Sea level rise: what has happened so far

By: Dr. Jeff Masters , 14:05 GMT le 10 juin 2009

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Sea level has been rising globally since the late 1700s. This rise has accelerated in recent decades, thanks to increased melting of glaciers and ice sheets due to a warmer climate, plus the fact that warmer oceans are less dense and expand, further increasing sea level. Though sea level rise appears to have slowed over the past five years, it will significantly accelerate if the climate warms the 2 - 3°C it is expected to this century. If these forecasts of a warmer world prove accurate, higher sea levels will be a formidable challenge for millions of people world-wide during the last half of this century. Sea level rise represents one of my personal top two climate change concerns (drought is the other). I'll present a series of blog posts over the coming months focusing on at-risk areas in the U.S., Caribbean, and world-wide. Today, I focus on the observed sea level rise since the Ice Age.

What's at stake
Higher sea levels mean increased storm surge inundation, coastal erosion, loss of low-lying land areas, and salt water contamination of underground drinking water supplies. About 44% of the Earth's 6.7 billion people live within 150 km (93 miles) of the coast, and 600 million people live at an elevation less than ten meters (33 feet). Eight of the ten largest cities in the world are sited on the ocean coast. In the U.S., the coastal population has doubled over the past 50 years. Fourteen of the twenty largest urban centers are located within 100 km of the coast, and are less than ten meters above sea level (McGranahan et al., 2007). The population of many vulnerable coastal regions are expected to double by 2050, according to the U.S. Census Bureau.

Sea level rise since the Ice Age
Before the most recent Ice Age, sea level was about 4 - 6 meters (13 - 20 feet) higher than at present. Then, during the Ice Age, sea level dropped 120 meters (395 ft) as water evaporated from the oceans precipitated out onto the great land-based ice sheets. The former ocean water remained frozen in those ice sheets during the Ice Age, but began being released 12,000 - 15,000 years ago as the Ice Age ended and the climate warmed. Sea level increased about 115 meters over a several thousand year period, rising 40 mm/year (1.6"/yr) during one 500-year pulse of melting 14,600 years ago. The rate of sea level rise slowed to 11 mm/year (0.43"/yr) during the period 7,000 - 14,000 years ago (Bard et al., 1996), then further slowed to 0.5 mm/yr 6,000 - 3,000 years ago. About 2,000 - 3,000 years ago, the sea level stopped rising, and remained fairly steady until the late 1700s (IPCC 2007). One exception to this occurred during the Medieval Warm Period of 1100 - 1200 A.D., when warm conditions similar to today's climate caused the sea level to rise 5 - 8" (12 - 21 cm) higher than present (Grinsted et al., 2008). This was probably the highest the sea has been since the beginning of the Ice Age, 110,000 years ago. There is a fair bit of uncertainty in all these estimates, since we don't have direct measurements of the sea level.


Figure 1. Global sea level from 200 A.D. to 2000, as reconstructed from proxy records of sea level by Moberg et al. 2005. The thick black line is reconstructed sea level using tide gauges (Jevrejeva, 2006). The lightest gray shading shows the 5 - 95% uncertainty in the estimates, and the medium gray shading denotes the one standard deviation error estimate. The highest global sea level of the past 110,000 years likely occurred during the Medieval Warm Period of 1100 - 1200 A.D., when warm conditions similar to today's climate caused the sea level to rise 5 - 8" (12 - 21 cm) higher than present. Image credit: Grinsted, A., J.C. Moore, and S. Jevrejeva, 2009, "Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD", Climate Dynamics, DOI 10.1007/s00382-008-0507-2, 06 January 2009.

Sea level rise over the past 300 years
Direct measurements of sea level using tide gauges began in Amsterdam in 1700. Additional tide gauges began recording data in Liverpool, England in 1768 and in Stockholm, Sweden in 1774. These gauges suggest that a steady acceleration of sea rise of 0.01 mm per year squared began in the late 1700s, resulting in a rise in sea level of 2.4" (6 cm, 0.6 mm/yr) during the 19th century and 7.5" (19 cm, 1.9 mm/yr) during the 20th century (Jevrejeva et al., 2008). There is considerable uncertainty in just how much sea level rise has occurred over the past few centuries, though. Measuring global average sea level rise is a very tricky business. For starters, one must account for the tides, which depend on the positions of the Earth and Moon on a cycle that repeats itself once every 18.6 years. Tide gauges are scattered, with varying lengths of record. The data must be corrected since land is sinking in some regions, due to pumping of ground water, oil and gas extraction, and natural compaction of sediments. Also, the land is rising in other regions, such as Northern Europe, where it is rebounding from the lost weight of the melted glaciers that covered the region during the last Ice Age. Ocean currents, precipitation, and evaporation can cause a 20 inch (50 cm) difference in sea level in different portions of the ocean. As a result of all this uncertainty, the 1996 Intergovernmental Panel on Climate Change (IPCC) report gave a range of 4 - 10" (10 - 25 cm) for the observed sea level rise of the 20th century. The 2007 IPCC report narrowed this range a bit, to 5 - 9" (12 - 22 cm), or 1.2 - 2.2 mm/year. Rates of sea level rise are much higher in many regions. In the U.S., the highest rates of sea-level rise are along the Mississippi Delta region--over 10 mm/yr, or 1 inch/2.5 years (USGS, 2006). This large relative rise is due, in large part, to the fact that the land is sinking.


