The future of flooding

By: Dr. Jeff Masters , 10:06 PM GMT on February 19, 2008

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Are storms getting more extreme due to climate change? That is a difficult question to answer, since reliable records are not available at all in many parts of the world, and extend back only a few decades elsewhere. However, we do have a fairly good set of precipitation records for many parts of the globe, and those records show that the heaviest types of rains--those likely to cause flooding--have increased in recent years. According to the United Nations' Intergovernmental Panel on Climate Change (IPCC) 2007 report, "The frequency of heavy precipitation events has increased over most land areas". Indeed, global warming theory has long predicted an increase in heavy precipitation events. As the climate warms, evaporation of moisture from the oceans increases, resulting in more water vapor in the air. According to the 2007 IPCC report, water vapor in the global atmosphere has increased by about 5% over the 20th century, and 4% since 1970. Satellite measurements (Trenberth et al., 2005) have shown a 1.3% per decade increase in water vapor over the global oceans since 1988. Santer et al. (2007) used a climate model to study the relative contribution of natural and human-caused effects on increasing water vapor, and concluded that this increase was "primarily due to human-caused increases in greenhouse gases". This was also the conclusion of Willet et al. (2007).

More water vapor equals more precipitation
This increase in water vapor has very likely led to an increase in global precipitation. For instance, over the U.S., where we have very good precipitation records, annual average precipitation has increased 7% over the past century (Groisman et al., 2004). The same study also found a 14% increase in heavy (top 5%) and 20% increase in very heavy (top 1%) precipitation events over the U.S. in the past century. Kunkel et al. (2003) also found an increase in heavy precipitation events over the U.S. in recent decades, but noted that heavy precipitation events were nearly as frequent at the end of the 19th century and beginning of the 20th century, though the data is not as reliable back then. Thus, there is a large natural variation in extreme precipitation events.

Pollution may contribute to higher precipitation
It is possible that increased pollution is partly responsible for the increase in precipitation and in heavy precipitation events in some parts of the world. According to Bell et al. (2008), summertime rainfall over the Southeast U.S. is more intense on weekdays than on weekends, with Tuesdays having 1.8 times as much rain as Saturdays during the 1998-2005 period analyzed. Air pollution particulate matter also peaks on weekdays and has a weekend minimum, making it likely that pollution is contributing to the observed mid-week rainfall increase. Pollution particles act as "nuclei" around which raindrops condense, increasing precipitation in some storms.

The future of flooding
It is difficult to say if the increase in heavy precipitation events in recent years has led to more flooding, since flooding is critically dependent on how much the landscape has been altered by development, upstream deforestation, and what kind of flood control devices are present. One of the few studies that did attempt to quantify flooding (Milly et al., 2002) found that the incidence of great floods has increased in recent decades. In the past century, the world's 29 largest river basins experienced a total of 21 "100-year floods"--the type of flood one would expect only once per 100 years in a given river basin. Of these 21 floods, 16 occurred in the last half of the century (after 1953). With the IPCC predicting that heavy precipitation events are very likely to continue to increase, it would be no surprise to see flooding worsen globally in the coming decades.

Jeff Masters

References
Bell, T. L., D. Rosenfeld, K.-M. Kim, J.-M. Yoo, M.-I. Lee, and M. Hahnenberger (2008), "Midweek increase in U.S. summer rain and storm heights suggests air pollution invigorates rainstorms," J. Geophys. Res., 113, D02209, doi:10.1029/2007JD008623.

Kunkel, K. E., D. R. Easterling, K. Redmond, and K. Hubbard, 2003, "Temporal variations of extreme precipitation events in the United States: 1895.2000", Geophys. Res. Lett., 30(17), 1900, doi:10.1029/2003GL018052.

Groisman, P.Y., R.W. Knight, T.R. Karl, D.R. Easterling, B. Sun, and J.H. Lawrimore, 2004, "Contemporary Changes of the Hydrological Cycle over the Contiguous United States: Trends Derived from In Situ Observations," J. Hydrometeor., 5, 64.85.

Milly, P.C.D., R.T. Wetherald, K.A. Dunne, and T.L.Delworth, Increasing risk of great floods in a changing climate", Nature 415, 514-517 (31 January 2002) | doi:10.1038/415514a.

