436 MONTHLY WEATHER, REVIEW DECEMBER1956

HURRICANE SEASON OF 1956 GORDON E. DUNN,WALTER R. DAVIS, AND PAUL L. MOORE Weather Bureau Office, Mlarni, Fla.

TABLE1.-Damage and deaths from all tropical storms and dis- 1. GENERAL SUMMARY tnrbames of 1956 The 1956 hurricane seasonwas comparatively mild Type of storm Area from thestandpoint of stormfrequency. Only eight - ~___- tropical storms developed compared to an average during 4 La., Miss. 0 Tampico, Mex. thepast two decades of ten;four reached hurricane 18 French . 9 Puerto Rieo. intensitycompared to a normal of five duringrecent 0 Bahamas. 27 . years. In onlytwo of thepast 15 years have tropical 15 Mostly in La., Miss., Ala.. Fla. storms been so few and, by 1925 standards of detection HurricaneGreta- ...~~..~ 0 Mostly Fla. east coast.

3-5. ~.~ 1,899,201 Puerto1 Rico and other and classification, possibly only three storms would have islands in Antilles.

Tropical disturbance.. ~ ~ July 4-5-. ~ ~ ~ 503,000 0 Alabama. been designated astropical. Two storms reached the &uasi-tropicalstorm...~~ Oct. 15-16." 3,000,000 2 Florida. c___~

coastline of the United States, both in theGulf of Mexico. Total in United .. .~. -.~ ~. .. ~ ~ $30,007,605 The 1956 season was also mild from the standpoint of States. TotalAtlantic I..."-.-- ..... I$67,836,806 I il I tropical stormintensity. One of thestorms was of hurricane area. I I/ hurricane intensity for only a few hours, Flossy was of *Zero indicates no deathsreported. full hurricaneintensity nomore than 24 hours,and was asmuch extratropical as tropical storms and there was never any definite center or . during her lifet,ime. Indeed only Betsy appeared to have The temperature aloft over the surface Low remained as all the characteristics of the classical hurricane and even cold or colder than the surrounding air." The situation this storm did not increase in intensity andsize in accord- in the high troposphere was also markedly different from ance withstatistical expectancy. None of thefour that usuallyobserved duringhurricane formation. At hurricanes of 1956 couldbe classified as severe (120 to 250 mb.,at 0300 GMT on the12th, an intense cyclonic 150 knots sustained wind). circulation was centered southeast of Fort Worth and at Tracks of the tropical stormsof 1956 are shown in figure 0300 GMT on the 14th this center had moved almost over 1 and death and damage data are tabulated in table 1. the tropical storm in Louisiana. 2. INDIVIDUAL STORMS The highest wind reported ashore was 55 m. p. h. from the east at Grand Isle, at 0715 CST on the 13th. A boat UnnamedTropical Storm, June 1l-ld."This was the 5 miles sout'h of Pilottown,La., reported gusts to 60 second tropical storm to occur in June in 10 years. On m. p. h. from the south-southeast. The lowest observed June 9, a fracture occurred in the polar trough lying just pressurewas 29.66 inches at MoissantAirport, New off theAtlantic coast, and t'he southernsection began Orleans,and at McComb,Miss. The highest measured moving westward across Florida into the tide was 4.7 feet above mean level at Biloxi, Miss. whiletEe northern section continued eastward over the The heaviest rainfallwas within 100 miles of and to the western Atlantic. The westward moving southern section east of t'he storm track and decreased from 6.13 inches at apparently induced an easterly wave which moved across Grand Isle, La., to 5.60 inches at Monticello, Miss., 3.17 t8heextreme western , western , southern inches at Jackson, Miss., and 1.60 inches at Greenwood, Florida,and the Yucatan Peninsula, and on the12th Miss. The benefit to crops from these rains, which ended formed a depression in the Bay of under the a drought at least temporarily, exceeded property losses mid-tropospheric trough. The disturbance moved north- from wind and water on the coast. ward,acquiring tropical storm intensity and the center Four persons were drowned, three of them when a tug crossed theLouisiana coast a short, distance west of sank off the Mississippi coastand the other, a truck Grand Isle during the late forenoon of the 13th. Accord- driver, when his truck skidded on the bridge over Lake ing to the report from t'he hurricane forecast center at New Orleans, "The storm had both tropical and extra- Pontchartrairl and plunged into the lake. The bridge was tropical characteristics.Rainfall was tropical in nature damaged by the truck but moreseriously by a loose barge. but neverformed inbands characteristic of tropical The total damage to the bridge was estimated at $12,000.

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FIGURE1.-Tracks of hurricanes and tropical storms that occurred during 1956 in the North Atlantic .

