Tropical
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Monthly Global Tropical Cyclone Summary February 2006 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY FEBRUARY, 2006 (For general comments about the nature of these summaries, as well as information on how to download the tabular cyclone track files, see the Author's Note at the end of this summary.) ************************************************************************* FEBRUARY HIGHLIGHTS --> Another intense tropical cyclone roams Southwest Indian waters --> One hurricane in South Pacific east of Dateline --> Couple of minor tropical cyclones form off northern Australia --> Apparent tropical storm forms off coast of Brazil ************************************************************************* ********** EXTRA FEATURE ********** A COMPARISON BETWEEN THE AUSTRALIAN CYCLONE SEVERITY SCALE AND THE SAFFIR/SIMPSON SCALE ---------------------------------------------------------- Both the U. S. National Weather Service and Australia's Bureau of Meteorology (BoM) employ a 5-point scale by which to alert the public of the general effects which can be expected from tropical cyclones of varying intensities. In both systems tropical cyclones are classified from Category 1 (the weakest) to Category 5 (the strongest), and each scale seems to have been adopted enthusiastically by the general public in both Australia and in the United States. However, the scales are very different in their conception and in the boundaries between their respective categories. The Saffir/Simpson scale, used in the United States, is used for classifying tropical cyclones which have reached hurricane intensity while the Australian scale is utilized for all tropical cyclones of gale intensity or higher. Nowadays, anyone anywhere in the world with internet access can follow tropical cyclones in great detail, and there are many persons who delight in tracking and discussing storms in all oceanic basins. Considerable confusion has sometimes arisen when, for example, someone in the U. S. is following an Australian cyclone and assuming that the category given in the BoM warnings (and often aired in the international news media) is equivalent to its Saffir/Simpson category. The following chart summarizes the salient characteristics of the two scales: Characteristic Saffir/Simpson Australian ------------------------------------------------------------------------- Beginning Point Hurricane force Gale force Wind Parameter Sustained wind (1-min avg) Peak gusts Wind Velocity Units Statute miles-per-hour Kilometres-per-hour My purpose here is to provide information whereby persons interested in comparing the two scales can easily do so. Table 1 defines the Saffir/Simpson Scale in terms of the 1-min avg maximum sustained wind (MSW) in statute miles-per-hour (mph) while Table 2 defines the Australian Cyclone Severity Scale in terms of peak wind gusts in kilometres-per-hour (km/hr). I have not included the narrative describing the degree and type of damage which can be expected with each category in both scales. Also, in both tables I have included the qualifying wind velocity in nautical miles-per-hour (kts) along with the nominal central pressure range in millibars (mb)--numerically equal to hectopascals (hPa). Table 1 - Saffir/Simpson Scale ============================== Category 1-min avg MSW 1-min avg MSW Central Pressure S/S (mph) (kts) (mb) --------------------------------------------------------------------- 1 74 - 95 64 - 82 >= 980 2 96 - 110 83 - 95 965 - 979 3 111 - 130 96 - 113 945 - 964 4 131 - 155 114 - 135 920 - 944 5 >= 156 >= 136 <= 919 Table 2 - Australian Cyclone Severity Scale =========================================== Category Peak gusts Peak gusts Central Pressure Aust (km/hr) (kts) (hPa) --------------------------------------------------------------------- 1 90 - 124 49 - 67 986 - 995 2 125 - 169 68 - 91 971 - 985 3 170 - 224 92 - 121 956 - 970 4 225 - 279 122 - 150 930 - 955 5 >= 280 >= 151 <= 929 The following two tables define each scale in terms of the other scale's parameters, i.e., the Saffir/Simpson scale is defined in terms of a 10-min avg MSW in kts, and peak gusts in kts and in km/hr (Table 3) while the Australian scale is defined in terms of a 10-min avg MSW in kts and a 1-min avg MSW in mph (Table 4). Table 3 - Saffir/Simpson Scale in Terms of Australian Scale Parameters ====================================================================== Category 10-min avg MSW Peak Gusts Peak Gusts Equivalent S/S (kts) (kts) (km/hr) Aust Category ------------------------------------------------------------------------- 1 56 - 72 79 - 101 146 - 190 mid-2 to mid-3 2 73 - 84 102 - 118 191 - 220 mid to high-3 3 85 - 99 119 - 140 221 - 260 high-3 to mid-4 4 100 - 118 141 - 166 261 - 310 mid-4 to mid-5 5 >= 119 >= 167 >= 311 mid to high-5 Table 4 - Australian Scale in Terms of Saffir/Simpson Scale Parameters ====================================================================== Category 10-min avg MSW 1-min avg MSW 1-min avg MSW Equivalent Aust (kts) (kts) (mph) S/S Category ------------------------------------------------------------------------- 1 34 - 47 38 - 54 44 - 62 none 2 48 - 64 55 - 73 63 - 84 none to mid-1 3 65 - 85 74 - 96 85 - 111 mid-1 to high-2 4 86 - 106 97 - 120 112 - 139 low-3 to low-4 