New England flooding, air pollution, and the season's first typhoon

By: Dr. Jeff Masters , 2:05 PM GMT on May 15, 2006

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Major flooding has hit southern New Hampshire, southwest Maine, and northeast Massachussetts today, where more than 10 inches of rain has fallen in the past four days. The culprit is a "cut off low", a large low pressure system over the Great Lakes that got separated from the jet stream on Thursday, and has stayed almost stationary since since then, with no upper level winds to push it along. The counter-clockwise flow of air around the low has drawn copious amounts of moist oceanic air over New England. The rains from this moisture have brought the Warner river at Davisville and the Smith River at Bristol to flood stage this morning. With another 1-2 inches of rain expected across the region today, these rivers should crest several feet above flood stage, with moderate to major flooding. The cut-off low is expected to drift slowly northeastward today and get re-absorbed by the jet stream on Tuesday, which will finally bring an end to the worst of the rains. Howver, the weather pattern over the next week is expected to remain wet over the eastern half of the U.S., and more rain is expected in the Northeast later this week as the jet stream continues to remain in a typical Springtime active pattern.


Figure 1. Rainfall amounts for New England estimated by radar, ending at 8:30am EDT Monday May 15.

Air pollution season is here
May marks the beginning of air pollution season in the U.S., when summertime brings the hot temperatures, high amounts of UV radiation, and stagnant air that can trigger air pollution "Action Days". This week marks the annual observance of Air Pollution Awareness week, and at EPA's request, I will be writing several blogs highlighting air pollution. In particular, I'll discuss why one of NOAA's P-3 hurricane hunter airplanes will be in Texas for air pollution research this hurricane season, instead of flying hurricanes.

Quick intro on air pollution
Today, I'll present a quick summary of what pollutants we're concerned about. The Environmental Protection Agency (EPA) calculates the Air Quality Index (AQI) for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide, and nitrogen dioxide. Ozone and particle pollution are the two most serious pollutants in the U.S. Particle pollution alone has been estimated to cause over 20,000 premature deaths the U.S. each year, and 800,000 worldwide (although the exact mortality numbers and definition of "premature deaths" is controversial).

Ozone is a colorless gas composed of three atoms of oxygen. Ozone forms both in the Earth's upper atmosphere and at the surface. Where ozone forms determines whether it is helpful or harmful to your health.

Good ozone naturally forms in the stratosphere, a layer of air about 10 - 30 miles (16 - 48 km) above Earth's
surface. This protective layer shields us from the sun's harmful ultraviolet rays. Without this layer, we would all be blinded and sunburned. Unfortunately, human-created chemicals are destroying this beneficial layer of ozone. Over the South Pole in springtime, the ozone loss is so severe that an "Ozone Hole" forms, letting significant amounts of harmful ultraviolet light reach the surface.

Ozone from the stratosphere sometimes gets transported to the surface, particularly in high mountainous regions. Hikers on Mt. Everest who don't use bottled oxygen can be at risk of death from breathing poisonous levels of ozone near the mountain's summit in some weather conditions.

Bad ozone forms near Earth's surface when the ultraviolet light in sunlight triggers a chemical reaction with "precursor pollutants" emitted by cars, power plants, and industrial sources. These precursor pollutants consist of nitrogen oxides (NOx) and volatile organic hydrocarbons (VOC). Ozone near ground level is a harmful pollutant. Ozone pollution isn't limited to big cities like Los Angeles, Houston and New York. It's also found in smaller cities like Raleigh, NC and Cincinnati, OH. It can be a problem in rural areas, including some national parks. Ozone and the pollutants that react to form it (NOx and VOCs) can also be carried on the wind to affect air quality in urban and rural areas hundreds of miles away.

Particle pollution is a mixture of microscopic solids and liquid droplets suspended in air. This pollution, also known as particulate matter, is made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals, soil or dust particles, and allergens (such as fragments of pollen or mold spores). Unlike summertime ozone, particle pollution can occur year-round. It is worst in summer, though, when winds are lighter and the air becomes more stagnant.

Particles come in a wide range of sizes. Fine particles are less than 2.5 micrometers in diameter. How small is that? About 1/30th the diameter of the average human hair--so small, you'd need an electron microscope to see them.

