Eyewall replacement cycle 1

Eyewall replacement cycleEyewall replacement cycles, also called concentric eyewall cycles, naturally occur in intense tropical cyclones,generally with winds greater than 185 km/h (115 mph), or major hurricanes (Category 3 or above). When tropicalcyclones reach this intensity, and the eyewall contracts or is already sufficiently small, some of the outer rainbandsmay strengthen and organize into a ring of thunderstorms—an outer eyewall—that slowly moves inward and robsthe inner eyewall of its needed moisture and angular momentum. Since the strongest winds are in a cyclone'seyewall, the tropical cyclone usually weakens during this phase, as the inner wall is "choked" by the outer wall.Eventually the outer eyewall replaces the inner one completely, and the storm may re-intensify.The discovery of this process was partially responsible for the end of the U.S. government's hurricane modificationexperiment Project Stormfury. This project set out to seed clouds outside the eyewall, causing a new eyewall to formand weakening the storm. When it was discovered that this was a natural process due to hurricane dynamics, theproject was quickly abandoned.[]

Almost every intense hurricane undergoes at least one of these cycles during its existence. Recent studies haveshown that nearly half of all tropical cyclones, and nearly all cyclones with sustained winds over 204 kilometres perhour (127 mph; 110 kn), undergo eyewall replacement cycles.[] Hurricane Allen in 1980 went through repeatedeyewall replacement cycles, fluctuating between Category 5 and Category 3 status on the Saffir-Simpson HurricaneScale several times. Hurricane Juliette (2001) was a rare documented case of triple eyewalls.[] Typhoon June (1975)was the first reported case of triple eyewalls.[] The reconnaissance flight that observed the triple concentric eyewallsalso recorded that this was the strongest typhoon up to that point.[1]

History

1966 photo of the crew and personnel of ProjectStormfury.

The first tropical system to be observed with concentric eyewalls wasTyphoon Sarah by Fortner in 1956, which he described as "an eyewithin an eye".[] The storm was observed by a reconnaissance aircraftto have an inner eyewall at 6 kilometres (3.7 mi) and an outer eyewallat 28 kilometres (17 mi). During a subsequent flight 8 hours later, theinner eyewall had disappeared, the outer eyewall had reduced to 16kilometres (9.9 mi) and the maximum sustained winds and hurricaneintensity had decreased.[] The next hurricane observed to haveconcentric eyewalls was Hurricane Donna in 1960.[] Radar fromreconnaissance aircraft showed an inner eye that varied from 10 miles(16 km) at low altitude to 13 miles (21 km) near the tropopause. Inbetween the two eyewalls was an area of clear skies that extendedvertically from 3,000 feet (910 m) to 25,000 feet (7,600 m). The low-level clouds at around 3,000 feet (910 m) weredescribed as stratocumulus with concentric horizontal rolls. The inner eyewall was reported to reach heights near45,000 feet (14,000 m) while the inner eyewall only extended to 30,000 feet (9,100 m). 12 hours after identifying aconcentric eyewalls, the inner eyewall had dissipated.[]

Hurricane Beulah in 1967 was the first tropical cyclone to have its eyewall replacement cycle observed frombeginning to end.[] Previous observations of concentric eyewalls were from aircraft-based platforms. Beulah wasobserved from the Puerto Rico land-based radar for 34 hours during which time a double eyewall formed anddissipated. It was noted that Beulah reached maximum intensity immediately prior to undergoing the eyewallreplacement cycle, and that it was "probably more than a coincidence."[] Previous eyewall replacement cycles hadbeen observed to decrease the intensity of the storm,[] but at this time the dynamics of why it occurred was notknown.[citation needed]

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As early as 1946 it was known that the introduction of carbon dioxide ice or silver iodide into clouds that containedsupercooled water would convert the liquid water into ice. Today this is known as the Bergeron–Findeisen process.It was thought that scientists could manipulate the size of the snow or ice particles to be either larger or smaller thanthe original liquid water, and would either result in increased or decreased precipitation. By increasing the rate ofprecipitation, the seeded cloud would result in dissipation of the storm.[] By early 1960, the working theory was thatthe eyewall of a hurricane was inertially unstable and that the clouds had a large amount of supercooled water.Therefore, seeding the storm outside the eyewall would release more latent heat and cause the eyewall to expand.The expansion of the eyewall would be accompanied with a decrease in the maximum wind speed thoughconservation of angular momentum.[]