5 >= 107 >= 120 >= 140 mid-4 and up Finally, as an additional aid to comparison, I have included a table (Table 5) comparing each cyclone scale with the Dvorak scale, used extensively in estimating tropical cyclone intensity from visible and infrared satellite imagery. I have started the table with T2.0 since neither TPC/NHC nor the BoM TCWCs routinely issue advisories/ advices/warnings for systems less than that Dvorak rating. (See the key following the table for an explanation of the abbreviations used.) Table 5 - Comparison of Dvorak Scale with Cyclone Scales ======================================================== Dvorak MSW MSW TPC/NHC Australian T-Number (1-min kts) (10-min kts) Category Category ------------------------------------------------------------------- T2.0 30 26 TD TL ................................................................... T2.5 35 31 TS TL ................................................................... T3.0 45 40 TS TC-1 ................................................................... T3.5 55 48 TS TC-2 ................................................................... T4.0 65 57 H-1 TC-2 ................................................................... T4.5 77 68 H-1 TC-3 ................................................................... T5.0 90 79 H-2 TC-3 ................................................................... T5.5 102 90 H-3 TC-4 ................................................................... T6.0 115 101 H-4 TC-4 ................................................................... T6.5 127 112 H-4 TC-5 ................................................................... T7.0 140 123 H-5 TC-5 ................................................................... T7.5 155 136 H-5 TC-5 ................................................................... T8.0 170 150 H-5 TC-5 ------------------------------------------------------------------- Key to Abbreviations: --------------------- TD tropical depression TL tropical LOW H-n hurricane of Saffir/Simpson category "n" TC-n tropical cyclone of category "n" on Australian scale Most of the information presented above was obtained from the websites of Australia's Bureau of Meteorology and the Tropical Prediction Center/National Hurricane Center. A special thanks to Michael Bath for providing information regarding the nominal central pressures corresponding to the Australian scale categories as well as making some suggestions concerning formatting and presentation of the tables. ************************************************************************* ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for February: No tropical cyclones ************************************************************************* SOUTH ATLANTIC (SAT) - Atlantic Ocean South of the Equator Activity for February: 1 possible tropical cyclone South Atlantic Tropical Activity for February --------------------------------------------- In late February what appeared to be a small tropical storm developed of the coast of southeastern Brazil, but unlike the devastating Catarina of March, 2004, moved away from the coastline with no effects on land. According to Toni Cristaldi of the Melbourne, FL, NWS Forecast Office, in its formative stages on 20 February the system for a brief period of time drifted erratically south-southwestward, parallel to the Brazilian coastline. On the 21st it began a general eastward motion which would continue throughout its short lifetime. Based on an analysis of available satellite imagery by Dr. Karl Hoarau of Cergy-Pontoise University near Paris, the system intensified quickly on the 22nd and reached a peak intensity of 55 kts around 23/0000 UTC at a point approximately 225 nm due east of Porto Alegre, Brazil. Following this, the system encountered strong westerly and southwesterly shear and weakened quickly. Following is a track and intensity history recently compiled by Karl. (A special thanks to Karl for taking the time to prepare the track.) Storm Name: None Cyclone Number: None Basin: SAT Date Time Lat Lon Cent MSW MSW Remarks (GMT) Press 1-min 10-min (mb) (kts) (kts) ------------------------------------------------------------------------- 06 FEB 21 1200 30.8 S 49.7 W 20 06 FEB 21 1800 31.1 S 49.3 W 25 06 FEB 22 0000 31.3 S 49.0 W 25 06 FEB 22 0600 31.4 S 48.6 W 25 06 FEB 22 1200 31.1 S 48.2 W 30 06 FEB 22 1800 30.7 S 47.8 W 35 06 FEB 22 2100 30.3 S 47.4 W 45 06 FEB 23 0000 30.0 S 46.9 W 55 06 FEB 23 0600 29.4 S 45.6 W 50 06 FEB 23 1200 29.2 S 44.3 W 45 06 FEB 23 1800 29.1 S 42.6 W 40 06 FEB 23 2100 29.1 S 41.6 W 30 ************************************************************************* NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for February: No tropical cyclones ************************************************************************* NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for February: No tropical cyclones ************************************************************************* NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for February: No tropical cyclones ************************************************************************* SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E Activity for February: 1 tropical storm 1 intense tropical cyclone Sources of Information ---------------------- The