Tides generally ranged from 1 to 4 feet above normal sion intensified to storm intensity on the afternoon of the along the Louisiana and Mississippi coasts. The Freeport 25th. Sulphur Co. suffered some damage to their sulphur mines On the morningof the 26th, Navyreconnaissance located near the coast' south of Houma, La., where the tide was the center with lowest pressure 991 mb. (29.26 in.) and 4.5 feetabove mean sea level. Minordamage to the found maximum winds of 50 knots in the northern semi- beaches, small boats, and piers occurred along the Missis- circle. Early that evening the center moved inland south sippi coast in places where tides were said to have reached of Tampico, Mexico where a maximum wind of 70 knots as much as 5 feet above mean sea level. The total dam- (81 m. p. 11.) was reportedwith lowestpressure 29.60 age from this storm is estimated at $50,000. inches. It is thought that winds of hurricane force existed HurricaneAnna, July 25-26.-The easterlywave in only for about three hours as the center approached and which Anna developed passed through the crossed the coastline. on July 20 and continued westward through the Caribbean. Many houses in the poorer sections of Tampico were Instability of the wave began to increaseon the 23d as the blown down and some roofs of thebetter homeswere wave, extending on the surface from central Cuba to Pan- blown off. Although only 2.5 inches of rain were reported, ama, passed under a very well developed anticyclone in downtown streets in Tampico were flooded. There were themiddle and upper troposphere. A weakcirculation no reports of deaths or injuries. Damage has been esti- may have developed as it moved over the Yucatan Pen- mated at around $50,000. insula on the night of the 24th but all surface winds were , August 9-19.-The general circulation under 20 m.p. h. Intensificationwas steady after the over the Atlantic during most' of the hurricane season of center passed into the Bay of Campechr and the depres- 1956 and its possible relationship to the mildhurricane

Unauthenticated | Downloaded 09/23/21 06:07 PM UTC 438 WEATHERMONTHLY REVIEW DECEMBER1956 activity will be discussed later.A temporary break in through the central Lesser Antilles about midday August the prevailing circulation pat'tern occurred earlyin August 11. It crossed over the island of Marie Galante and be- as the Azores-Bermuda anticyclone moved northeastward tween Isle des Saintes and tlle extreme south portion of for a period of about a week and intensified while a trough BasseTerre, . Reports indicate 18 lives lost extended through western . Similar patterns have and severedamage. On Guadeloupe, 1,000 dwellings been noted previously [I] as antecedent to hurricane for- were extensively damaged, all communications disrupted, mation.Apparently the injection of cold airaloft and and 50 to 60 percent of the banana, breadfruit, coconut, cyclonic vorticityinto the Tropics by a meridionally- and papaya trees destroyed,a serious blow to the economy extensive trough encourages the transformation of st,able of theisland. The banana crop loss wasestimated at waves in the easterlies, and even in the intertropical con- $3.5 million and preliminary estimates give$10 million for vergence zone,into unstable waves andeventually into the total damage figure. Winds were estimated at 100 to storm circulations. Around August 9, when the develop- 120 m. p. h. on Guadeloupe and the lowest) pressure was ment of Betsy wasfirst suspected, the ant'icyclone had 991 mb. reached maximumintensity and immediately beganto After moving through the Leeward Islands, the hurri- subside and to return to its previous position south of its c'ane began a more northwesterly course, passing about30 normal location. miles south of St. Croix, , and reaching the Lack of reports in the eastern Atlantic, makes it'impos- southeastern tip of Puert'o Rico in the early morning of sible to arrive at a detailed analysis for the period preced- August 12. Priorto reaching the storm ing the first indications of this storm but there was some displayed a small but apparently real oscillatory motion evidence of an easterly wave near longitude 33' W. on about the mean track with an amplitude of a little less August 6. Extrapolation at' a normal rate of movement than )i degree and a period on the orderof one day. The would have brought it to the vicinity of 50' W. on the oscillation was sufficient'ly definit'e that, some forecast use 9th. On that date the following report was received from could be made of it, on an ext'rapolation basis. Following the M/T Marisa: "At 1218 GMT passed through t,rough of the turn to a more northwesterly direction, thisoscillation tropical storm inposition 14.05' N., 55.25' W. At 1200 was not' present or was obscured. GMT 1008 mb., winds force 10, very high wild sea, heavy A hurricane watch had been ordered for Puerto Rico squalls." It was not possible t'o fit this report into anv and the Virgin Islands on t'he evening of August 10. As logical analysisand consequently effortswere made to the hurricane continued to move toward Puerto Rico, the verify the ship's position. At 1730 GMT a corrected posi- watch was changed to hurricane warningson the afternoon tion of 14.05' N., 49.05' W. was obtained. This was only of August 11. The eye of the storm crossed Puerto Rico a short distance from the routine Gull Papareconnaissance between 1200 and 1530 GMT, August 12, on an erratic track but the developing st80rm wast'oo small to alert tlle coarse 121 between nort'hwest and west'-nort,hwestat about reconnaissance observer and there was no diversion from 17 m. p.h., emerging on the north coast near Camuy with the scheduled track. onlyslight and temporary weakening of its circulation. A special reconnaisance flight was made on August 10, According to reports, all of Puerto Rico, except t'he south- but confirmation of st,ormdevelopment wasreceived westernportion which was protected by the mountain through surface ship report's before the plane reached the backbone of the island, experienced winds of 75 m. p. h. area. The MIS Sagoland at 1200 GMT reported: ((Lat. orhigher in gusts.Maximum sustained winds at San 14.35' N., Long. 54.10' W., at'0400 GMT, wind 035 degrees Juan were 73 m. p. h., with gusts t'o 92 m. p. h. Rainfall increasing force5, barometer 1008 mb. At' 0930 GMT tot'alled 3.19 inches. Ramey Air ForceBase, on tho northeast force 11/12, barometer 1004, violent sea, heavy northeastern tip of the island, recorded wind gusts to 115 rain, no visibility. At 1200 GMT wind east force 6, barom- m. p. 11. Nine deaths were reported in Puerto Rico and eter 1009, heavyseas, rain, decreasing sea." The 1200 t'he property damage totalled $25,500,000 or more. GMT observationsfrom the SS MormacLark and SS HurricaneBetsy continued at aspeed of about 17 Willemstadt on t.he outskirts of the storm, were also help- m. p. h. tonear Turks Island early on August 13 and,with ful in thelocation of thestorm and evaluation of its some acceleration, reached the vicinity of San Salvador in intensity. about 2000 EST on that date. Winds at San The first advisory was issued at 1100 EST, August 10, Salvador reached 132 m. p. 11. in gusts. Sustained winds at which time a hurricane watc,hwas advised for the TJee- were 100 m.p. 11. ormore. Approximately 5 inches of ward and Windward Islands from Antigua to . rain fell in 5 hours. Several houses were demolished and When reconnaissance aircraft reached the storm later in most of the churches,which are generally better con- the day,it was found to bea very small hurricane but with structed, lost their roofs. winds of 120 m. p. h. near the center and centralpressure Aircraftreconnaissance on August 13 had shown a 979 mb. The eyewas defined by a verytightly closed slightincrease in size of the storm but little change in pattern on the radar as only 10 miles in diameter. centralpressure or maximum winds. Gale winds were Thehurricane moved on a west-northwest course at reported as extending 125 miles north and 60 miles south about 17 m. p, h. during t8he next 24 hours and passed of thecenter. Lack of important increase in size or