Some fine particles can be emitted directly (think of smoke from a woodstove). But most are formed secondarily from complex atmospheric reactions of gases such as NOx and sulfur dioxide (SO2), that are emitted from power plants, industries, cars, buses and trucks. These fine particles are the worst for your health, since their small size allows then to penetrate deep into your lungs.

Inhalable coarse particles are larger than 2.5 and up to 10 micrometers in diameter. Sources of coarse particles include crushing or grinding operations and dust stirred up by vehicles traveling on roads. These particles are not as injurious to your health, as their large size allows them to be filtered out more readily by your nose before they reach your lungs.

Typhoon Chanchu
The season's first typhoon, a Category 4 storm with 140 mph winds named Chanchu, has turned north, and is now threatening to strike Hong Hong on Wednesday. Chanchu briefly made it to supertyphoon status on Sunday, when it had 150 mph sustained winds and a 910 mb central pressure. This was good enough for a Category 4 rating on the U.S. Saffir-Simpson scale, but not Category 5--which starts at 156 mph. A supertyphoon is defined as any tropical cyclone in the Western Pacific that attains maximum sustained winds of 150 mph. It is not unusual to get a supertyphoon in May, and this last happened in 2004, when Supertyphoon Nida reached Category 5 status with sustained winds of 160 mph. I'll have more on Typhoon Chanchu tomorrow.


Figure 2. Typhoon Chanchu at peak intensity Sunday, with 150 mph sustained winds and a 910 mb pressure.

Jeff Masters

Spicket River Rises (sabre1100)
Prime water front property for sale...at a barbain price no doubt
Spicket River Rises
York Beach flooding (SkyLazaria)
Mothers Day flooding in York Beach, Maine.
York Beach flooding

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79. Levi32
9:01 AM AKDT on May 15, 2006
Look below 10n around 53w in this image Colby:

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78. Alec
12:59 PM EDT on May 15, 2006
I meant Wilma intensified in a bunch of shear when it moved off the Yucatan Colby....sorry i wasn't specific enough...
77. rwdobson
4:59 PM GMT on May 15, 2006
he'll be ashamed when, in 24 hours, neither of the two pieces have become tropical. i think there's too much SW flow aloft to develop anything for now.
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76. Alec
12:57 PM EDT on May 15, 2006
Posted By: franck at 4:50 PM GMT on May 15, 2006.
Levi..the post wasn't clear. I meant to say that even the area splitting off may take on tropical characteristics as well, not just the convection heading into the Caribbean. I may be too ashamed to post anything here for the next few weeks.

Cheer up:) Weather is an inexact science and even the NHC doesnt understand hurricanes the way they like to(even though they're the real experts, they still get things wrong all the time!)
75. ForecasterColby
4:58 PM GMT on May 15, 2006
Not there wasn't, Alec, at least not when she megabombed.

What wave are you all looking at? The only thing in the atlantic that looks remotely like a tropical wave to me is just off Africa.
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74. Levi32
8:55 AM AKDT on May 15, 2006
Franck I am not sure I understand. Why would you be ashamed?
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73. Alec
12:52 PM EDT on May 15, 2006
If my memory serves me correct, there was 25-30 knots of shear over Wilma when it intensified....
72. franck
4:50 PM GMT on May 15, 2006
Levi..the post wasn't clear. I meant to say that even the area splitting off may take on tropical characteristics as well, not just the convection heading into the Caribbean. I may be too ashamed to post anything here for the next few weeks.
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71. Alec
12:49 PM EDT on May 15, 2006
Levi, it's the unusually strong cold front that came through along with northerly winds from that huge low over the Great Lakes that has helped cool the Gulf a bit....but still looks to be above normal(when last yr most of te Gulf was below normal)...
70. Levi32
8:48 AM AKDT on May 15, 2006
Franck that is quite a surprising statement! I don't know. The shear is just so strong. There is a good ridge over it and there are beginnings of outflow to the north of the convection. It is amazing the convection is holding together considering the conditions.
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69. Levi32
8:45 AM AKDT on May 15, 2006
Yes I see that, and look at how much cooler the waters near the Texas and Louisiana coasts got. Those land temps sure work quick.