primary sources of tracking and intensity information for Southwest Indian Ocean tropical cyclones are the warnings issued by the Tropical Cyclone Warning Centre on La Reunion Island, part of Meteo France (MFR), and the Regional Specialised Meteorological Centre for the basin. However, tropical cyclones in this region are named by the Sub-regional Tropical Cyclone Advisory Centres in Mauritius and Madagascar with longitude 55E being the demarcation line between their respective areas of naming responsibility. The La Reunion centre only advises these agencies regarding the intensity of tropical systems. References to sustained winds imply a 10-minute averaging period unless otherwise stated. In the companion tropical cyclone tracks file, I occasionally annotate positions from warnings issued by the Joint Typhoon Warning Center (JTWC) of the U. S. Air Force and Navy, located at Pearl Harbor, Hawaii, when they differ from MFR's coordinates by usually 40-50 nm or more. The JTWC warnings are also the source of the 1-minute average maximum sustained wind values included in the tracks file. Additionally, information describing details of satellite imagery and atmospheric circulation features included in the narratives is often gleaned from the JTWC warnings. Southwest Indian Ocean Tropical Activity for February ----------------------------------------------------- As the month of February opened, Tropical Cyclone Boloetse was gaining strength in the southern Mozambique Channel before making a very close approach to southwestern Madagascar. The full report on Boloetse may be found in the January summary. Shortly after mid-month a system formed quickly near Mauritius and was designated Tropical Storm 09 by MFR and TC-12S by JTWC. Mauritius, however, did not upgrade the system to tropical storm status so no name was assigned. During the final week of February and into the opening days of March, Intense Tropical Cyclone Carina tracked southward through the eastward part of the basin, attaining great intensity (115 kts 10-min avg per MFR/130 kts 1-min avg per JTWC) but fortunately remaining far from populated areas. Reports on both Tropical Storm 09 and Tropical Cyclone Carina follow. TROPICAL STORM (MFR-09 / TC-12S) 19 - 21 February ------------------------------------- A. Storm History ---------------- The regular STWO for 18 February issued by JTWC noted that an area of convection had formed approximately 340 nm east-northeast of Antanana- rivo, Madagascar. QuikScat data showed an elongated area of troughing, and water vapor imagery indicated that an upper-level trough was limiting convection on the northern periphery of the surface trough while serving to enhance convection along the southern periphery. The development potential was assessed as 'poor', but this was upgraded to 'fair' at 0700 UTC on 19 February as multi-spectral satellite imagery revealed a well-defined and tight LLCC with increasing deep convection. At 19/0600 UTC MFR issued the first bulletin on Tropical Disturbance 09, placing the center approximately 200 nm northwest of Mauritius. The system began to intensify fairly rapidly--MFR upgraded it to a 30-kt tropical depression at 19/1200 UTC and JTWC issued a TCFA at 1430 UTC. At 19/1800 UTC MFR upgraded the depression to a 40-kt tropical storm centered about 75 nm north-northwest of Mauritius. At the same time, JTWC issued their first warning on TC-12S with the 1-min avg MSW estimated at 45 kts. Tropical Storm 09 was moving southeastward at about 12 kts due to its being under the steering influence of a ridge located to the northeast. Despite its rapid intensification spurt early on the 19th, the tropical storm did not intensify further and soon began to weaken as it entered an unfavorable shear environment. The system swung to more of an easterly track, halted, described a tiny clockwise loop, and then drifted northwestward as it weakened. MFR downgraded Tropical Storm 09 to a tropical depression at 1200 UTC on 20 February, and JTWC issued their final warning six hours later. Shear had separated the remaining convection nearly 90 nm from the LLCC. MFR further down- graded the system to a 25-kt tropical disturbance at 21/0000 UTC and issued their final bulletin, placing the center approximately 85 nm north of Mauritius. A graphic depicting the track of Tropical Storm 09 may be found at the following link: http://www.tropicalcyclone2005.com/database/2006/SOHEM/BT-IMAGES/2006-12S-NONAME.gif> No damages or casualties are known to have resulted from this system. B. Discussion: Why Wasn't This System Named? --------------------------------------------- In the Southwest Indian Ocean west of longitude 90E, Meteo France La Reunion (MFR) serves as the WMO's Regional Specialised Meteorological Centre (RSMC) for the basin, receiving this designation sometime in the early 1990s. However, the meteorological services of Mauritius and Madagascar began naming tropical cyclones in this region in 1960, working from a common list of names with longitude 55E being the demarcation line. At the time that MFR was designated the RSMC, apparently, as a conciliatory gesture due to the long-standing practice, Mauritius and Madagascar were designated as Sub-regional Tropical Cyclone Advisory Centres and allowed to continue the actual assigning of names to