Figure 2. Absolute sea level rise between 1955 and 2003 as computed from tide gauges and satellite imagery data. The data has been corrected for the rising or sinking of land due to crustal motions or subsidence of the land, so the relative sea level rise along the coast will be different than this. The total rise (in inches) for the 48-year period is given in the top scale, and the rate in mm/year is given in the bottom scale. The regional sea level variations shown here resulted not only from the input of additional water from melting of glaciers and ice caps, but also from changes in ocean temperature and density, as well as changes in precipitation, ocean currents, and river discharge. Image credit: IPCC, 2007

Sea level rise over the past 15 years
According to the Intergovernmental Panel on Climate Change (IPCC) 2007 report, sea level accelerated from the 1.2 - 2.2 mm/yr observed during the 20th century to 3.1 mm/year during the period 1993 - 2003. These estimates come from high resolution measurements from satellite radar altimeters, which began in 1992. Tide gauges showed a similar level of sea level rise during that ten-year period. The IPCC attributed more than half of this rise (1.6 mm/yr) to the fact that the ocean expanded in size due to increased temperatures. Another 1.2 mm/yr rise came from melting of Greenland, West Antarctica, and other land-based ice, and about 10% of the rise was unaccounted for. However, during the period 2003 - 2008, sea level rise slowed to 2.5 mm/year, according to measurements of Earth's gravity from the GRACE satellites (Cazenave et al., 2008). This reduction in sea level rise probably occurred because ocean sea surface temperatures have not warmed since 2003 (Figure 3). The authors concluded that sea level rise due to ocean warming decreased more than a factor of five from 2003 - 2008, compared to 1993 - 2003, contributing only 0.3 mm/yr vs. the 1.6 mm/yr previously.


Figure 3. Global average sea surface temperatures (SSTs) from 1990-2008. SSTs have not increased in the past seven years. Image credit: NASA/GISS.

For more information
The best source of information I found while compiling my sea level pages was the Coastal Sensitivity to Sea-Level Rise: A Focus on the Mid-Atlantic Region report by the U.S. Climate Science Program. It has a huge number of references to all the latest science being done on sea level rise.

References
Bard, E., et al., 1996, "Sea level record from Tahiti corals and the timing of deglacial meltwater discharge", Nature 382, pp241-244, doi:10.1038/382241a0.

Cazenave et al., 2008, "Sea level budget over 2003-2008: A reevaluation from satellite altimetry and Argo", Global and Planetary Change, 2008; DOI:10.1016/j.gloplacha.2008.10.004

Grinsted, A., J.C. Moore, and S. Jevrejeva, 2009, "Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD", Climate Dynamics, DOI 10.1007/s00382-008-0507-2, 06 January 2009.

IPCC (Intergovernmental Panel on Climate Change), 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, UK, and New York, 996 pp.

Jevrejeva, S., J.C. Moore, A. Grinsted,, and P.L. Woodworth, 2008, "Recent global sea level acceleration started over 200 years ago?", Geophysical Research Letters, 35, L08715, doi:10.1029/2008GL033611, 2008.

McGranahan, G., D. Balk, and B. Anderson, 2007, "The rising tide: assessing the risks of climate change and human settlements in low elevation coastal zones", Environment & Urbanization, 19(1), 17-37.

Moberg, A., et al., 2005, "Highly variable northern hemisphere temperature reconstructed from low- and high-resolution proxy data", Nature 433, pp613-617, doi:10.1038/nature03265.

United States Geological Survey (USGS), 2006, National Assessment of Coastal Vulnerability to Sea-Level Rise: Preliminary Results for the U.S. Gulf of Mexico Coast, U.S. Geological Survey Open-File Report 00-179.

Tropical update
The tropical Atlantic is quiet, and the only region worth watching is the Western Caribbean, which could see formation of a tropical disturbance with heavy thunderstorm activity this weekend.