Project StormfuryProject Stormfury was an attempt to weaken tropical cyclones by flying aircraft into them and seeding with silveriodide. The project was run by the United States Government from 1962 to 1983.[]

The hypothesis was that the silver iodide would cause supercooled water in the storm to freeze, disrupting the innerstructure of the hurricane. This led to the seeding of several Atlantic hurricanes. However, it was later shown thatthis hypothesis was incorrect.[] In reality, it was determined most hurricanes do not contain enough supercooledwater for cloud seeding to be effective. Additionally, researchers found that unseeded hurricanes often undergo thesame structural changes that were expected from seeded hurricanes. This finding called Stormfury's successes intoquestion, as the changes reported now had a natural explanation.[]

The last experimental flight was flown in 1971, due to a lack of candidate storms and a changeover in NOAA's fleet.More than a decade after the last modification experiment, Project Stormfury was officially canceled. Although afailure in its goal of reducing the destructiveness of hurricanes, Project Stormfury was not without merit. Theobservational data and storm lifecycle research generated by Stormfury helped improve meteorologists' ability toforecast the movement and intensity of future hurricanes.[]

Secondary eyewall formation

Imagery from Tropical Rainfall MeasuringMission shows the beginning of an eyewall

replacement cycle in Hurricane Frances.

Secondary eyewalls were once considered a rare phenomenon. Sincethe advent of reconnaissance airplanes and microwave satellite data, ithas been observed that over half of all major tropical cyclones developat least one secondary eyewall.[][] There have been many hypothesesthat attempt to explain the formation of secondary eyewalls. Thereason why hurricanes develop secondary eyewalls is not wellunderstood.[]

Identification

Qualitatively identifying secondary eyewalls is easy for a hurricaneanalyst to do. It involves looking at satellite or RADAR imagery andseeing if there are two concentric rings of enhanced convection. Theouter eyewall is generally almost circular and concentric with the innereyewall. Quantitative analysis is more difficult since there exists noobjective definition of what a secondary eyewall is. Kossin et al.. specified that the outer ring had to be visiblyseparated from the inner eye with at least 75% closed with a moat region clear of clouds.[]

Eyewall replacement cycle 3

Typhoon Chanchu at peak intensity, during aneyewall replacement cycle

While secondary eyewalls have been seen as a tropical cyclone isnearing land, none have been observed while the eye is not over theocean. July offers the best background environmental conditions fordevelopment of a secondary eyewall. Changes in the intensity of stronghurricanes such as Katrina, Ophelia, and Rita occurred simultaneouslywith eyewall replacement cycles and comprised interactions betweenthe eyewalls, rainbands and outside environments.[][] Eyewallreplacement cycles, such as occurred in Katrina as it approached theGulf Coast of the United States, can greatly increase the size of tropicalcyclones while simultaneously decreasing in strength.[2]

During the period from 1997–2006, 45 eyewall replacement cycleswere observed in the tropical North Atlantic Ocean, 12 in the EasternNorth Pacific and 2 in the Western North Pacific. 12% of all Atlanticstorms and 5% of storm in the Pacific underwent eyewall replacementduring this time period. In the North Atlantic, 70% of major hurricaneshad at least one eyewall replacement, compared to 33% of all storms.In the Pacific, 33% of major hurricanes and 16% of all hurricanes hadan eyewall replacement cycle. Stronger storms have a higher probability of forming a secondary eyewall, with 60%of category 5 hurricanes underwent an eyewall replacement cycle within 12 hours.[]

During the years 1969-1971, 93 storms reached tropical storm strength or greater in the Pacific Ocean. 8 of the 15that reached super typhoon strength (65 m/s), 11 of the 49 storms that reached typhoon strength (33 m/s), and noneof the 29 tropical storms (<33 m/s) developed concentric eyewalls. The authors note that because the reconnaissanceaircraft were not specifically looking for double eyewall features, these numbers are likely underestimates.[]

During the years 1949-1983, 1268 typhoons were observed in the Western Pacific. 76 of these had concentriceyewalls. Of all the typhoons that underwent eyewall replacement, around 60% did so only once; 40% had more thanone eyewall replacement cycle, with two of the typhoons each experiencing five eyewall replacements. The numberof storms with eyewall replacement cycles was strongly correlated with the strength of the storm. Stronger typhoonswere much more likely to have concentric eyewalls. There were no cases of double eyewalls where the maximumsustained wind was less than 45 m/s or the minimum pressure was higher than 970 hPa. More than three-quarters ofthe typhoons that had pressures lower than 870 hPa developed the double eyewall feature. The majority of Westernand Central Pacific typhoons that experience double eyewalls do so in the vicinity of Guam.[]