tropical systems in this basin. MFR only advises these agencies regarding the intensity of tropical systems. Most of the time there is agreement between MFR and the Sub-regional Centre in question and the name is applied on the first MFR bulletin upgrading a depression to tropical storm status. However, from time to time Mauritius or Madagascar doesn't name a system which MFR has upgraded to a tropical storm, and conversely, there have been occasions when one of the Sub-regional Centres has named a tropical depression which MFR had not yet classified as a tropical storm. This particular case is interesting because of a Weather News bulletin issued by the Mauritius Meteorological Office around 1300 UTC on the 19th of February: "A midget storm is approaching Mauritius from the north-west and at 0400 hrs this afternoon (1200 UTC) it was centered at about 220 km to the north-west of Mauritius in latitude 18.5S and longitude 56.2E and is moving in a southeast direction at about 20 km/hr. Forecast for the next 24 hours: weather will gradually deteriorate over Mauritius with scattered showers heavy at times and isolated thunderstorms. Gusts of the order of 60 km/hr (32 kts) will gradually increase to reach more than 100 km/hr (54 kts) at night." Applying the most commonly-used gust-to-MSW (10-min avg) reduction factor (1.41), peak gusts of 54 kts would imply a 10-min mean wind of 38 kts--above gale force. Dvorak ratings from JTWC and MFR both reached T3.0 late on the 19th and early on the 20th, and satellite intensity estimates from SAB were at 35 kts (T2.5). So it isn't exactly clear why the Mauritius Meteorological Office chose not to name this system. The forecast peak gusts of 54 kts seem to imply a minimal tropical storm, although those were admittedly a forecast and not a current analysis. Also, the agency could have adopted a wait-and-see policy, and the system did begin to weaken fairly quickly. However, the term "midget storm" in the Weather News bulletin makes one wonder if perhaps Mauritius has some sort of minimum size criterion for qualifying a system as a bona fide tropical storm. Tropical Storm 09 was a small system, but not unusually so. JTWC estimated the gale radius at 60 nm, while MFR's radius of gales was considerably smaller at 20 nm. However, according to some information received several years ago from Jeff Callaghan at BoM Brisbane, the incredibly devastating Tropical Cyclone Tracy which devastated Darwin in 1974 had a gale radius of only 18 nm. If anyone reading this discussion can shed any more light on the question raised above, I'll be happy to report on it in a future summary. (Report written by Gary Padgett) INTENSE TROPICAL CYCLONE CARINA (MFR-10 / TC-14S) 23 February - 3 March --------------------------------------------------- Carina: contributed by Mauritius A. Introduction and Storm Origins --------------------------------- Intense Tropical Cyclone Carina became the strongest tropical cyclone of the 2005-2006 season in the Southwest Indian Ocean, at least as of 20 April 2006. The storm almost reached the superlative classification of "very intense tropical cyclone" per MFR's analysis, and equalled a Western Pacific super typhoon per JTWC's nomenclature. Fortunately, Carina pursued a track which kept it several hundred miles distant from any islands. Early on 22 February an area of convection which had appeared the previous day was located approximately 565 nm east of Diego Garcia. The convective signature was improving with bands of deep convection on the northern and southern periphery rotating cyclonically toward a developing LLCC. An upper-level analysis indicated low vertical shear and the possible development of anticyclonic outflow directly above the disturbance. JTWC assessed the potential for further development as 'fair'. MFR initiated bulletins on Tropical Disturbance 10 at 0000 UTC on 23 February, locating the center about 550 nm east-southeast of Diego Garcia. The system was moving slowly in a general southerly direction, and intensification continued at a steady pace. JTWC issued a TCFA at 23/0330 UTC and MFR upgraded the disturbance to a 30-kt tropical depression at 0600 UTC. At the same time, JTWC issued their first warning on TC-14S, estimating the 1-min avg MSW at 35 kts. B. Synoptic History ------------------- MFR upgraded the depression to tropical storm status at 23/1800 UTC with Mauritius assigning the name Carina. Tropical Storm Carina at this juncture was located about 575 nm east-southeast of Diego Garcia and was quasi-stationary. On the 24th the storm embarked on a southwesterly course under the steering influence of a deep-layer ridge to the east. Carina intensified quite slowly over the next couple of days. Vertical shear was low, but upper-level outflow was less than ideal. JTWC upped the 1-min avg MSW to 70 kts at 25/0600 UTC, but MFR did not upgrade Carina to tropical cyclone (i.e., hurricane) status until 1200 UTC on 26 February. At this time the cyclone's center was located approximately 565 nm southeast of Diego Garcia, moving south-southwestward at 4 kts. On the 26th and 27th Carina moved almost due southward due to the influence of an anticyclone situated to the east, but a return to a southwesterly trajectory was anticipated in a couple of days as a secondary anticyclone was forecast