Jeff Masters

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Quoting jeffs713:


If I remember by college physics well enough, the amount of radiation is the inverse of the square of the distance between the area being measured and the radiation source.

So if you have a satellite orbiting 150 miles above the surface (just to make the math manageable), and you measure the wattage at 1 meter from the source... the amount of radiation at the surface of the planet would be about 1/59049000000th the energy (150 miles = 243km) . To put it in perspective... a 1,000,000W source at 150 miles up would have a radiation level of .0000169th of a watt on the ground.
Would the frequency not have to be part of the equation?
Member Since: 12 juin 2005 Posts: 6 Comments: 8185
Quoting stormwatcherCI:
But will it hold together ? I REALLY need to know what to expect given that I am just about in the direct path .

In the path of what? Something that doesn't exist yet as a tropical entity?
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Quoting Hurricane4Lex:
How do you get these models again? I've completely forgotten :( Sorry and TIA


Stormjunkie and Hurricane23 have great links on their blogs. Just choose blogs at the top & search by name. Or wait until they post and click on their name.
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Quoting stormwatcherCI:
But will it hold together ? I REALLY need to know what to expect given that I am just about in the direct path .


No significant development of low feature is expected during the next 48 hrs. Probably the low will enhanced additional showers in the vicinity. By 72 hrs, the guidance has it in the northwest corner of the Caribbean west of the island, so I do believe significant development of this feature to threaten Jamaica due to upper winds. The biggest effect will be moisture.
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Google Tropical Models..

You'll get'um all..


Results 1 - 10 of about 3,910,000 for tropical Models. (0.19 seconds)
Member Since: 3 juillet 2005 Posts: 421 Comments: 127679
How do you get these models again? I've completely forgotten :( Sorry and TIA
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Early model consensus = we watch this area closely for "possible" development but not even close yet.... (No Cigar but perhaps a few slices of Pizza while we watch and wait would be appropriate)....
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Quoting stormwatcherCI:
But will it hold together ? I REALLY need to know what to expect given that I am just about in the direct path .


The 18z NAM
degenerate it, and then reinvigorate it, as conditions become less hostile.


Member Since: 19 juillet 2008 Posts: 43 Comments: 4051
Current Western Caribbean Environment

Photobucket

Now that we may be seeing better model consensus, we should begin watching for the evolution to occur. Right now, you can clearly see the upper-level trough digging into the Northwest Caribbean that could play a significant role in a few days. According to the models, the trough cuts off in the same area and forms an upper-level low that moves into the Yucatan Peninsula. Once this occurs, wind shear will become more favorable for possible tropical development. As this happens, the trough gets replaced with a deep-layered ridge that stretches across the Gulf of Mexico and Atlantic.

Now, this tropical wave currently migrating across the Western Caribbean could serve as a catalyst for some development. Combined with the lingering surface trough across the Western Caribbean, there could conceivably be some development. It will all depend on how the two features interact with each other and whether the upper-level pattern unfolds as shown by computer models.

Since we don't have an actual disturbance to track at this time, it would be too soon to speculate as to where and how strong any such potential system would get. But, given the latest trends with the computer models and discussions by the TPC, its seeming more likely that there could be some tropical development occuring in the Western Caribbean in a few days.
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Quoting WeatherStudent:


Good afternoon all. FM, how extraordinarily rare would this type of potential track for a TC to take in June be? This would be a first, wouldn't it? So, South Florida appears to be in the all clear from this critter then?


Not at all unusual. Its on the southern edge of the climalogically active area for June, but nothing absurdly crazy (like a June Cape Verde hurricane).
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Quoting WeatherStudent:


Good afternoon all. FM, how extraordinarily rare would this type of potential track for a TC to take in June be? This would be a first, wouldn't it? So, South Florida appears to be in the all clear from this critter then?


Despite the model consensus, I do not think any is out of the woods. LOL Nothing has even formed yet.

Who knows...who knows
Member Since: 19 juillet 2008 Posts: 43 Comments: 4051
Quoting Weather456:
A 1009 mb low has form in the SW Caribbean

But will it hold together ? I REALLY need to know what to expect given that I am just about in the direct path .
Member Since: 9 octobre 2008 Posts: 0 Comments: 8282
Quoting Ossqss:
256, Microwaves, not light waves @ 24x7x365 x how many Sat's over how many years ?
Logic tells me it has to have some effect, but cow exhaust is more interesting :)
Let alone all of the wireless land based networks and cell towers etc, uplinks to the media sat's.