Early formation hypothesesSince eyewall replacement cycles were discovered to be natural, there has been a strong interest in trying to identifywhat causes them. There have been many hypotheses put forth that are now abandoned. In 1980, Hurricane Allencrossed the mountainous region of Haiti and simultaneously developed a secondary eyewall. Hawkins noted this andhypothesized that the secondary eyewall may have been caused by topographic forcing.[] Willoughby suggested thata resonance between the inertial period and asymmetric friction may be the cause of secondary eyewalls.[3] Latermodeling studies and observations have shown that outer eyewalls may develop in areas uninfluenced by landprocesses.There have been many hypotheses suggesting a link between synoptic scale features and secondary eyewall replacement. It has been observed that radially inward traveling wave-like disturbances have preceded the rapid development of tropical disturbances to tropical cyclones. It has been hypothesized that this synoptic scale internal forcing could lead to a secondary eyewall.[] Rapid deepening of the tropical low in connection with synoptic scale forcing has been observed in multiple storms,[] but has been shown to not be a necessary condition for the formation

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of a secondary eyewall.[] The wind-induced surface heat exchange (WISHE) is a positive feedback mechanismbetween the ocean and atmosphere in which a stronger ocean-to-atmosphere heat flux results in a strongeratmospheric circulation, which results in a strong heat flux.[] WISHE has been proposed as a method of generatingsecondary eyewalls.[] Later work has shown that while WISHE is a necessary condition to amplify disturbances, it isnot needed to generate them.[]

Vortex Rossby wave hypothesisIn the vortex Rossby wave hypothesis, the waves travel radially outward from the inner vortex. The waves amplifyangular momentum at a radius that is dependent on the radial velocity matching that of the outside flow. At thispoint, the two are phase-locked and allow the coalescence of the waves to form a secondary eyewall.[][]

β-skirt axisymmetrization hypothesisIn a fluid system, β (beta) is the spatial, usually horizontal, change in the environmental vertical vorticity. β ismaximized in the eyewall of a tropical cyclone. The β-skirt axisymmetrization (BSA) assumes that a tropical cycloneabout develop a secondary eye will have a decreasing, but non-negative β that extends from the eyewall toapproximately 50 kilometres (31 mi) to 100 kilometres (62 mi) from the eyewall. In this region, there is a small, butimportant β. This area is called the β-skirt. Outward of the skirt, β is effectively zero.[]

Convective available potential energy (CAPE) is the amount of energy a parcel of air would have if lifted a certaindistance vertically through the atmosphere. The higher the CAPE, the more likely there will be convection. If areasof high CAPE exist in the β-skirt, the deep convection that forms would act as a source of vorticity and turbulencekinetic energy. This small-scale energy will upscale into a jet around the storm. The low-level jet focuses thestochastic energy a nearly axisymmetric ring around the eye. Once this low-level jet forms, a positive feedback cyclesuch as WISHE can amplify the initial perturbations into a secondary eyewall.[][]

Death of the inner eyewall

After the secondary eyewall totally surrounds the innereyewall, it begins to affect the tropical cyclonedynamics. Hurricanes are fueled by the high oceantemperature. Sea surface temperatures immediatelyunderneath a tropical cyclone can be several degreescooler than those at the periphery of a storm, andtherefore cyclones are dependent upon receiving theenergy from the ocean from the inward spiraling winds.When an outer eyewall is formed, the moisture andangular momentum necessary for the maintenance of the inner eyewall is now being used to sustain the outereyewall, causing the inner eye to weaken and dissipate leaving the tropical cyclone with one eye that is larger indiameter than the previous eye.In the moat region between the inner and outer eyewall, observations by dropsondes have shown high temperaturesand dewpoint depressions. The eyewall contracts because of inertial instability.[] Contraction of the eyewall occurs ifthe area of convection occurs outside the radius of maximum winds. After the outer eyewall forms, subsidenceincreases rapidly in the moat region.[]

Once the inner eyewall dissipates, the storm weakens; the central pressure increases and the maximum sustained windspeed decreases. Usually the new eyewall will contract and intensify the storm such that it is stronger than before the start of the eyewall replacement cycle. Rapid changes in the intensity of tropical cyclones is a typical characteristic of eyewall replacement cycles.[] Compared to the processes involved with the formation of the