to become established poleward of the cyclone. A NOAA-15 EIR picture taken at 26/0025 UTC revealed some very cold cloud tops associated with Carina. Several tops were at least -100 C with the coldest at -102.3 C near the cyclone's center. Carina continued to intensify steadily and reached its peak intensity of 115 kts (10-min avg) with an estimated CP of 910 hPa at 1200 UTC on 28 February. JTWC's peak 1-min avg MSW of 130 kts correlates very well with MFR's peak intensity. Had Carina's 10-min avg MSW increased by 5 kts more, it would have been classified as a "very intense tropical cyclone"--the highest classification on MFR's scale. At the time of its peak intensity Carina was centered about 650 nm southeast of Diego Garcia, moving slowly southwestward at 5 kts. The slow southwesterly motion continued until around 0000 UTC on 2 March, when Carina made an abrupt turn to the southeast. After peaking in intensity the cyclone weakened very slowly at first, then rather rapidly as vertical shear increased and the outflow became disrupted. JTWC's 1-min avg MSW dropped from 115 kts at 0600 UTC on 1 March to 65 kts twelve hours later. MFR's intensity fell from 110 kts to 75 kts during the same period. Carina was downgraded to a 55-kt tropical storm at 02/1200 UTC as it appeared to describe a small clockwise loop. JTWC issued their final warning at 02/1800 UTC. A 02/1540 UTC SSM/I pass had depicted a fully-exposed LLCC nearly 135 nm to the northwest of the convection. MFR issued bulletins on Carina for another 18 hours, downgrading the system to a tropical disturbance and issuing the final bulletin at 03/1200 UTC. The weak 25-kt center was then estimated to be about 900 nm east of Rodrigues Island. A graphic depicting the track of Intense Tropical Cyclone Carina may be found at the following link: http://www.tropicalcyclone2005.com/database/2006/SOHEM/BT-IMAGES/2006-14S-CARINA.gif> C. Damage and Casualties ------------------------ As Carina was a completely marine cyclone remaining far from any populated areas, there have no reports of damages or casualties resulting from the cyclone. (Report written by Gary Padgett) ************************************************************************* NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E Activity for February: 1 tropical cyclone Sources of Information ---------------------- The primary sources of tracking and intensity information for Northwest Australia/Southeast Indian Ocean tropical cyclones are the warnings and advices issued by the Tropical Cyclone Warning Centres at Perth, Western Australia, and Darwin, Northern Territory. References to sustained winds imply a 10-minute averaging period unless otherwise stated. In the companion tropical cyclone tracks file, I occasionally annotate positions from warnings issued by the Joint Typhoon Warning Center (JTWC) of the U. S. Air Force and Navy, located at Pearl Harbor, Hawaii, when they differ from the Australian centres' coor- dinates by usually 40-50 nm or more. The JTWC warnings are also the source of the 1-minute average maximum sustained wind values included in the tracks file. Additionally, information describing details of satellite imagery and atmospheric circulation features included in the narratives is often gleaned from the JTWC warnings. TROPICAL CYCLONE EMMA (TC-15S) 26 - 28 February ----------------------------------------- A. Origins and Synoptic History ------------------------------- Tropical Cyclone Emma was a short-lived, minimal tropical cyclone which made landfall near Onslow, Western Australia, on the final day of February. A weak tropical LOW had formed as early as 22 February southeast of Java near 12.0S/119.0E, but wasn't expected to develop into a tropical cyclone anytime within the next few days. On the 24th a monsoon trough extended east-west in the Timor Sea along latitude 12S, and a LOW was expected to form over the next couple of days in the vicinity of longitude 115E with a high probability of tropical cyclogenesis during the succeeding days. BoM Perth began issuing shipping warnings and tropical cyclone advices at 0000 UTC on 26 February for a developing tropical LOW located about 450 nm north of Karratha, moving slowly southward. The system continued generally southward over the next couple of days with a couple of relocations. The initial intensity of 25 kts was upped to 30 kts at 26/1200 UTC, and a STWO issued by JTWC at 1800 UTC noted that a 26/1018 UTC QuikScat pass had depicted a very broad LLCC with a uniform wind field of 15 to 20 kts along the periphery and lighter winds near the center--a feature typical of monsoon LOWs. A 26/1459 UTC AMSU-B image revealed that most of the deep convection was confined to the periphery of the circulation. An upper-level analysis revealed that an upper-level anticyclone lay over the surface LLCC, and with low vertical shear and excellent radial outflow, the potential for development was rated as 'fair'. BoM Perth upgraded the LOW to Tropical Cyclone Emma at 1200 UTC on 27 February, placing the center about 165 nm north of Onslow and moving southward at an increased pace of about 14 kts. JTWC issued the first of only two warnings on Emma at 27/1800 UTC, numbering the system as TC-15S. The remarks noted that deep convection had recently migrated from the periphery of the