I just really want to know what impact this technology has had since it has propagated significantly and done so in direct correlation with most of the timelines relating to the factors associated with climate change.

Typical microwave oven 2.45 ghz 1000w

Quicksat - from the link
Radar: 13.4 gigahertz; 110-watt pulse at 189-hertz pulse repetition frequency (PRF)

I can't do that math or find anything relating to the impact of man made radiation on our environment or atmosphere. Can you?



If I remember by college physics well enough, the amount of radiation is the inverse of the square of the distance between the area being measured and the radiation source.

So if you have a satellite orbiting 150 miles above the surface (just to make the math manageable), and you measure the wattage at 1 meter from the source... the amount of radiation at the surface of the planet would be about 1/59049000000th the energy (150 miles = 243km) . To put it in perspective... a 1,000,000W source at 150 miles up would have a radiation level of .0000169th of a watt on the ground.
Member Since: Posts: Comments:
The Best Pizza Dough Recipe ..Im using it tonight.

I add 2 tsp Italian Seasoning to the flour first.



Dats just the way I roll,..ya'll..


Member Since: 3 juillet 2005 Posts: 421 Comments: 127679
Quoting NRAamy:
Global warming, the tropics, and football?

all we need is some pizza...Pat, can you hook us up?

:)


Er, ah, beverages of choice?
Member Since: 12 juin 2005 Posts: 6 Comments: 8185
A westward path toward the GOM is currently the mostly likely scenario at the moment, as the A/B anticyclone invigorates; a developing high pressure system in the eastern U.S should further contribute to the westward motion. The 12z GFS however delays the intensification of the Highs, and expects them to build near the end of next week. Thus, the GFS favors a more northerly track; I think there will some changes in its forecast at 18z.
Member Since: 19 juillet 2008 Posts: 43 Comments: 4051
Global warming, the tropics, and football?

all we need is some pizza...Pat, can you hook us up?

:)
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A 1009 mb low has form in the SW Caribbean

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12Z CMC..WNW

Member Since: 3 juillet 2005 Posts: 421 Comments: 127679
Hi all what did I miss with our carribean disturbance that we've been watching for 3-4 days?
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Quoting canesrule1:


Is there a reason you quote yourself?
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Quoting futuremet:
The models are establishing the best consensus so far I've seen this week.


True, I'm somewhat surprise because I was going on 2 models for a while now.
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303. IKE
Quoting Patrap:
Puts that sucka due South of yas IKE.

Way to early fer wearing and Tearing...


But there's a high to it's north that is suppose to really build in next week.
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Good afternoon everyone.

Global warming, the tropics, and football?
Since I don't know much about the fist, have no luck with the second, and I'm a Cowboy fan, so what could I know about the third. Maybe I'll just observe today. LOL.
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301. IKE
Quoting futuremet:
The models are establishing the best consensus so far I've seen this week.


Agree.

See what the GFS spits out soon. It feel off on the low in the 12Z run.
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Puts that sucka due South of yas IKE.

Way to early fer wearing and Tearing...
Member Since: 3 juillet 2005 Posts: 421 Comments: 127679
The models are establishing the best consensus so far I've seen this week.
Member Since: 19 juillet 2008 Posts: 43 Comments: 4051
298. IKE
18Z NAM @ 84 hours....looks like TS Ana....

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ESL By LSU

Member Since: 3 juillet 2005 Posts: 421 Comments: 127679
Quoting Buhdog:
Levi....why then green shading when none there earlier? I obvioulsy visually see no swirl...just saw it on the map and it looked to have vorticity there.....Thanks


It's a very low variance in vorticity......I mean it could be caused by almost anything. The tail-end of a surface trough is over south Florida; maybe that's what is causing it. It's nothing significant.

Back later.
Member Since: Posts: Comments:
256, Microwaves, not light waves @ 24x7x365 x how many Sat's over how many years ?
Logic tells me it has to have some effect, but cow exhaust is more interesting :)
Let alone all of the wireless land based networks and cell towers etc, uplinks to the media sat's.

I just really want to know what impact this technology has had since it has propagated significantly and done so in direct correlation with most of the timelines relating to the factors associated with climate change.

Typical microwave oven 2.45 ghz 1000w

Quicksat - from the link
Radar: 13.4 gigahertz; 110-watt pulse at 189-hertz pulse repetition frequency (PRF)

I can't do that math or find anything relating to the impact of man made radiation on our environment or atmosphere. Can you?

I can only find stuff like this

Link
Member Since: 12 juin 2005 Posts: 6 Comments: 8185
Quoting Hurricajun:
I'll actually be at Children's again sometime in August, so I'll have to swing by because if I remember correctly from last year you ain't that far!