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intensitywas compatible with the fact that turbulence day fact'or. At 1700 EST, on the 13th, it was decided that and rain in all quadrants were predominantly light with with the rate of advance and the direction and speed of only intermittentbursts of heavyrain and moderat,e movement indicated by the Riehl-Haggard [3] technique, turbulence. On the14th, central pressure was reported which gave excellent results on the whole with this storm, as960 mb., the eyewas 12 miles indiamet'er and well squalliness could develop on the Florida southeast coast formed, and associated clouds extended 250 miles nort'h on the forenoon of August 14. If hurricane warnings were and 200 miles to the east. delayed untilthe next morning, and the forecast track On August 14 and 15, Betsy began recurvature with verified, insufficient timewould remain for adequate sharp deceleration inforward movement. Bythe 16th preparat'ions.Consequently, hurricane warnings were it was moving toward the northeast and had increased its issued for a portion of the Florida east coast. The under- forwardspeed toabout 20 m.p. h. Between the 13th) lying reasons for the action, and thedegree of uncertainty when thestorm was nearTurks Island, and the 16th, at'tached to a hurricane forecastfor such a period of time, when a dropsonde was released in the eye near 30' N., were expressed inthe public advisory. By the morning 75O W., temperatures in the eye between the surface and of August 14 stronger evidence in favor of a northward 700 mb. fell about 2' C. The normal sea-surface temper- turn was appearing,and later in the day all hurricane ature difference between these areas is less than 1' and, warningswere lowered. However,there remained an- while some anomaly may haveexisted, it' seems likelythat other 24 hours of slow movement during the recurvature the cooling was an indication of the beginning, even at process before all threat to t'he United States coast had thistime, of some otherfactors int'erfering with the definitely passed. efficiency of the storm engine. By the 17th, a dropsonde At 500 mb., during the early history of Betsy, a trough in the eye showed that t'he c,ooling, by another loto 3' C., extended from Newfoundlandto near Bermuda. The extended upward to almost the 500-mb. level. Maximum southernportion of thistrough tended to fill asBetsy winds began to decrease on the 16th and by late August moved past,and heights in the area of an anticyclone 17th had dropped to 80 m. p. 11. Reconnaissance at this alongthe southeastern United States coast had been time report'ed the eye was becoming poorlydefined as the rising for some t3imewhen the storm reached the area of hurricane moved northeastward at about 23 m. p. h. past TurksIsland onAugust 13. This,with other factors, the latitude of Nantucket. The last advisory was issued createdsome doubt as to whether recurvature could on the morning of August 18 as t'he storm assumed more occur east of Florida.The long-wave patternat this extratropicalcharacteristics. It moved dueeast on tbt: time was becoming poorly defined and of small amplitude, 19th and 20th, graduallylosing its identit>-. withindications that atrough should develop in the The tracking and forecasting of hurricane Betsy was Great Lakes , permitting the High along the south- aided by the availability of more information in the form eastern coast to persist and hamper recurvature. It was of air-borne and land-based radar observat'ions and upper notuntil t,he 14ththat developments, including the air soundings than in previous years. The storm succes- weakening of the High over t'he southeastern coast, began sively came within range of radar at' San Juan[2], the Air to favor the nort'hward turn. Force missile range stations in the Bahamas, andt'he Navy Theaccepted movement-forecast techniques were HurricaneCentral at Miami.The AN/CPS-9 radarat' applied and were found useful to varying degrees. None theNavy Hurricane Central, Miami, established what were without failures at some stage, particularly during possibly may be a record when hurricane Betsy was off recurvature.Three 24-hourforecasts obtained by the the Florida coast on the 14t'h. The center of Betsy was Riehl-Haggard technique were within 17 miles, which is initially detected by this radar at a range of 293 nautical as close asthe center can usually belocated at sea. miles and presented a perfect scope picture for t'he next However,passage of the storm through the network of 26 hours until she was lost at 269 naut'ical miles. upper-air stationsat Air Forcemissile bases and on islands Aircraft reconnaissance by the Air Force and Navywas to the south permitted the collection of data which may upto its usualhigh st)andards. Despite all this,Betsy prove helpful in analyzing some of these deficiencies in was not without forecasting problems. The most difficult ourpresent knowledge of hurricanebehavior. This is problem, as it usually is, was the recurvature. From the especially true of the upper troposphere, for whichwe have time of inceptionuntil August 13, themovement was previously had severely limited data. consistentand could beforecast with a high degree of There were at least 27 deaths connected with Betsy, confidence. However,on thatdate the center was ap- andtotal damage in monetaryterms, including an proaching anarea where recurvatureappeared to be a estimate of $380,000 inthe Bahamas and a few other likely possibility on the basis of climatology, and a slight islands, appears to be around $35,880,000. possibility on the basis of the prevailing circulation. From Tropical Storm Carla, September 5-ii.--The first in- thestandpoint of publicwarnings, the problem was dication of Carla appeared on September 5 when a weak further complicated by the relatively rapid movement of circulationshowed up in an easterly wave which was 18 m. p. h. (during certain short periods on this date it moving into the southeastern Bahamas. During the next appeared to move as fast as 25 m. p. h.) and the time-of- several days it moved on a parabolic course and on the