Santer, B.D., C. Mears, F. J. Wentz, K. E. Taylor, P. J. Gleckler, T. M. L. Wigley, T. P. Barnett, J. S. Boyle, W. Brüggemann, N. P. Gillett, S. A. Klein, G. A. Meehl, T. Nozawa, D. W. Pierce, P. A. Stott, W. M. Washington, and M. F. Wehner, 2007, "Identification of human-induced changes in atmospheric moisture content", PNAS 2007 104: 15248-15253.

Trapp, R.J., N.S. Diffenbaugh, H.E. Brooks, M.E. Baldwin, E.D. Robinson, and J.S. Pal, 2007, Severe thunderstorm environment frequency during the 21st century caused by anthropogenically enhanced global radiative forcing, PNAS 104 no. 50, 19719-19723, Dec. 11, 2007.

Trenberth, K.E., J. Fasullo, and L. Smith, 2005: "Trends and variability in column-integrated atmospheric water vapor", Climate Dynamics 24, 741-758.

Willett, K.M., N.P. Gillett, P.D. Jones, and P.W. Thorne, 2007, "Attribution of observed surface humidity changes to human influence", Nature 449, 710-712 (11 October 2007) | doi:10.1038/nature06207.




Winter Flooding (Jmroh)
This is the result of extreme snowmelt and 4 inches of rain.
Winter Flooding
Yellow River Starke County Indiana (StarkeHistorian)
Kankakee Game Preserve, 10 Mile Road: The Yellow River crested this morning at 12.14' at the US35 bridge at 11:45AM. This was 2.14' over flood stage. The record is 15.3 Jan 1, 1991.
Yellow River Starke County Indiana

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300. hahaguy
5:29 PM GMT on February 24, 2008
we don't use the "H" word in here until it's time. lol
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299. MrSea
5:27 PM GMT on February 24, 2008
Its almost hurricane season!
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295. hahaguy
5:22 PM GMT on February 24, 2008
life is treating me pretty good jfv.
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294. Patrap
11:20 AM CST on February 24, 2008
UNYSIS 10-day GFSx Link
Member Since: July 3, 2005 Posts: 426 Comments: 128632
292. hahaguy
5:18 PM GMT on February 24, 2008
good day to you also
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290. hahaguy
5:12 PM GMT on February 24, 2008
thank god for this cold front. after the last few days we need a cool down
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287. Weather456
12:06 PM AST on February 24, 2008
the section in italics was just added in
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286. hurricane23
11:36 AM EST on February 24, 2008
Good afternoon!

Really enjoyed this weekend with these really warm temps but unfortunately we'll have to deal with what looks to be a pretty significant cool-down around mid-week.Hopefully this is one of the last ones cause this cold weather is really getting old especially if you have to get up early morning in 40 degress weather.Bring on the summertime temps! Adrian

THUNDERSTORM OUTLOOK: A COLD FRONT IS FORECAST TO MOVE ACROSS
MAINLAND SOUTH FLORIDA TUESDAY NIGHT INTO WEDNESDAY MORNING.
THUNDERSTORMS WILL BE POSSIBLE AS THIS FRONT SWEEPS ACROSS THE
AREA. LOW LEVEL WINDS WILL INCREASE ENOUGH TO ALLOW FOR THE
POSSIBILITY OF GUSTY WINDS TO ACCOMPANY A FEW OF THE STORMS.


TEMPERATURE OUTLOOK: A COLDER AND DRIER AIR MASS WILL SPREAD SOUTH
ACROSS MAINLAND SOUTH FLORIDA ON A NORTHERLY WIND FLOW BEHIND THE
FRONT. ON THURSDAY MORNING, TEMPERATURES IN PORTIONS OF GLADES AND
HENDRY COUNTIES AND NORTHEASTERN COLLIER COUNTY COULD BOTTOM OUT
IN THE MID TO UPPER 30S, WITH WIND CHILLS IN THE LOWER 30S. WIND
CHILLS ACROSS THE EAST COAST METRO AREAS COULD FALL TO AROUND 40
DEGREES.


www.AdriansWeather.com
Member Since: May 14, 2006 Posts: 8 Comments: 13804
285. Weather456
12:05 PM AST on February 24, 2008
....SYNOPSIS....