circulation to near the LLCC. Tropical Cyclone Emma reached an estimated peak intensity of 40 kts (10-min avg) at 27/1800 UTC and this was maintained until landfall around 0300 UTC 28 February just west of Mardie. The final tropical cyclone advice on Emma was issued at 28/0600 UTC and placed the center about 130 km east-southeast of Onslow, moving south-southeastward at 28 km/hr (15 kts). This advice downgraded Emma to a 30-kt tropical LOW and further weakening was anticipated. A graphic depicting the track of Tropical Cyclone Emma may be found at the following link: http://www.tropicalcyclone2005.com/database/2006/SOHEM/BT-IMAGES/2006-15S-EMMA.gif> B. Meteorological Observations ------------------------------ Matthew Saxby has sent me some files of observations downloaded from BoM's website. The most notable 24-hour rainfall measured in association with Tropical Cyclone Emma was 190 mm at Karratha in the 24 hours ending at 9:00 AM (presumably local time) on 28 February. Following are the peak winds observed at various weather stations in the region. The criterion for inclusion was that gusts exceeding 40 kts and/or sustained winds exceeding gale force were recorded Station Date Time Peak Sustained Peak Gust (UTC) (10-min avg kts) (3-sec kts) ------------------------------------------------------------------------ Barrow Island 27 Feb 2030 41 49 Bulga Downs 28 Feb 2200 40 -- Karratha 27 Feb 1918 -- 43 Legendre Island 27 Feb 1600 42 -- Meekatharra 28 Feb 1800 -- 45 Mount Magnet 28 Feb 1843 -- 40 Onslow Airport 28 Feb 0125 -- 40 Port Hedland 27 Feb 2132 40 48 Roebourne 27 Feb 2000 35 47 C. Damage and Casualties ------------------------ No reports of damage or casualties resulting from Tropical Cyclone Emma have been received. (Report written by Gary Padgett) ************************************************************************* NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E Activity for February: 1 tropical cyclone Sources of Information ---------------------- The primary sources of tracking and intensity information for Northeast Australia/Coral Sea tropical cyclones are the warnings and advices issued by the Tropical Cyclone Warning Centres at Brisbane, Queensland, and Darwin, Northern Territory, and on very infrequent occasions, by the centre at Port Moresby, Papua New Guinea. References to sustained winds imply a 10-minute averaging period unless otherwise stated. In the companion tropical cyclone tracks file, I occasionally annotate positions from warnings issued by the Joint Typhoon Warning Center (JTWC) of the U. S. Air Force and Navy, located at Pearl Harbor, Hawaii, when they differ from the Australian centres' coor- dinates by usually 40-50 nm or more. The JTWC warnings are also the source of the 1-minute average maximum sustained wind values included in the tracks file. Additionally, information describing details of satellite imagery and atmospheric circulation features included in the narratives is often gleaned from the JTWC warnings. TROPICAL CYCLONE KATE (TC-13P) 22 - 24 February ----------------------------------------- A. Origins and Synoptic History ------------------------------- Tropical Cyclone Kate was a short-lived cyclone in the far north- western Coral Sea. Kate originated from a weak tropical LOW embedded in the monsoon trough near Torres Strait. On 22 February the LOW rapidly intensified as it tracked eastwards. By 22/1800 UTC the LOW was located near 10.8S/144.5E (approximately 130 nm east of Thursday Island, Australia) with a CP of 995 hPa. Gales had wrapped around the LLCC and BoM Brisbane code-named the new cyclone Kate. The cyclone continued to drift to the east-southeast at 7 kts as it was steered by the near-equatorial ridge to the north. The peak intensity of 985 hPa with a MSW of 50 kts (10-min avg) was achieved near 11.3S/146.4E, or approximately 120 nm south-southwest of Port Moresby, New Guinea, at 23/0600 UTC. Soon after, Kate stalled and strong vertical wind shear ripped the cyclone's convective structure away to the southeast of the LLCC. By 24/0000 UTC, Kate had lost cyclone status near 11.3S/146.5E. Peripheral gales persisted to the east and south of the LLCC for a further 24 hours before the remnant LOW dissipated. A graphic depicting the track of Tropical Cyclone Kate may be found at the following link: http://www.tropicalcyclone2005.com/database/2006/SOHEM/BT-IMAGES/2006-13P-KATE.gif> A satellite image of Kate is available at: http://earthobservatory.nasa.gov/NaturalHazards/shownh.php3?img_id=13379> B. Damage and Casualties ------------------------ The cyclone inflicted rough seas through the Torres Strait Islands and along the southern coastline of Papua New Guinea. In the Torres Strait Islands, high tides and rough seas caused further erosion adding to that caused by Tropical Cyclone Ingrid of March, 2005, and the unnamed Port Moresby cyclone of April, 2005 (see reports on those cyclones in their respective monthly summaries) and the gales of July 2005. This erosion washed away a jetty. Following is an excerpt from a press release describing the damage caused to southern Papua New Guinea by gales in July, 2005. A very large HIGH over New South Wales caused gales from the northern Coral Sea to southern Papua New Guinea. "It is understood that king tides caused havoc in Western and