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7t,h recurved nort,heastward with some deepening and the pressure wm the same andmasximum winds were50 knot8s. area of strong winds expanded to cover an area 300 t80 Thecenter moved inland around noon nearTuxpan, 400 miles in diameter. Mexico with lowest pressure 1002 mb. and highest, wind A strong southeastward out'breakof polar airwas taking 30 knots. place inthe eastern and central United States and the The New Orleans forecast center reported that heavy accompanying cold front passed off the east coast during rains in Mexico caused a landslide in which 13 persons in the morning of the 7th. On the 8th interaction between a bus were killed and these deaths were attributed to the the High with central pressure 1034 mb. over the Lakes storm. Some flooding occurred from the heavy rains, but Region and the tropical Low off the southeastern United damage is believed t,o have beenslight. A later news States coast was causing strong northeast winds from t'he dispatchsaid, "The death toll from after-effects of centralFlorida coast northeastward along and off the Mexico's short lived HurricaneDora rose to 27 today Georgia andCarolina coasts. Gales spread to t,he New withreports of 7 personsdrowned inthe overflowing England coast as the Low moved to a posit'ion near Lat. Paclluapan River near San And& Tuxtla." 32.5" N., Long. 70" W. by the morning of the 9th. Re- At 200 mb.the st'orm remained south of, and about connaissance aircraft on the morning of the 9th locat'ed an midwaybetween, a. Highcentered over Texas and a ill-defined cent.er but reported no eye existed and no spiral troughover the east'ern Gulf-not avery favorable bands were in evidence. Highest surface winds near the location for rapid intensification. center were estimated at 30 knots.However, 40 t,o50 TropicnlStorm Ethel, September 11-lS.-At1330 EST m. p.h. windswere found extending 200 miles tothe Sept,ember 11, a weak circulation was noted over Great west and northwest and 40 m. p. h. winds some distance Emma Island in the Bahamas, about 100 miles sout,h of tothe east, andsouth. During the period of greatest aquasi-st'ationary front. During tlhe next 24 hours t8he intensity,the dorm was probablynot a true t>ropical tropical depression lnoved north-northeastward and grad- storm. It had definitely takenon extratropical char- ually intensified. On the afternoon of the 12th) research acteristicsby the forenoon of the 10th and only three aircraft reconnaissance enteredthe storm and found a advisories were issued. well-developed eyeabout 20 miles in diameter and entirely On the morning of September 5,when t'he weak easterly surroundedby a typical wall cloudextending upward waveextended nort,heast-southwest through the south- about 30,000 feet.A maximum wind of 66 kn0t.s was western Bahamas, a weak trough or shearline existed in encountered while enteringthe eye over a distance of this area at all levels to 500 mb., with a deep Low at 300 some3 miles in t'he northeasternquadrant. Thirty- mb., about 700 miles to the northeast near Lat. 26.5ON.) knot winds extended outward 30 to 100 miles in all direc- Long. 62.5" W. During the next two days t'his 200-mb. tions but no hurricanewinds were found in anyother Low seemed to split, with one section moving off to the quadrant. northeastand the other drifting southwestward over By late on the13th) the st'orm had assumed extra- Cubainto the northwestern Caribbean and over the t'ropical characterist'icsand lost intensity. It is thought Yucata,nPeninsula by the evening of the8th. At t,hat the storm may have developed strongly for a short aboutthis same time, the polar trough at themid- t'ime as a new source of energy in the form of cold air troposphere was moving off the coast of the southeastern entered the system. Since development took place under States and deepening, and by the morning of the loth, a broad polar trough, even this much intensificat,ion was Carla, now almost entirely surrounded bycool air at lower surprising. If the research plane had not flown into the levels, was pulled into the trough and carried rapidly out storm on the 12t,h, no advisories would have been issued over the Atlantic to the northeast. and it would not have been listed a.s a tropical storm. Thus it may be seen that during t8heformative stage of , September WlSO."The origin of this Carla, it was never in a favorable locationwit'h respect to hurricane-the only one to reach the coast of the United t,he 200-mb. high pressure cell to augment deepening. Statesin 1956-is rather obscure. Hurricanesqualls TropicalStorm Dora, September 1O-l,%'.-A t,ropical were reported in the Pacific south of Guatemala on the stormformed during the afternoon of September 11 in 20th, and the initial impulse may have moved northward t,he southwestern Gulf of Mexico in a depression that had fromthere or fromthe Caribbean. The first well- been driftingwestward. Navy reconnaissance during developedcirculation was noted over the Yucatan the previous afternoon found a rather large area in the Peninsula at 1330 EST on the 21st, passing into the Gulf Bay of Campechewith scattered squalls. The lowest, of Mexico near Mericla. According to the report of the pressure was 1010 mb. and the maximum wind 35 kn0t.s. hurricane Eorecast center at New Orleans, the circulat#ion On the 1Ith, aircraft reconnaissance found the lowest intensified gradually while movingnorthward over the pressure to be 1004 mb. and the maximum wind 65 knots. Gulf and reached st,orm intensity on the afternoon of the This storm has not beenclassified as a hurricane since the 22d. After this time the size of the storm increased con- 65-knotwind was an estimate and not a measurement,, siderably butthe pressure gradient around the center and it is not believed that the required pressure gradient intensified only slowly. The tropicalstorm reached for thisspeed existed. The nextmorning the minimum hurricane force near or somewhat before noon on the 23d