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secondary eyewall, the death of the inner eyewall is fairly well understood.Some tropical cyclones with extremely large outer eyewalls do not experience the contraction of the outer eye andsubsequent dissipation of the inner eye. Typhoon Winnie (1997) developed an outer eyewall with a diameter of 200kilometres (120 mi) that did not dissipate until it reached the shoreline.[] The time required for the eyewall tocollapse is inversely related to the diameter of the eyewall which is mostly because inward directed wind decreasesasymptotically to zero with distance from the radius of maximum winds, but also due to the distance required tocollapse the eyewall.[]

Throughout the entire vertical layer of the moat, there is dry descending air. The dynamics of the moat region aresimilar to the eye, while the outer eyewall takes on the dynamics of the primary eyewall. The vertical structure of theeye has two layers. The largest layer is that from the top of the tropopause to a capping layer around 700 hPa whichis described by descending warm air. Below the capping layer, the air is moist and has convection with the presenceof stratocumulus clouds. The moat gradually takes on the characteristics of the eye, upon which the inner eyewallcan only dissipate in strength as the majority of the inflow is now being used to maintain the outer eyewall. Theinner eye is eventually evaporated as it is warmed by the surrounding dry air in the moat and eye. Models andobservations show that once the outer eyewall completely surrounds the inner eye, it takes less than 12 hours for thecomplete dissipation of the inner eyewall. The inner eyewall feeds mostly upon the moist air in the lower portion ofthe eye before evaporating.[]

Evolution into an annular hurricaneAnnular hurricanes have a single eyewall that is larger and circularly symmetric. Observations show that an eyewallreplacement cycle can lead to the development of an annular hurricane. While some hurricanes develop into annularhurricanes without an eyewall replacement, it has been hypothesized that the dynamics leading to the formation of asecondary eyewall may be similar to those needed for development of an annular eye.[] Hurricane Daniel (2006) wasan example where a storm had an eyewall replacement cycle and then turned into an annular hurricane.[] Annularhurricanes have been simulated that have gone through the life cycle of an eyewall replacement. The simulationsshow that the major rainbands will grow such that the arms will overlap, and then it spiral into itself to form aconcentric eyewall. The inner eyewall dissipates, leaving a hurricane with a singular large eye with no rainbands.[]

References

Further reading

Books• Paul V. Kislow (2008). Hurricanes: background, history and bibliography. Nova Publishers. p. 50.

ISBN 1-59454-727-0.• Kshudiram Saha (2009). Tropical Circulation Systems and Monsoons. Springer. p. 76. ISBN 3-642-03372-5.

Web pages• "Satellite examples of eyewall replacement cycles" (http:/ / cimss. ssec. wisc. edu/ goes/ blog/ ?s=eyewall+

replacement+ cycle). CIMSS Satellite Blog. Retrieved 28 August 2010.• Jeff Haby. "Answers: How hurricanes replace their eyewalls" (http:/ / www. theweatherprediction. com/

habyhints2/ 412/ ). Haby's Weather Forecasting Hints. Retrieved 19 November 2009.• Chris Cappella (31 August 2004). "Answers: How hurricanes replace their eyewalls" (http:/ / www. usatoday.

com/ weather/ resources/ askjack/ 2003-11-15-eyewall-replacement_x. htm). USA Today. Retrieved 19 November2009.

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• R.L. Deal (20 April 2006). "Eye Wall Replacement In Tropical Cyclones" (http:/ / casil. met. fsu. edu/ ~rdeal/documents/ Deal_Met3300. pdf) (PDF). MET3300 Project. The Florida State University. Retrieved 19 November2009.

• "Eyewall Replacement Cycles" (http:/ / www. meted. ucar. edu/ tropical/ textbook/ ch10/ tropcyclone_10_4_5_3.html). (Requires free registration). University Corporation for Atmospheric Research. 2007. Retrieved 19November 2009.

• J.P. Kossin and D.S. Nolan. "Tropical Cyclone Structure and Intensity Change Related to Eyewall ReplacementCycles and Annular Storm Formation, Utilizing Objective Interpretation of Satellite Data and Model Analyses"(http:/ / www. onr. navy. mil/ sci_tech/ 32/ reports/ docs/ 07/ mmkossin. pdf) (PDF). Retrieved 19 November2009.