Gulf provinces of Papua New Guinea. More than 200 houses, mostly in Western Province and at least one village on the Gulf and Central Province were reported as having been destroyed by surging high tides. Rising tides and rough seas also affected the Madang, New Ireland and Milne Bay provinces. Unprecedented levels of water had swept into food gardens on Carteret Island, Mortlocks and Tasman Islands in Bougainville and in some of the Trobriand Islands. Ten fishermen were reported as missing near Daru." (Report written by Simon Clarke, based in part upon information supplied by Jeff Callaghan of the Brisbane TCWC) ************************************************************************* SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E Activity for February: 3 tropical depressions 1 tropical cyclone of hurricane intensity Sources of Information ---------------------- The primary sources of tracking and intensity information for South Pacific tropical cyclones are the warnings and advisories issued by the Tropical Cyclone Warning Centres at Nadi, Fiji (for waters north of latitude 25S), and Wellington, New Zealand (for waters south of latitude 25S). References to sustained winds imply a 10-minute averaging period unless otherwise stated. In the companion tropical cyclone tracks file, I occasionally annotate positions from warnings issued by the Joint Typhoon Warning Center (JTWC) of the U. S. Air Force and Navy, located at Pearl Harbor, Hawaii, when they differ from the Southern Hemisphere centres' coordinates by usually 40-50 nm or more. The JTWC warnings are also the source of the 1-minute average maximum sustained wind values included in the tracks file. Additionally, information describing details of satellite imagery and atmospheric circulation features included in the narratives is often gleaned from the JTWC warnings. South Pacific Tropical Activity for February -------------------------------------------- As the month of February opened the remnants of January's Tropical Cyclone Jim were loitering about over the ocean southeast of New Caledonia, but redevelopment was not expected and none occurred. The only named cyclone to form was Vaianu, which formed during the 2nd week of the month between Fiji and Samoa and reached hurricane intensity, affecting some of the islands of the Kingdom of Tonga and causing significant agricultural losses. A report on Tropical Cyclone Vaianu, written by Simon Clarke, follows. Three additional tropical depressions were tracked by RSMC Nadi during February. The first of these, Tropical Depression 10F, was first noted at 0600 UTC on 2 February when it was centered only about 80 nm south- west of Niue. Diffluence over the system was good but shear was too strong for it to ever consolidate its associated convection near the LLCC. TD-10F moved erratically in a general southerly direction over the next couple of days and was last referenced at 0600 UTC on the 4th, at which time it had moved to a position about 400 nm southeast of Tongatapu. Warnings were issued for peripheral gales in the eastern semicircle on 3 and 4 February. A graphic depicting the track of this depression may be found at the following link: http://www.tropicalcyclone2005.com/database/2006/SOHEM/BT-IMAGES/2006-10F.gif> Tropical Depression 11F had formed by 2100 UTC on 8 February about 150 nm southwest of Pago Pago, American Samoa. This system drifted slowly south and southwestward over the next couple of days. Vertical shear was not particularly high and some models forecast this system to develop, but it appears that interference from the developing TD-12F to the northwest, which became Tropical Cyclone Vaianu, was a primary inhibiting factor to further development. The last reference to TD-11F was at 10/2100 UTC and placed the center approximately 225 nm west- southwest of Niue. A graphic depicting the track of this depression may be found at the following link: http://www.tropicalcyclone2005.com/database/2006/SOHEM/BT-IMAGES/2006-11F.gif> Tropical Depression 13F was a persistent but weak system which roamed waters from east of the Solomons to well south of Fiji for nearly a week in late February. TD-13F was located about 365 nm east-southeast of Guadalcanal at 2100 UTC on 19 February, and over the next several days moved slowly in a general southeasterly direction, passing between Vanuatu and Fiji on the 22nd and 23rd. The system became quasi- stationary to the south of Fiji on the 25th and was last referenced by the Nadi TCWC at 25/1800 UTC, when it was located roughly 400 nm south-southwest of Viti Levu. As is often the case with these South Pacific depressions forming in a monsoon trough, vertical shear was sufficiently strong to prevent TD-13F from developing as a tropical cyclone. Winds near the center were never estimated stronger than 25 kts, although as the system moved southward toward a subtropical ridge, the increasing pressure gradient was responsible for causing some peripheral gales well south of the center. A graphic depicting the track of this depression may be found at the following link: http://www.tropicalcyclone2005.com/database/2006/SOHEM/BT-IMAGES/2006-13F.gif> TROPICAL CYCLONE VAIANU (TD-12F / TC-11P) 9 - 19 February ------------------------------------------- A. Storm Origins ---------------- Early in