Unauthenticated | Downloaded 09/23/21 06:07 PM UTC DECEMRER1956 MONTHLYREVIEW WEATHER 441 when the center was ahout. 125 miles off t,he sout~heastern relative calm nearthe location of lowest pressure were Louisiana coast. also observed. Duringthe afternoon the hurricane t'urned rat,her The Woods HoleOceanographic Institution research sharplyt'oward the easbnortheast, crossing the Missis- vessel Crawford, on a weather mission in the Caribbean, sippi delta a little northof Burrwood near Pilott'own early was very near the circulation center during the afternoon on the24th. Here it seemsto havereached maximum andevening of the30th and encountered 25 m.p. h. intensity with highest wind at Burrwood 84 m. p. h. and southeasterly winds and a minimum pressure near 1005 lowest pressure 29.03 inches. An oil rig a little west of mb. (29.68 in.). Aradiosonde observation taken by the Grande Isle reported a maximum wind of 83 m. p. 11. and Crawford shortly after their winds shifted from the south- gusts to 95. The New Orleans forecast cent,er attributes east to northwest indicated theLowwas definitely cold-core the turn to the east-northeast. to "the central core of thc as opposed to the warm core associated with hurricanes. hurricane building upward and reaching into the west.er- The Lowcontinued northward at about 15 m. p. h. lies." This change in direction was also indicated by the witha gradual intensification and by November 1 the Riehl-Haggardforecasting technique. The center passed lowest, pressurehad decreased to 998 mb. (29.47 in.). a lit'tle south of Pensucola, Bla., during the aft'ernoon and Winds of 30 to 40 m. p. h. were reported over a large area her about over Fort) Walton. The storm became extra- surroundingthe center, but gentle variable winds and tropical shortly after the center passed out of Florida but calms still covered an extensive area near the center. it moved northeastward inside the coastline as an ener- A large high pressure system, which had st,agnated some getic storm until it. passed out to sea near the Virginia distance off the middle Atlantic coast during the last few Capes. days of October,blocked further northward movement As far as known, no hurricane winds were reported at so that during the night of November 1, the storm looped anyFlorida point, although windswere nearhurricane and t'ook a southeastward course with a somewhat slower force eastward along thecoast to Panama City. The speed. It was during this period, asshown by datareceived lowest pressure reported during the stormwas 28.93 inches from planes of the National Hurricane Research Project, at the Pensacola Naval Air Station. The highest storm that Greta assumed tropical storm characteristics with a tide was 7.4 feetm. s. 1. at LagunaBeach, Fla. Some minimum pressure of 992 mb. (29.29 in.). higher values were reported along the eastern side of the It is believed that Gret'areached hurricane intensity Mississippi deltabut have not been verified. Tides on the afternoon of November 3 or early on the 4th, and flooded portions of Norfolk,Va., and water st'ood 2.5 continued to intensify until November 5 when winds in feet deep in several of the principal street's. Beach erosion excess of 100 m. p.h. and a minimum pressure of 970 occurred as far north as Delaware. mb. (28.64 in.) were reported by reconnaissance aircraft. Theheaviest rainfall reported was 16.70 inches at Duringthis period the forward motion becameeast- GoldenMeadow, La., and 16.30 inches at Gulf Shores, northeast at 20-25 m. p. 11. OnNovember 6 and 7 the Ala. The rainfallintensity decreased graduallyas the stormcontinued east-northeastward atan accelerated storm moved northeastward but 1 to 3 inches fell as far speed,gradually assuming extratropicalcharacteristics nort'has Virginia. Threetornadoes were report'ed in dueto much colder ocean temperaturesand an influx advance of thestorm in northwest.ern Florida and an- of cold air. otherat Hilton Head Island near Savannah, Ga., but Inmany ways Greta wasa mostunusual tropical each caused only minor damage. cyclone. For a long period it had all the characteristics Tot'aldamage in the States of Louisiana,Florida, of a cold Low frommiddle latitudes. There is some Alabama,and Mississippi was $24,774,000 of which evidence t'hat it mayhave been similar to the Kona $15,204,000 was to crops. Damage in other States such as storms of t8hePacific both in origin and size. The rapid Georgia,the Carolinas, and Virginia was $100,000 or intensificationto hurricane force with a southeastward less and was greatly outweighed by t,he beneficial rains movement has been rarelyobserved. Middle-latitude which relieved droughtconditions. Deaths, mainly conditions at this time indicate an energy transfer from fromplane and automobile accidents at'tribut'ed to t'he upstream may have occurred. storm,totalled 15. Warningsthroughout, the st'orm The circulation formed by the hurricane and the large were timely and accurate. anticyclone to the north covered a tremendous expanse of The origin of Flossy has been discussed by Hawkins the and the long fetchof the strong winds [4] andits transformation to an extratropical st'orm by set up much larger waves and swells than indicated by Richter and DiLoreto [5]. thenormal wind-sea-swell relationships.On the south Hurricane Greta, October 30-November 6."A depression, which is believed to have had its origin along the inter- Atlantic coast, damage was worst along the Jacksonville tropicalconvergence zone over the southern Caribbean, beaches where the water is relatively deep a short distance was first noted southeast of on October 30 when offshore. Damage in Puerto Rico from swells at least 20 a Navy reconnaissance flight observed 35-m. p. h. south- feet high was heavy. Sta. Lucia, B. W. I., reported 20- easterly winds. Numerousshowers and a large area of foot swells from the west-northwest and some as much as