Our Atlantic wave looks pretty good right now. Convection has survived overnight and that little spin thing is right under it. I wonder what will happen when the wave interacts with all the heat coming off South America from afternoon thunderstorms?
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68. franck
4:40 PM GMT on May 15, 2006
Even under less than ideal conditions, and in spite of entering into even less ideal conditions, the area of convection in the western Gulf appears to be showing signs of counterclockwise flow, and even banding. I'm throwing out everything I said in the last few posts. Tropical storm in the Gulf in 24 hours, or less. More than likely it will be the area split off and heading toward the Caribbean, or it may even be the split off area.
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67. Alec
12:42 PM EDT on May 15, 2006
If you compare May 12 with May 15 you will see the loop current has weakened just a tad...
66. Levi32
8:40 AM AKDT on May 15, 2006
Yes Alec I think so too. It is amazing how much the land temps over the southern US are affecting the gulf SSTs.
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65. Levi32
8:37 AM AKDT on May 15, 2006
If you want something that is not strictly satellite estimates, then this site is really nice. Just click on the area you want from the pictures around the edge of the global image. It even has SST anomalies for small areas like the gulf.
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64. Alec
12:35 PM EDT on May 15, 2006
Well, as soon as the winter jet retreats and the flow becomes more zonal summer will be here and the SSTs will really start warming up. I've observed the SSTs in the Gulf have actually dropped a little bit due to our cooler than normal nights...
63. StormJunkie
4:30 PM GMT on May 15, 2006
So are the shear levels expected to drop off over most of the Carib and the Gulf in around 10 days or so and is this when we will be expecting the low that was over the Great Lakes will exit the country?
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62. Levi32
8:36 AM AKDT on May 15, 2006
If you want to get really accurate there is a 7-day collabaration of satellite passes.
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61. Levi32
8:34 AM AKDT on May 15, 2006
The SST map I posted is a 3-day collabaration of all the satellite passes over the gulf. That can add up to over 2-3 dozen passes. That is quite accurate. Also they have a reliable meathod of removing a few of the pixels that are covered in clouds.
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60. Levi32
8:32 AM AKDT on May 15, 2006
Alec, yes I think so. This is supposed to be the last major trough in the southeast before the pattern change. The trough will be hanging out in the eastern part of the country all summer but not that far south I think.
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59. Alec
12:31 PM EDT on May 15, 2006
lol You got me Levi.....lol But do you think the one you posted wont be as accurate if there's heavy convection in the Gulf?
58. franck
4:26 PM GMT on May 15, 2006
Levi..possibly..the area which will move across Florida may be affected by that monstrous cutoff low in the northeast, and just be dragged across the Florida peninsula. If the cutoff low subsides, the area may be more likely to take on its own characteristics.
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57. Alec
12:29 PM EDT on May 15, 2006
Levi, do you believe we are at our last cool down for the SE till fall? The long range has us pretty warm again by the weekend...
56. Levi32
8:28 AM AKDT on May 15, 2006
Why!?!?! lol. The one I posted is better and high resolution lol! Also it is from satellite which is better. Yours is so blury I can't read it lol!
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55. Levi32
8:26 AM AKDT on May 15, 2006
The half moving toward Florida will be primarily cold core, so development is not likely especially with all the shear.

Note the GFS has almost all of the Caribbean and the Gulf of Mexico under less than 10-15 knots of shear in 10 days. Joe Bastardi in his Accuweather post this morning said this:

"month ends with trof near west coast, flattening anr retreating northeast off east coast and split piece backing southwest through gulf under ballooning ridge. Gulf opens for business after May 25 though that doesnt mean we have to have development... yet."
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54. Alec
12:25 PM EDT on May 15, 2006
LOL!!!Levi.....I was just looking at that EXACT map a second ago and decided to post the one I did!
53. Levi32
8:25 AM AKDT on May 15, 2006
Franck, one half will move towards Florida, and the other will move over the Yucatan and eventually into the western Caribbean where conditions for development are much more favorable, though I am not suggesting any yet.
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52. Levi32
8:23 AM AKDT on May 15, 2006
Alec I can do better than that lol. Just teasing.