GULF OF MEXICO/NORTHWEST ATLANTIC OCEAN WEST OF 50W....

The upper level pattern across much of the Gulf region continues to maintain a relatively dry airmass leading to much subsidence, hindering any development of vertical clouds. A combination of weak surface pressure pattern and moisture within the surface layer is leading to scattered to broken stratus and fog across the area from the Mexican Gulf Coastal Plain, the Gulf of Mexico west of 90W and north of 25N from Coastal Texas/Louisiana to the Florida Peninsula. In addition to that, a rope cloud is seen pushing across the Northwest Gulf from the Texas/Mexican Border to just south of the Mississippi Delta. This feature is identified as a cold front due to the change in wind direction reported by synoptic stations. The surface pressure pattern is also allowing fair skies to dominate the area with winds and seas remaining exceptionally light today with light variable winds below 10 knots and seas of 2-3 ft across the entire Gulf waters. Meanwhile, a second cold front goes from 26N/89W across Florida near Lake Okeechobee. Most of moisture along this feature is in the form if mid-upper level cloudiness driven by southwesterly upper winds.

A relatively weak cold front is pushing across the Atlantic from South Florida to beyond 34N/60W. Showers are possible in clusters of shallow to moderate clouds along the frontal boundary west of 75W. Very weak surface pressure pattern exist ahead of the front allowing fair weather and very light winds over the area.

CENTRAL AMERICA AND THE CARIBBEAN REGION....

Upper ridging and very dry stable flow covers most of the Caribbean Basin this morning thereby hindering any shower activity and allowing fair conditions to exist at the surface. High pressure ridging remains in control providing 10-25 knot easterly flow, which is driving 6-10 ft swells through the region. This easterly flow will bring clusters shallow cloudiness with possible showers to the Lesser Antilles and along the Central America Isthmus further downstream.

TROPICAL ATLANTIC SOUTH OF 20N WEST OF 40W....

An upper trough axis roughly lies from 40N/30W to the island of Saint Lucia near 13N/61W. Very dry confluent stable flow is seen from the Islands to 45W with a pronounce flow of mid-upper cloudiness and possible showers seen from the ITCZ near 10N/50W to beyond 20N/30W. The surface Azores High is analyzed 1028 mb at 33N/30W. This high is producing a large area of moderate to strong trades, 6-10 ft northeast swells and fair weather across the Atlantic with only scattered dry air stratocumulus embedded within this flow.

by W456
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284. Weather456
10:13 AM AST on February 24, 2008
....SYNOPSIS....

GULF OF MEXICO....

The upper level pattern across much of the Gulf region continues to maintain a relatively dry airmass leading to much subsidence, hindering any development of vertical clouds. A combination of weak surface pressure pattern and moisture within the surface layer is leading to scattered to broken stratus and fog across the area from the Mexican Gulf Coastal Plain, the Gulf of Mexico west of 90W and north of 25N from Coastal Texas/Louisiana to the Florida Peninsula. The surface pressure pattern is also allowing fair skies to dominate the area with winds and seas remaining exceptionally light today with light variable winds below 10 knots and seas of 2-3 ft across the entire Gulf waters. Meanwhile, a cold front goes from 26N/89W across Florida near Lake Okeechobee. Most of moisture along this feature is in the form if mid-upper level cloudiness driven by southwesterly upper winds.