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25 feethigh. The suffered severely Tropical depression, September 13.-A vigorous depres- with 80 percent of theport installations destroyed at, sion passed t'hrough the CapeVerdes on the 13th, attended Basse Terre, Guadeloupe. Damage, almost ent'irely from bysqualls. Maximum winds are unknown. The de- sea action, was as follows: pression was completely damped out before reaching the

Jacksonville beaches, Florida ______~__- $1, 170, 605 Antilles . Elsewherealong southeastern U. S. Tropicaldepression, October 9.-Some 1,300 miles east coast_.______-"--^^^------510,000 of Puert'o Rico on this dat)e, ships reported squallsof 40 to

Puerto Rice__." _____ ~~~~~~~~ _._____1, 194, 701 45 m. p. h. and there was evidence of at least a quasi- Virgin Islands___- ~ - ~ ~ - - - -.------.- ~ ~ 45, 000 circulation It was completely dampedout within 24 Dominica__. ~ ~ ~ ~ ~ ~ ~ - ~ - -.- 291,500 hours. Sta. Lucia and Pigeon Island- ~ ~ ~ ~ - ~ ~ ~ ~ 68, 000

French West Indies" ------~ - ~ - ~ ~ ~ ~ - ~ 200, 000 Tropical depression, October 10-1W.-Probably develop-