Were Just Half Mile up Tchoupitoulas Street from the Hospital.
Member Since: 3 juillet 2005 Posts: 421 Comments: 127679
Quoting dutchessweather:
In response to someone who said something of the order of "why not try to prevent global warming/sea-level rise...we've done all sorts of environmental damage in the past...etc."

The trouble is, there is almost no chance of stopping whatever is causing the warming, and the efforts to try and stop it will kill the U.S. economy (our present situation is rosy compared to what would happen if Al Gore and his cronies got what they want). The whole man-made-global warming/climate change issue is political. Those who want to destroy the U.S. see it as a way to meet that goal. There are many bad people out there who want the U.S. to be just another European state. By killing our economy, we would be forced to be subservient to other forces/entities out there. Global warming would probably benefit the U.S.; longer growing seasons, lower heating costs, etc. The downside would possibly be greater rates of sea level rise (greater than what has been going on for 18,000 years), but we're pretty smart, and could deal with it.

Well, if you just totally eliminate all "non-green" jobs, it darn well would nuke our economy (strike that - the WORLD economy) back into the stone age (figuratively). A better solution would be to make sustainable development as attractive as "normal" development, and make sustainability a valid option. The company I work for is the world's largest container shipping line. We don't exactly have a zero carbon footprint. What we are doing (as are many other companies) is reducing that footprint, and looking at how we can make our business more sustainable. The US or world economy can hardly turn on a dime, but it can be steered. The steering does not have to be taking a hairpin turn at 200mph. It can be gentle and controlled, and put the planet onto a better path without breaking anything or ruining any economies.
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Area forecast discussion
National Weather Service New Orleans la
303 PM CDT Wednesday Jun 10 2009


Yesterday/S forecast indicated a slight chance of showers and
thunderstorms across the northern half of the area on Saturday. It
appears that such a forecast was wishful thinking. All major
models now indicate the vorticity maximum that was previously
forecast to clip our local forecast area will now remain well
to our north...along with all of the other fast-moving shortwave
disturbances.


Unless something forces this high out of the area...expect dry
conditions to continue and afternoon temperatures to maintain
their current levels in the middle 90s or even climb slowly higher as
the ground dries further.
Member Since: 3 juillet 2005 Posts: 421 Comments: 127679
I'll actually be at Children's again sometime in August, so I'll have to swing by because if I remember correctly from last year you ain't that far!
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After reviewing the 12Z model runs, it seems, the models are becoming in more agreement with the formation of a tropical disturbance in the southwest Caribbean with the CMC having the strongest solutions. The average steering flow of all models (model spread) indicate that as the trough secludes over the NW Caribbean, a deep layer ridge will petrude over the Southern USA favoring a westward motion. The GFS is furthest east indicating the cyclone will follow frontal weakness. The former seems more likely.
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a really good book--- The Frozen Thames by Helen Humphries, an international bestseller now. Reminds me of this blog. It is a collection of very very short stories of each time in history the Thames River actually froze solid. Most of them start out with "It was the coldest winter anyone had ever seen". but you just wonder, what caused those terrible cold spells. The first time is 1122 and the last time is 1927. 1929 was a bad year for flooding here in the US... maybe it was el nino or something?
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Well, I know he was a good football player, but... his head is so big now he NEEDS a box to carry it in! lol Yeah, the gumbo is good, next time I am up your way I'll drop you some off!!


Bobby Loves to bring up the Game in 77. He does too much radio now.
He's a lot Greyer than me too..
LOL


Good deal,..we just finished up the last of Last night Crawfish etoufee. Twas killa.

Always Lub another Persons Gumbo.
Specially from Cutoff..!
Member Since: 3 juillet 2005 Posts: 421 Comments: 127679
286. IKE
Quoting kimoskee:
Hey guys please help me out. I'm volunteering with a large outdoor fundraiser for cancer on Saturday in Kingston, Jamaica. Should we be planning for a gentle shower or a monsoon?


If you believe the 18Z NAM @ 66 hours, it(93L?), should be mainly west of you by Saturday....



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Quoting Patrap:



We lost the High School State Championship to S Lafourche in 77 in Their Stadium.
Nov.or Dec 77

I am a Bonnabel Bruin.

Tommy Wilcox,who Played for Jim Mora in the USFL was our Quarterback.

Cutoff nice Folks. Good Gumbo too.





Well, I know he was a good football player, but... his head is so big now he NEEDS a box to carry it in! lol Yeah, the gumbo is good, next time I am up your way I'll drop you some off!!
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Good Afternon;

Tropical Update
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282. IKE
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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.

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