by W456
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283. davidw221
10:40 AM GMT on February 24, 2008
Hey Seflagamma, better get your winter clothes out, Thursday the LOW with be 50, and thats cold for your part of the world!
P.S. enjoy the warm temps now.
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282. hydrus
11:08 PM GMT on February 23, 2008
PATRAP-Thanks again,just finished the google search on Charley & Jeanne.I survived both of them.
Member Since: September 27, 2007 Posts: 1 Comments: 21409
281. Patrap
4:37 PM CST on February 23, 2008
1980..Yup,went to Boot Camp in July 80, Carter was still President.
Anything past "77" though,
getting a lil fuzzzy now . LOL!!!
Member Since: July 3, 2005 Posts: 426 Comments: 128632
280. hydrus
10:29 PM GMT on February 23, 2008
PATRAP-I started on a Tandy(Radio Shack) 64K in 1980.You probrably rememeber that one.
Member Since: September 27, 2007 Posts: 1 Comments: 21409
279. Patrap
4:27 PM CST on February 23, 2008
Thats okay, I started with webtv a few years back
Member Since: July 3, 2005 Posts: 426 Comments: 128632
278. hydrus
10:17 PM GMT on February 23, 2008
V26R AND PATRAP-Thank you for responding to my post.I have been studying weather for a long time,but I am a beginner on the computer & sometimes have trouble finding the information I need.computers sure have changed over the years.
Member Since: September 27, 2007 Posts: 1 Comments: 21409
277. Patrap
4:00 PM CST on February 23, 2008
Okay...V26R ,I modified it a lil,the pic..LOL
Member Since: July 3, 2005 Posts: 426 Comments: 128632
276. V26R
9:56 PM GMT on February 23, 2008
That works for me also Hydrus
Google has a large archive of images
available
Member Since: July 20, 2006 Posts: 0 Comments: 1762
275. V26R
9:55 PM GMT on February 23, 2008
Pat
Browser is Fine, Just a massive Pix
And I hope they did get your message!
Member Since: July 20, 2006 Posts: 0 Comments: 1762
274. Patrap
3:52 PM CST on February 23, 2008
Hydrus One can use the hurricane archive on the Tropical Page of wunderground for radar landfall loops. But for Specific storm Sat Pix,.. just Google the Storm Name and year in Google images. Thats what I usually do.
Member Since: July 3, 2005 Posts: 426 Comments: 128632
273. Patrap
3:48 PM CST on February 23, 2008
V26R, the Pic is fine on FireFox.
Must be ya browser.

Its a Big message anyway.
Member Since: July 3, 2005 Posts: 426 Comments: 128632
272. Weather456
5:33 PM AST on February 23, 2008
March 4 Primaries
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271. hydrus
9:30 PM GMT on February 23, 2008
PATRAP-Is there a web sight to retrieve sattelite photos of the hurricanes listed in storm history archives?
Member Since: September 27, 2007 Posts: 1 Comments: 21409
270. V26R
9:25 PM GMT on February 23, 2008
Hey Pat, think you could have made that Pix any bigger?
Member Since: July 20, 2006 Posts: 0 Comments: 1762
269. surfmom
8:35 PM GMT on February 23, 2008
Thankfully, being on the blog I saw the hot coming in for this weekend, so all we had all the trailer topped out with water in the tanks so we could hose the horses down. They do not do well with this constant switching from a brief cold front to heat. They tighten up when they get quick cold flashes and we have to work much harder to avoid injuries.
Member Since: July 18, 2007 Posts: 30 Comments: 26536
268. surfmom
8:29 PM GMT on February 23, 2008
3:30PM Rain just hit SRQ. Thanks to WU had perfect timing today, horses got worked out, and the polo match ended just before the rain appeared.

Very HOT here in SRQ and the Gulf is running the warmest it has since I have been surfing. Last year it went down to 50 and hung out there...I do not think it managed to get below 56 degrees this winter, will go back later and check. The Gomex by the SRQ/Tampa area is already 68 degrees!!!!
Member Since: July 18, 2007 Posts: 30 Comments: 26536
267. 0741
8:04 PM GMT on February 23, 2008
wow it feel like spring have taking over with temp in 90s my ac running like crazy
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265. Patrap
1:40 PM CST on February 23, 2008
But I see the warmth and Humidity is summer-like in your neck of the woods.
Member Since: July 3, 2005 Posts: 426 Comments: 128632
264. Patrap
1:39 PM CST on February 23, 2008
Not here..we behind the front..But Thurs and Fri with 7 inch rain totals sure did. Was bumpy.
Member Since: July 3, 2005 Posts: 426 Comments: 128632
262. Patrap
1:31 PM CST on February 23, 2008
Take a day like today and Think of what you'd have to do if a Hurricane Warning was issued today. Even if you just jot down some plans and crunch some numbers and evac routes. Include the whole family and make it fun too.