Other Caribbean Islands- - -.~ ~ ~ ~ - ~ - -.- 100,000 ing from the same easterly wave but farther tobhe north, ~~ a tropical depression formed on October 10 and moved in Total ______~_~~~~~~~~__ $3, 579,806 ageneral northerlydirection for several days wit'hout There was one death in Puerto Rico by drowning of the furtherdevelopment. It, was not the same depression occupant of an exposed house who did not heed a warning noted on the 9th. to evacuate. Quasi-tropical Low,October 13"9.-This Low formed as a wave on a dissipating polar front northof on 3. OTHER TROPICAL OR QUASI-TROFICAL DISTURBANCES the 12th and moved west-northwestward to t'he extreme southeast'ern Florida coast south of Miami on the 15th, An unusualnumber of t'ropical disturbances which when it turnednort'h and north-northeastward passing failed to acquire winds of as strong as 40 m. p. 11. were over the North Carolina Capes west of Cape Hatteras. notedthis year. If entirelytropical in nature, most' of Rainfall was excessive in portions of Florida ranging from them can be classified as tropicaldepressions which may be 6 to 20 inches over a 50-mile wide belt from the nort'heast- defined asweak cyclonic disturbances of t'ropical origin erncorner of Lake Okeechobee to Jacksonville.This and with winds less than 40 m. p. h. Since some of these storm never became wholly tropical, and maximum winds tropical and quasi-tropical disturbances were of some im- and most of the precipit'ation occurredwell in advance of portance, a partial list follows: the low pressurecenter. Highest winds reported were Tropical depression,June 17-18.-A tropical depression, gusts of 60 to 65 m. p. h. and probably some sustained which briefly caused squalls up t'o 40 m. p. h.,was located winds of near 60 m. p. 11. at sea. Damage from flooding 500 miles east of the south Florida coast on June 17-18. in Florida, particularly around Kissimmee, totaled about Little evidence of it could be found after 1330 EST on the $3,000,000. Two persons were drowned in the surf during 18th. The lack of deep east'erlies north of t'he area, and t'he storm. troughy conditions over the disturbance at 200 mb. were 4. POSSIBLE CAUSES OF THECOMPARATIVELY considered unfavorable for development. MILD HURRICANE SEASON Tropicaldepression, July 4-8.-A completealthough very weak circulat'ion was noted at 1930 EST on July 4, One of t'he currently accepted requirement's for hurri- at Lat. 26.2O N., Long. 86.2' W., developing under a cold ('anc formation is a warm sea surface with temperature troughin t,he mid-troposphere. It movednorth-north- 80' F. or higher. Rich1 [6], however, has failed to find westward and northwestward on t'he 6t'h causing gust,s of useful correlationsbetween sea surface temperature 38 knots at Panama City and moved inland near Pensa- anomaliesand hurricane formation on amonthly or cola late on the 6th where the lowestbaromct'er noted ycarlybasis. At the sametime when thetime scale of was1011 mb.Whatley, Ala., reported 14.22 inches of correlation was increased t'o 5 yearsand more, some rain during the storm and 10.85 inches in 24 hours. improvement in the correlations was noted. Property damage was estimated at $400,000 from the On the other hand, Fisher [7] has found some evidence, heavy rains,plus $IOO,OOO cropand $3,000 livestock althoughnot conclusive, that,hurricanes tend t,o form damage. Many highwayand railroad bridges were near relatively warm ocean areas, that they tend to follow washed out and erosion of roads was extensive. tracks along t'he areas of warmest water, and that' they Tropical depression, August %-September6.-On August tent1 to weaken when theymove over pronouncedly 28 anunusually strong wave on theintertropical con- colder water. Some of t'heexamples cited by Fisher vergence zone began approaching the Cape Verde Islands appear to require high a degreeof subjective interpret'ation. and soon developedconsiderable intensity. St,ation SAL At the time of preparation of this article, thesea surface in theCape Verdeson the31st observed a barometer temperature anomaliesfor thishurricane season have reading of 1004 mb.Several ships in the area report'ed been analyzed for June, July, and August. During these winds of 35 to 40 knot>s.After leaving the Cape Verde months, sea surface temperatures appear t,o have been near area,the storm apparently gradually decreasedin in- or above normal everywherein the western and central tensityand finallydissipated nort'heast of t'he Leeward portions of the tropical At'lantic. Samplings for October Islands on the 6th. indicatenegative departures from normal [8]. Since sea

