
The models do show the powerfull effect of Bill on the weather around it. Specifically it's outflow aloft causes additional subsidence and ridging to its north - more that there otherwise would be.
Fortunately, the trough to it's west is quite a bit stronger than a normal mid-August trough and it will definitely recurve the storm. The only tough question remaining is exactly where... It is my opinion that the US will not feel much wind from Bill, but Canada could get a good wallop.
Look at the water vapor loop I just posted. Trough is not weak...
lol.. yeah finally pried my fingers from the keyboard and got some rest. Hoping he maintains his current path as well. Some howling winds outside and hearing some birds going nuts...other than that all appears normal for now. I'll check out the beaches sometime in the next day or so and post pics if I see any nice waves.
That makes feel better! Your right about Wilma, she obeyed. Still gonna be cool getting towed into Bill's 12 foot faces this weekend off Hatteras Light!
IOW, it doesn't take a powerful trough to force an unwilling storm to curve N, it simply takes the absence of a ridge/high to allow it to follow its natural inclination.
Think of a storm as a car with its front wheels badly out of alignment, so that it wants to turn right. But if it's going over terrain that's tilted so that the left side is lower than the right, that natural pull to the right can be partially or compeletly offset and the car may go actually move left, or straight, or at least less right than it would on a flat surface.
But then let a patch of flat territory come up, or territory with the oppsite tilt, and now of course the car is free to turn right as the wheels want to do anyway.
Oops, thanks for the update Dr Masters.
I'm pretty sure he meant August. :-)
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