U.S. vulnerability to sea level rise
In the last century, sea level rose 5 - 6 inches (13 - 15 cm) more than the global average of 7 inches (18 cm) along the U.S. Mid-Atlantic and Gulf Coasts, because coastal lands there are sinking. Over 50% of the U.S. coastline is vulnerable or highly vulnerable to sea level rise, according to the Coastal Vulnerability Index (CVI) developed by the United States Geological Survey (USGS). In the U.S., relative sea level rise (the combined effects of global sea level rise plus the fact the land is sinking) is highest along the Mississippi River Delta in Louisiana, where relative sea level rises of 3.2 ft (.98 meters) have been observed during the 20th century. This is one of the highest relative sea level rises in the world. According to the NOAA Tides and Currents sea level rise interactive tool, the U.S. tide gauges that have shown the highest rates of sea level rise over the past century are at Grand Island, LA (1.8 ft rise since 1947), Galveston, TX (1.1 ft since 1957), and Chesapeake Bay, VA (0.6 feet since 1975). Alaska and some areas along the Pacific Northwest coast are at low risk of sea level rise, because the relative sea level is actually falling at present. Land in these regions is rising as it recovers from removal of the weight of the great ice sheets that covered much of North America during the last Ice Age. For example, relative sea level at Kodiak Island, Alaska has fallen by 1.1 feet since 1975, despite the fact global sea level has been increasing.
Figure 1. Twentieth century annual relative sea-level rise rates in mm/year along the U.S. coast. The higher rates for Louisiana (9.85 millimeters [mm] per year, about 3.3 ft/century) and the mid-Atlantic region (1.75 to 4.42 mm per year, 0.6 - 1.4 ft/century) are due to land subsidence. Sea level is stable or dropping relative to the land in the Pacific Northwest, as indicated by the negative values, where the land is tectonically active or rebounding upward in response to the melting of ice sheets since the last Ice Age. Image credit: Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region (data from Zervas, 2001).
U.S. Coastal Vulnerability
The Coastal Vulnerability Index (CVI) takes into account six factors:
1) The geology of the coast. Barrier islands, river deltas, and marshes are the most vulnerable to erosion and sea level rise, while steep, rocky cliff shores are the least. Sheltered bays like Galveston Bay and Tampa Bay are less vulnerable than the exposed coasts. (Note, however, that hurricane storm surges are typically higher in sheltered bays, at least for slow-moving storms).
2) How steep the land near the coast is. Gently sloping lands are the most vulnerable. In the Gulf Coast region, the slope variable has the highest risk ranking along the Louisiana coast, the Texas coast north of Corpus Christi, and the southwest Florida coast.
3) The local rate of sea level rise. The sea level is rising faster along the western Gulf of Mexico than the eastern Gulf. The highest rates of sea-level rise in the Gulf of Mexico (and in the United States) are in the Mississippi delta region (10 mm/yr, or 1 inch/2.5 years).
4) The amount of shoreline erosion going on. Most of the U.S. coast is moderately or severely eroding, and very few areas are gaining (Figure 2).
5) The mean tidal range. Shores that have a large difference between low and high tide are less likely to get a significant storm tide--the height above mean sea level of the sum of the storm surge plus the tide. For example, in a region like Maine, which has a 12 ft range between low and high tide, a storm having a 9 ft storm surge will have a storm tide below local high tide for a quarter of a tidal cycle. Shores with a very narrow tidal range (e.g., the 2 ft tidal range common along the Texas and Louisiana Gulf Coast) will get a storm tide of 8 - 10 feet with the 9 ft storm surge in the above example. Shorelines with a narrow tidal range always get high storm tides regardless of when the storm surge hits.
6) How high the waves at shore are. Obviously, shores that experience higher wave heights are at greater risk. In the Gulf of Mexico, wave energy is highest along sections of the Texas coast and on the southern tip of the Mississippi delta.
Figure 2. Shoreline change around the United States based on surveys over the past century. All 30 coastal states are experiencing overall erosion due to natural processes (e.g., storms, sea-level rise) and human activity. If the shoreline is uncolored, no data was available. Image credit: USGS, 1985, and taken from Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region).
The Coastal Vulnerability Index (CVI) web page gives detailed maps of each section of the U.S. coast, along with specific reasons why each portion of the coast was assigned the ranking it got. A brief summary:
The Gulf Coast
The Gulf Coast has 55% of its length in the "very high" or "high" vulnerability range. Fully 41% of the coast falls in the "very high" range, far more than the 28% in that category along the Pacific coast and 23% along the Atlantic coast. The region around New Orleans is the most vulnerable region of the entire U.S. coast. The Florida Panhandle, as well as the West Florida coast, are at low to moderate risk because the land is not sinking much, wave heights are lower, and the slope of the land is relatively steep near the coast. The Texas coast is considered to be at a high to very high risk because of the relatively high mean wave height, sinking land, and shallow coastal slope.