Unauthenticated | Downloaded 09/23/21 06:07 PM UTC DECEMBER1956 MONTHLY WEATHER REVIEW 443 surfacetemperature anomalies are probably a result of and that strong and deep subtropical easterlies were prev- abnormalities in the general circulation, it may be diffi- alent, t’his never seemed to be t,he case in the area where cult to separate theeffect of each in inhibiting orencourag- t,he depressions formed. Almost invariably these disturb- ing hurricane incidence. ancesformed undera relatively cold trough which we Another generally accepted requirement for hurricane normally consider an unfavorable location for hurricane development is the existence of some preexisting disturb- development. ance. Easterly waves reaching the eastern Antilles appear Hawkins [8] has pointed out that t,he mean circulation t’o have been about normal in number but perhaps weakerpatt’ern at 700 mb. during October 1956was similar to than usd. Thenumber of tropicaldepressions which patterns that Ballenzweig [9] found t’o be gene,rally favor- failed to develop intotropical storms was greater than able t’o hurricane development’ and subsequent incidence normaland this was particularlytrue in the western inthe Florida area. To accountfor the single quasi- tropical Atlantic t,hroughout t,he season and in the Cape tropical Low this October, Hawkins noted that a sampling Verde region in August and September. of sea surface temperatures over the Gulf, Caribbean, and Thus, largely by theprocess of elimination we are forced tropicalAtlantic indicated below normal values for the to turn to the general circulation in an effort t,o find the month, but he made no attempt to relate this anomalyt,o causes of thesubnormal hurricane season. The require- t’he atmospheric circulation of preceding months. ments of an essentially barotropic atmosphere in the low and middle troposphere and a deep easterly current are REFERENCES provided by certain circulation types. In June the sub- 1. J. Namias and C. R. Dunn, “The Weather andCircula- tropical ridge was located considerably north of its normal tion of August1955”Including the Climatological positionin theeast>ern United States and most of the Backgroundfor Hurricanes Connie and Diane,” Atlantic. Namias and Dunn [I] have indicated that this k!onthly Weather Review, vol. 83, No. 8, Aug. 1955, is favorable for tropical storm activit,y. To a lesser extent pp. 163-170. this same situation obtained in October and in both these 2. R. J. Grace, “Betsy’s Roving Eye,” Monthly Weather months tropical st’orm activity was normal or above. Review, vol. 84, No. 8, Aug. 1956, pp. 311-312. However,from early July into early September, the 3. H. Riehl, W. H. Haggard, and R.W. Sanborn, “On the circulationover t’he Atlantic Ocean in 1956 differed Prediction of %-Hour Hurricane Motion,’’ Journal radically from that of 1954 and 1955 and indeed many of of Meteorology, vol. 13, No. 5, Oct. 1956, pp. 415-420. tlhe years since theearly 1930’s. In 1954 and 1955 t’he 4. H. F. Hawkins, Jr., “The Weat’her and Circulation of westerlies were far north of their normal position and dur- September1956”Including a Discussion of Hurri- ing the greater part of 1956 were south of their average caneFlossy and September’s Typhoon Tracks,” position.dccording t’o Jerome Namias,” fast westerlies Monthly U’eather Review, vol. 84, No. 9, Sept. 1956, (the speed of the westerlies is usually above normal when pp. 336-342. theirprincipal axis is comparativelyfar south) inhibit 5. D. A. Richter and E. A. DiLoreto, “The Transforma- the deployment int’o the Tropics of deep polar air masses tion of Hurricane Flossy into an Extratropical Cy- which must,be prolonged andpersistent to provide a clone, September 25-29, 1956,” MonthlyWeather favorableupper-air climate for hurricane genesis. Un- Review, vol. 84, No. 9, Scpt. 1956, pp. 343-352. usually low-latitude west,erlies in the Atlantic,cont.ra.ct, t’he 6. H. Rielll,“Sea Surface Ternperat*ure Anomalies and area of deep easterlies. This same circulation type tends Hurricanes,” Bulletin qf the American Meteorological to shunt any hurricanes which do form away from the Society, vol. 37, No. 8, Oct. 1956, pp. 413-417. Kort’h Atlantic and Middle At,lantic coasts. At the same 7. E. L. Fisher, “Hurricanes and the Sea SurfaceTem- t8irne, eventhough the overall hurricane frequency de- perat,ureField,” Depart’ment of Meteorology and creases, hurricane activity increases somewhat locally over Oceanography,New York University, Technical the Gulf of Mexico, Florida, and the Caribbean. Paper No. 1 on contrac,t’ wit,hU. S. Weather Bureau During most of September, the position of the strongest Nat,ional Hurricane Research Project, July 1956. westerlies was about normal and therewere a considerable 8. H. F. Hawkins, Jr., “The Weat)her and Circulation of number of incipienttropical disturbances (depressions) October 1956”Including a Discussion of the Rela- which failed to intensify mat,erially. In other words, there t,ionship of Mean 700-mb. Height Anomalies to Sea was some persistent inhibiting factor which has not yet Level Flow,” Monthly Weather Review, vol. 84, No. been identified. It may have been subnormal sea tempera- 10, Oct. 1956, pp. 363-370. tures in some areas, unfavorable upper-troposphere condi- 9. E. ?\I.Ballenzweig, Seasonal Variations inthe Fre- tions, or some facet of the general circulat]ion. Alt8hough quency of North Atlantic, Tropical Cyclones Related Hawkins [4] found that circulationover the Atlant’icin t,o theGeneral Circulation, unpublished report of September resembled t’hat of 1955 to a considerable extent’ U. S. Weather Bureau, Extended Forecast. Section,

‘Personal communication to thc authors. Sept’. 1956.

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