• Jon Hamilton (1 March 2007). "Why Katrina Became a Monster and Rita Fizzled" (http:/ / www. npr. org/templates/ story/ story. php?storyId=7672274). All Things Considered. National Public Radio. Retrieved 19November 2009.

Journal articles• Willoughby, H. E. (1979). "Forced Secondary Circulations in Hurricanes". J. Geophys. Res. 84 (C6): 3173–3183.

Bibcode 1979JGR....84.3173W (http:/ / adsabs. harvard. edu/ abs/ 1979JGR. . . . 84. 3173W). doi:10.1029/JC084iC06p03173 (http:/ / dx. doi. org/ 10. 1029/ JC084iC06p03173).

• Kossin, J.P.; Schubert, W.H; Montgomery, M.T. (2000). "Unstable Interactions between a Hurricane's PrimaryEyewall and a Secondary Ring of Enhanced Vorticity". J. Atmos. Sci. 57 (24): 3893–3917. Bibcode2000JAtS...57.3893K (http:/ / adsabs. harvard. edu/ abs/ 2000JAtS. . . 57. 3893K). doi:10.1175/1520-0469(2001)058<3893:UIBAHS>2.0.CO;2 (http:/ / dx. doi. org/ 10. 1175/1520-0469(2001)058<3893:UIBAHS>2. 0. CO;2).

• Sitkowski, M.; Barnes, G.M. (2009). "Low-Level Thermodynamic, Kinematic, and Reflectivity Fields ofHurricane Guillermo (1997) during Rapid Intensification". Mon. Wea. Rev. 137 (2): 645–663. Bibcode2009MWRv..137..645S (http:/ / adsabs. harvard. edu/ abs/ 2009MWRv. . 137. . 645S). doi:10.1175/2008MWR2531.1 (http:/ / dx. doi. org/ 10. 1175/ 2008MWR2531. 1).

• Zhang, Qing-hong; Kuo, Ying-hwa; Chen, Shou-jun (2005). "Interaction between concentric eye-walls in supertyphoon Winnie (1997)". Quarterly Journal of the Royal Meteorological Society 131 (612): 3183–3204. Bibcode2005QJRMS.131.3183Z (http:/ / adsabs. harvard. edu/ abs/ 2005QJRMS. 131. 3183Z). doi: 10.1256/qj.04.33(http:/ / dx. doi. org/ 10. 1256/ qj. 04. 33).

• Emanuel, K (2003). "Tropical Cyclones". Annu Rev Earth Planet Sci 31 (1): 75. Bibcode 2003AREPS..31...75E(http:/ / adsabs. harvard. edu/ abs/ 2003AREPS. . 31. . . 75E). doi: 10.1146/annurev.earth.31.100901.141259(http:/ / dx. doi. org/ 10. 1146/ annurev. earth. 31. 100901. 141259).

• Oda, M.; Nakanishi, M.; Naito, G. (2006). "Interaction of an Asymmetric Double Vortex and Trochoidal Motionof a Tropical Cyclone with the Concentric Eyewall Structure". J. Atmos. Sci. 63 (3): 1069–1081. Bibcode2006JAtS...63.1069O (http:/ / adsabs. harvard. edu/ abs/ 2006JAtS. . . 63. 1069O). doi: 10.1175/JAS3670.1 (http:// dx. doi. org/ 10. 1175/ JAS3670. 1).

• Zhao, K.; Lee, W.-C.; Jou, B. J.-D. (2008). "Single Doppler radar observation of the concentric eyewall inTyphoon Saomai, 2006, near landfall". Geophys. Res. Lett. 35 (7): L07807. Bibcode 2008GeoRL..3507807Z(http:/ / adsabs. harvard. edu/ abs/ 2008GeoRL. . 3507807Z). doi: 10.1029/2007GL032773 (http:/ / dx. doi. org/10. 1029/ 2007GL032773).

• Kuo, H.C.; Schubert, W.H.; Tsai, C.L.; Kuo, Y.F. (2008). "Vortex Interactions and Barotropic Aspects ofConcentric Eyewall Formation". Mon. Wea. Rev. 136 (12): 5183–5198. Bibcode 2008MWRv..136.5183K (http:/ /adsabs. harvard. edu/ abs/ 2008MWRv. . 136. 5183K). doi: 10.1175/2008MWR2378.1 (http:/ / dx. doi. org/ 10.1175/ 2008MWR2378. 1).