SST map for Gulf
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51. TomP
4:01 PM GMT on May 15, 2006
It's worth pointing out that ozone pollution has been dropping pretty dramatically and steadily in this country for the last three decades.

http://tinyurl.com/nuy6a

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50. franck
4:18 PM GMT on May 15, 2006
Yes, take a look at the jet stream map. The entire area of convection got pushed off the mainland very fast. Now, at least part of the system wants to get picked up and taken eastward. If it drifts into the east central Gulf, the waters are quite a bit warmer there.
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49. Alec
12:22 PM EDT on May 15, 2006
47. IKE
4:14 PM GMT on May 15, 2006
The GFS has been forecasting a low to move across southern Florida Tuesday/Wednesday for the last 3 or 4 days.
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46. Levi32
8:17 AM AKDT on May 15, 2006
Yes Micheal it might be splitting. The low is positioned under the southern half.
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45. Levi32
8:15 AM AKDT on May 15, 2006
Yeah Alec tell me about it. If there was low shear and the SSTs were even the way they are now I would be very scared. That thing looks vicious lol.
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43. Alec
12:13 PM EDT on May 15, 2006
If the Gulf was like 88 degrees and low shear, Id be scared......this thing may be close enough to having one of the characterstics of a deppression(heavy rains)...exactly what Central and S FL needs!
42. Levi32
8:12 AM AKDT on May 15, 2006
It would be interesting if the GFS is right and moves that convection into the Yucatan Peninsula. That tail end of the cold front would eventually make it into the western Caribbean. If some convection were to be touched off when the shear lowers....

Just speculation.
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41. franck
4:08 PM GMT on May 15, 2006
Yes, it looks like Florida will get some rain, but it may also get some wind. Looks like part of the system will break off and get moved eastward with considerable velocity. By the time it gets to the Florida peninsula it may have some cyclonic characteristics, though it may not be a classified system.
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40. Alec
12:08 PM EDT on May 15, 2006
right levi..lol GFS: 1 for 10!!!woohoo!!!
39. Levi32
8:06 AM AKDT on May 15, 2006
You're telling me that there is actually a warm core low under that blob? Wow! Doesn't seem that convection should survive that well under 40 knots of shear.
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38. Alec
12:04 PM EDT on May 15, 2006
WEST CENTRAL AND SOUTHWEST FLORIDA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
900 AM EDT MON MAY 15 2006

.DISCUSSION...THE COLD FRONT IS CURRENTLY ACROSS SOUTHERN GA AND
THE EASTERN FL PANHANDLE WITH SHOWERS AND A FEW TSTMS ALONG THE
LINE. AN AREA OF SHOWERS IS ALSO MOVING ACROSS THE SOUTHERN
GULF...THE LEADING EDGE OF WHICH IS ABOUT TO ENTER THE CENTRAL AND
SOUTHERN OFFSHORE COASTAL WATERS...WITH UPPER LEVEL ENERGY
CURRENTLY OVER MEXICO AND THE WESTERN GULF. DESPITE A DRY SOUNDING
WITH ONLY 0.70" PWATS...THE FRONT TO THE NORTH AND THE SHORTWAVE
TO THE SW WILL QUICKLY MOISTEN THE ATMOSPHERE THIS MORNING. THEN
AS THE FRONT SETTLES INTO THE NORTHERN ZONES AND THE SHORTWAVE
SHIFTS EAST TO OVER SOUTHERN FL AND ENHANCES SEABREEZE
INTERACTIONS...SHOWERS AND THUNDERSTORMS WILL DEVELOP THROUGH THE
AFTERNOON AND INTO THE EVENING. CURRENT FORECAST LOOKS ON TRACK
AND WILL NOT NEED A MORNING UPDATE.
37. Levi32
8:05 AM AKDT on May 15, 2006
Remember the GFS was forecasting some low to develop off this front and move into Florida? This must be it. That also means the GFS actually got something right for a change.
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35. Levi32
8:03 AM AKDT on May 15, 2006
Gulf Sat Loop
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34. Alec
12:02 PM EDT on May 15, 2006
yes, central and S FL will get rain by tomorrow...hopefully will loosen the fire danger
33. RL3AO
4:02 PM GMT on May 15, 2006
It's has some pretty impressive convection though.
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32. Levi32
8:00 AM AKDT on May 15, 2006
Yes Alec, that could mean more convective action in the western Caribbean.

Wow that looks cool in the gulf weather456. That isn't a tropical wave though. Also there is more than 40 knots of shear above that thing. Looks realy neat though. I would be scared out of my socks if there was low shear in that area lol.
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31. RL3AO
4:01 PM GMT on May 15, 2006
Hopefully it can bring some rain to Florida, but I don't know what direction it's heading.
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30. Alec
12:01 PM EDT on May 15, 2006
I believe its a heavy complex of thunderstorms that have come off Mexico and Texas from last night..

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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.