The East Coast
The East Coast has 50% of its length in the "very high" or "high" vulnerability range. The highest vulnerability areas are typically high-energy coastlines where the regional coastal slope is low and where the major landform type is a barrier island. A significant exception to this is found in the lower Chesapeake Bay. Here, the low coastal slope, vulnerable landform type (salt marsh) and high rate of relative sea-level rise combine for a high CVI value. The coastline of northern New England, particularly Maine, shows a relatively low vulnerability to future sea-level rise. This is primarily due to the steep coastal slopes and rocky shoreline characteristic of the region, as well as the large tidal range.
The Pacific Coast
The Pacific Coast has 50% of its length in the "very high" or "high" vulnerability range. Areas of very high vulnerability include the San Francisco - Monterey Bay coast and in southern California from San Luis Obispo to San Diego, where the coast is most highly populated. The highest vulnerability areas are typically lower-lying beach areas. The low risk, least vulnerable areas generally occur at rocky headlands along cliffed coasts where the coastal slope is steep, relative sea-level is falling, tide range is large, and wave energy is lower. Examples of these areas are the northern coast of Washington, Monterey, and Cape Mendocino, California.
Figure 3. The Coast Vulnerability Index (CVI) for the U.S.
References
Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region.
National Assessment of Coastal Vulnerability to Sea-Level Rise: Preliminary Results for the U.S. Gulf of Mexico Coast (USGS, 2000).
Jeff Masters
Reader Comments
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IRIS Seismic Monitor
Reflector site for those at work, which now also includes Weather456, daily updates
AOI #1
AOI #2
A very elongated surface trough of low pressure that arised from an old frontal boundary.
Andres' low-level circulation is actually becoming exposed now...convection has waned drastically. I don't think there's going to be any coming back from this one.
Are you kidding? Okay, I'll check right now.
I see your little buddy burped again :)
Goodnight all.
Cheers AussieStorm
Agree with that! Levi shear forescast for that time frame support tropical development. Do anyone rember Bertha!
Nah lol that was a tectonic earthquake felt by the seismograph. It was not related to the volcano. I guess it didn't wake her....she's a deep sleeper :)
Look at the last images I posted...#60... maybe that on the far right is what might be it hinting at.
Goodnight
It definitely bears watching. This is the first time this year conditions will be even marginally favorable in the tropical Atlantic.
I told you there was a beast to the east :)
All I see is dust. Look at the RGB map.
Remember Bertha I guess it is possible!
Oh, you mean that beastly huge thing over Sudan?
Im only happy when it rains.....
Here's the MJO. See the orange starting to pop out in the central Atlantic in 10-15 days? That represents downward motion and that's what we're going to start seeing more of in that area as the season progresses. Cape Verde storms and storms forming in the MDR (Main Development Region) region will be low in number this year.
You see, that's what I was thinking. There's no way a wave like that can last that long. After all, it is still overland.
It's not the thing over Sudan...it's too far away to reach the Atlantic in 2 days. Also African waves do last that long. They form over Africa and they can last all the way to the eastern Pacific.
Well I wouldn't know that well. Meteostat imagery doesn't give images that are close enough together in time. Instead of once every 30 minutes, it's once every six hours. It's so annoying!
Hey the result of those models are the outcome of the data entered by Humans. Never when coming down to weather will be 100% accurate. The one's that believe that doesn't know what weather is about.
I will ask again,,,,,,, Is the GFS having difficulty due to the transition to El Nino?
Try This =)
So they do last that long? I don't pay very much attention to Africa, do I?
Actually that updates every 3 hours but products like this update every hour.
The tropical wave that helped spawn Andres came from Africa. So did the wave that is affecting the windward islands that 456 mentioned. They're called African Easterly Waves. As their name implies they originate over Africa and travel from the east.
That, is impressive. I just wish that was with NOAA.
Can waves come from the Indian ocean? I never saw this before.
No, disturbances and areas of low pressure within the ITCZ (intertropical convergence zone) can move through Africa from the Indian Ocean, but tropical waves only form under the special conditions over Africa, which is why they have "African" in their name. Africa is the only continent that has a large land mass in the middle of the tropics that always has the ITCZ passing through it. The instability enhanced by the African easterly jet and friction over land cause waves to form in the easterly flow south of the subtropical high, and that's how the tropical waves form.
I knew it! It can't last that long, but I do reallize that a hurricane called John in the pacific came from a wave from Africa, and traveled to the Western pacific! Once I learned that I was shocked.
Hey Levi- Not that I don't agree that Cape Verde storms will struggle this year (compared to recent post 1995 year average)... But I would like to hear your reasoning for increased subsidence for the season???
Tropical Storm "FERIA" has crossed Northern Samar and is now in the vicinity of Masbate.