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• Rozoff, C.M.; Kossin, J.P.; Schubert, W.H.; Mulero, P.J. (2009). "Internal Control of Hurricane IntensityVariability: The Dual Nature of Potential Vorticity Mixing". J. Atmos. Sci. 66: 133–147. Bibcode2009JAtS...66..133R (http:/ / adsabs. harvard. edu/ abs/ 2009JAtS. . . 66. . 133R). doi: 10.1175/2008JAS2717.1(http:/ / dx. doi. org/ 10. 1175/ 2008JAS2717. 1).

• Zhu, T.; Zhang, D.L.; Weng, F. (2004). "Numerical Simulation of Hurricane Bonnie (1998). Part I: EyewallEvolution and Intensity Changes". Mon. Wea. Rev. 132: 225–241. Bibcode 2004MWRv..132..225Z (http:/ /adsabs. harvard. edu/ abs/ 2004MWRv. . 132. . 225Z). doi:10.1175/1520-0493(2004)132<0225:NSOHBP>2.0.CO;2 (http:/ / dx. doi. org/ 10. 1175/1520-0493(2004)132<0225:NSOHBP>2. 0. CO;2).

• Nong, S.; Emanuel, K. (2003). "A numerical study of the genesis of concentric eyewalls in hurricanes". QuarterlyJournal of the Royal Meteorological Society 129 (595): 3323–3338. Bibcode 2003QJRMS.129.3323N (http:/ /adsabs. harvard. edu/ abs/ 2003QJRMS. 129. 3323N). doi: 10.1256/qj.01.132 (http:/ / dx. doi. org/ 10. 1256/ qj.01. 132).

• Kuo, H.C.; Lin, L.Y.; Chang, C.P.; Williams, R.T. (2004). "The Formation of Concentric Vorticity Structures inTyphoons". J. Atmos. Sci. 61 (22): 2722–2734. Bibcode 2004JAtS...61.2722K (http:/ / adsabs. harvard. edu/ abs/2004JAtS. . . 61. 2722K). doi: 10.1175/JAS3286.1 (http:/ / dx. doi. org/ 10. 1175/ JAS3286. 1).

• Terwey, W.D.; Montgomery, M.T. (2008). "Secondary eyewall formation in two idealized, full-physics modeledhurricanes". J. Geophys. Res. 113: D12112. Bibcode 2008JGRD..11312112T (http:/ / adsabs. harvard. edu/ abs/2008JGRD. . 11312112T). doi: 10.1029/2007JD008897 (http:/ / dx. doi. org/ 10. 1029/ 2007JD008897).

• Maclay, K.S.; DeMaria, M.; Vonder Haar, T.H. (2008). "Tropical Cyclone Inner-Core Kinetic Energy Evolution".Mon. Wea. Rev. 136 (12): 4882–4898. Bibcode 2008MWRv..136.4882M (http:/ / adsabs. harvard. edu/ abs/2008MWRv. . 136. 4882M). doi: 10.1175/2008MWR2268.1 (http:/ / dx. doi. org/ 10. 1175/ 2008MWR2268. 1).

Article Sources and Contributors 8

Article Sources and ContributorsEyewall replacement cycle  Source: http://en.wikipedia.org/w/index.php?oldid=520479418  Contributors: Anthony Appleyard, Cherkash, Chris the speller, Debresser, Earth100, Favonian,Headbomb, Hellbus, Hmains, Hurricanehink, Jason Rees, Jersey emt, Juliancolton, LilHelpa, Miller17CU94, Mortense, Müdigkeit, Nathan Johnson, Rjwilmsi, Soapthgr8, Victor Diovanni, Xeno,15 anonymous edits

Image Sources, Licenses and ContributorsFile:Project Stormfury crew.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Project_Stormfury_crew.jpg  License: Public Domain  Contributors: NOAAFile:TRMM Frances 30aug1021 utc lrg.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:TRMM_Frances_30aug1021_utc_lrg.jpg  License: Public Domain  Contributors: NASAimages produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC), NASA's Tropical Rainfall Measuring Mission.File:Typhoon Chanchu16-05-06.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Typhoon_Chanchu16-05-06.jpg  License: Public Domain  Contributors: Jeff Schmaltz, MODISRapid Response Team, Goddard Space Flight CenterFile:Hurricane profile.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Hurricane_profile.svg  License: Public Domain  Contributors: me, Jannev

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