Member Since: July 3, 2005 Posts: 426 Comments: 128632
260. hydrus
7:16 PM GMT on February 23, 2008
SEFLAGAMMA-With these lengthy warm spells and short cold snaps,do you think the gulf of mexico will warmer than usual by the time hrricane season arrives?
Member Since: September 27, 2007 Posts: 1 Comments: 21409
259. hurricane23
2:15 PM EST on February 23, 2008
89 degress at MIA.
Member Since: May 14, 2006 Posts: 8 Comments: 13804
258. seflagamma
2:07 PM EST on February 23, 2008
that was for zip 33331 but checked Ft Lauderdale and my area 33321 and it is only 86 degrees... I guess because Weston is further West near the Everglades... but it is HOT outside right now here in Weston.
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257. seflagamma
2:06 PM EST on February 23, 2008
at 2:06pm, in Weston, FL (Broward County just west of Ft. Lauderdale)

91.6 °F / 33.1 °C
Partly Cloudy
Humidity: 41%
Dew Point: 65 °F / 18 °C
Wind: 5.8 mph / 9.3 km/h / 2.6 m/s from the SW
Wind Gust: 5.8 mph / 9.3 km/h
Pressure: 30.03 in / 1016.8 hPa (Falling)
Heat Index: 94 °F / 34 °C
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256. seflagamma
2:03 PM EST on February 23, 2008
Hi everyone, sorry for the confusion this morning and Thanks Shen for the posts of course it was ok to post it.LOL

We broke records all over my area today in SE Florida.

just checked while ago and it was 92 degrees already...
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255. Weather456
2:16 PM AST on February 23, 2008
Using Remote Sensing Tools To Analyze A Cold Front

QuikSCAT - cold front plotted along the axis of changes in wind speed and wind direction. Usually, northerly, northwesterly or westerly winds behind the front and southerly or southeasterly ahead of the front. There is also a pronounce return flow ahead the frontal boundary where the associated upper trough causes the surface high to migrate from west to east.

Satellite Imagery (Visible) - frontal rope structures caused by differential advection. In addition, you can look at the different cloud structures and features. Deep clouds along the front and rapid dissipation of clouds behind the front due to dry air advection.

Total Precipitable Water (TPW) - an excellent tool. The difference between this and water vapor imagery is that TPW measures water content mainly in the lower atmosphere whereas water vapor measures water content within the mid-upper levels. Thus, TPW is better at identifying surface features (I use it to track tropical waves as well). Low TPW values behind the front while high precipitable values along the front.

Time Lags So Extrapolate

During the time of the analysis, the data used maybe taken at different times, which can lead to differences in position by a couple hundred nautical miles. For example, the below satellite imagery is taken at 1415 UTC while the QuikSCAT pass was at 1156 UTC. A simple solution is to extrapolate the QuikSCAT position and this will help position the front where it was difficult or impossible in satellite imagery.

Just A Few

These are just three of several remote sensing tools. They include model derived data (Numerical Models) and satellite soundings.

Hurricane Season 08

These tools will be more than helpful in tracking tropical waves and storms across West Africa, the Tropical Atlantic and Caribbean, where there are few surface synoptic reports, aircraft observations and radiosonde data available.





Image Source: CIMSS


by W456

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254. FLWeatherFreak91
1:24 PM EST on February 23, 2008
It looks like Fl is likely to get some well below normal temps mid-week. In the past 3 days the forecast for next wed night's low has gone from 48 to 37 for odessa. And this cold weather is to be proceeded by a very strong front in Tues. night.
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253. hurricane23
1:21 PM EST on February 23, 2008
87-88 degress across miami at 1:30!Could we hit 90?Probably not.Cool change coming mid-week possibly for the last time thankgod.
Member Since: May 14, 2006 Posts: 8 Comments: 13804
252. Weather456
1:59 PM AST on February 23, 2008
i dont get these preseason forecasts. What good are these forecasts if conditions keep changing from June 1 to September 10. La Nina could move into nuetral (which is bad) or it could stay strong. We just dont kno. I predict that tropical storms will form this hurricane season....lol...the most accurate forecast around.
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251. Patrap
11:25 AM CST on February 23, 2008
Thats a good link for a home page 23. Many will benefit from that site.
Member Since: July 3, 2005 Posts: 426 Comments: 128632

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About

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