Tropical Cyclone Bulletin #4
===========================
At 11:00 PM PhST, Tropical Storm Feria (Nangka) located at 12.5°N 123.6°E or in the vicinity of Masbate has 10 minutes sustained winds of 75 km/h (40 knots) with gusts of 90 km/h (50 knots).
Signal Warnings
===============
Signal Warning #2 (60-100 kph winds)
Luzon Region
-----------
1.Masbate
2.Ticao Island
3.Sorsogon
4.Albay
5.Camarines Provinces
6.Catanduanes
7.Marinduque
8.Romblon
9.Burias Island
10.Southern Quezon
11.Mindoro Provinces
12.Lubang Is.
13Batangas
14..Laguna
15.Cavite
16.Bataan
17.Rizal
18.Metro Manila
Vasayas Region
-------------
1.Samar Provinces
2.Northern Leyte
3.Camotes Is.
4.Biliran Island
5.Northern Iloilo
6.Northern Negros
7.Northern Cebu
8.Aklan
9.Capiz
Mindanao Region
----------------
1.None
Signal Warning #1 (30-60 kph winds)
Luzon Region
-----------
1.Northern Quezon
2.Polilio Island
3.Calamian group
4.Cuyo Island
5.Bulacan
6.Pampanga
7.Zambales
8.Tarlac
9.Nueva Ecija
10.1Aurora
11.Pangasinan
Visayas Region
-------------
1.Southern Leyte
2.Bohol
3.Rest of Cebu
4.Rest of Negros
5.Guimaras
6.Southern Iloilo
7.Antique
8.Siquijor
Mindanao Region
----------------
1.Surigao del Norte
2.Siargao Island
3.Dinagat Island
4.Camiguin
Additional Information
========================
Residents living in low lying,mountainous and coastal areas under storm warning signals #2 and 1 are alerted against possible flashloods, landslides and storm surges.
The public and the disaster coordinating councils concerned are advised to take appropriate actions and watch for the next bulletin to be issued at 5 A.M. tomorrow.
Tropical Cyclone Advisory #8
TROPICAL STORM NANGKA (T0904)
0:00 AM JST June 24 2009
===================================
Subject: Category One Typhoon Overland The Philippines
At 15:00 PM UTC, Tropical Storm Nangka (994 hPa) located at 12.3N 123.7E has 10 minute sustained winds of 40 knots with gusts of 60 knots. The storm is reported as moving west at 9 knots.
Gale-Force Winds
================
150 NM from the center
Dvorak Intensity:
Forecast and Intensity
=====================
24 HRS: 15.0N 120.3E - 40 knots (Tropical Storm/CAT 1)
45 HRS: 17.4N 119.9E - 45 knots (Tropical Storm/CAT 1)
69 HRS: 20.3N 119.1E - 45 knots (Tropical Storm/CAT 1)
Tropical Cyclone Warning Number FIVE
DEPRESSION ARB01-2009
17:30 PM IST June 23 2009
==================================
At 12:00 PM UTC, Depression ARB01-2009 over east central Arabian Sea moved northwestwards and lays centered near 20.5N 71.5E, or close to south Gujarat and Diu coast near Diu.
3 minute sustained winds near the center is 25 knots with a central pressure of 998 hPa. The state of the sea is rough to very rough around the system's center.
Satellite imagery indicates organization of convection during the past 12 hours. The dvorak intensity of the system is T1.5. Associated broken low/medium clouds with embedded intense to very intense convection over Arabian Sea north of 17.5N and 65.5E - 72.0E southwest of Saurstra and Kutchh.
Vertical wind shear of horizontal wind over the region is moderate (around 15-20 knots). Sea surface temperature is 0.5 to 1.0C above normal. The system lies embedded in the southwesterly flow in lower and middle levels. The upper tropospheric ridge roughly runs along 22.0N. A trough in the upper troposheric westerlies roughly run along 65.0E to the north of 20.0N
Considering all the above, the system is likely to move in a north-northeasterly direction and cross south Gujarat coast near Diu within a few hours and weaken gradually.
It's a natural byproduct of El Nino episodes, especially reactive ones where the MJO can play a big role. With El Nino you get increased upward motion in the eastern Pacific which we have been seeing lately, and downward motion (sinking air) in the western Pacific and Indian Ocean. As El Nino matures, the atmospheric patterns will fall into place and the large area of upward motion over the entire Atlantic will shrink to a more normal size over the central and eastern Pacific and sometimes the Caribbean. This will setup another region of downward motion in the central/eastern Atlantic that is more typical of an El Nino pattern. If you look at the map below, it looks logical based on geographical location alone. The pattern "Orange, green, orange, green"
Out of respect for the GFS, the conditions are expected to get rather favourable for late-June so we may very well see a couple of healthy waves in that area by next week.
Viewing: 51 - 101
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