February, an active area of convergence developed across the Southeast Pacific from the Solomon Islands through to Tonga. On 9 February an eastward-moving tropical LOW developed approximately 80 nm to the north-northeast of Vanua Levu. As the LOW continued to track steadily to the east, early development was hampered by strong upper-level shear of 20 to 25 kts. The main convective band remained about 1 degree to the east of the LLCC. By 10/1200 UTC, the LOW was located just 30 nm to the north of Niuafo'ou and commenced a path to the south-southeast, slowly strengthening over seas of 29-30 C. The upper-level outflow was diffluent and the system tracked into an area of decreasing shear to its south. B. Synoptic History ------------------- By 11/1100 UTC, organization had undergone marked improvement with the primary convective band wrapping around the LLCC. The LOW was upgraded to cyclone status and named Vaianu. At this time the cyclone was located near 17.4S/174.9W, approximately 85 nm southwest of Niuatoputapu, and had swung back to a 5-kt southwesterly path, being steered by a mid-level ridge to the southeast. The cyclone continued to track in a southwesterly direction at 7 kts over the open ocean to the west of the Tongan group of islands while slowly strengthening as the upper-level wind shear relaxed. Peak intensity of 965 hPa with an estimated MSW (10-min avg) of 70 kts was reached at 13/1200 UTC at 21.7S/177.0W, or approximately 105 nm west-southwest of Tongatapu, and this intensity was sustained for a further 24 hours as Vaianu swung onto a southward track midway between Ono-i-lau (in Fiji's Lau archipelago) and Tongatapu (passing about 100 nm from each). The cyclone eventually re-curved to the southeast at 10 kts, being steered by a mid-level ridge to the northeast and by a broad 250-hPa trough to the west. The storm gradually weakened due to increasing wind shear and cooler SSTs. Vaianu lost cyclone status whilst undergoing extratropical transition near 29.0S/167.0W, or roughly 600 nm southwest of Rarotonga, at 16/1200 UTC, but remained a powerful low pressure system for several days thereafter while tracking generally to the east over open ocean. A graphic depicting the track of Tropical Cyclone Vaianu may be found at the following link: http://www.tropicalcyclone2005.com/database/2006/SOHEM/BT-IMAGES/2006-11P-VAIANU.gif> Satellite images of Vaianu can be found at: http://earthobservatory.nasa.gov/NaturalHazards/shownh.php3?img_id=13369> http://visibleearth.nasa.gov/view_rec.php?id=8376> C. Damage and Casualties ------------------------ Vaianu managed to move between the islands on its path across the South Pacific, and as a consequence the main impacts of the cyclone were associated with torrential rain and gale-force winds. Tropical food crops were hard hit by Vaianu, particularly in Tongatapu and Eua, with 70% of the banana and breadfruit crops being wiped out. Sea water intruded inland about 100 m on the northwestern side of Tongatapu. However, little damage to property was reported. There were no reports of any significant damage to housing. Electricity supplies were knocked out in many areas along Vaianu's path and this took about a week to restore to all outer villages and nearby islands. Flooding was reported in low-lying areas of Tonga's capital, Nuku'alofa, "shutting down" the city for two days. Shops and offices were closed with windows boarded up as Vaianu passed by approximately 55 nm to the east. The remaining Tongan islands were affected by strong winds, thunderstorms and very rough seas but no substantial damage or injuries were reported. (Report written by Simon Clarke) ************************************************************************* SPECIAL FEATURE - SOURCES OF TROPICAL CYCLONE INFORMATION The purpose of this section is to list some websites where many and varied types of tropical cyclone information are archived. Many readers will know about these already, but for the benefit of those who don't, I wanted to include them. (1) Aircraft Reconnaissance Information --------------------------------------- Various types of messages from reconnaissance aircraft may be retrieved from the following FTP site: ftp://ftp.nhc.noaa.gov/pub/products/nhc/recon/> Information regarding how to interpret the coded reconnaissance messages may be found at the following URL: http://www.nhc.noaa.gov/reconlist.shtml> Links are also included to websites with further information about the U. S. Air Force 53rd Weather Reconnaissance Squadron and the NOAA Air- craft Operations Center. (2) Archived Advisories ----------------------- All the advisory products (public advisories, forecast/advisories, strike probabilities, discussions, various graphics) issued by TPC/NHC are archived on TPC's website. For the current year (using 2004 as an example), the archived products can be found at: http://www.nhc.noaa.gov/archive/2004/index.shtml> Links to tropical products archives for earlier years are available at the following URL: http://www.nhc.noaa.gov/pastall.shtml> JTWC warnings for past storms are archived on the NRL Monterry website: http://www.nrlmry.navy.mil/tc_pages/tc_home.html> On the NRL site, the link to past years can be found in the upper left corner of the screen. I am not aware at the moment of any other TCWC which archives all its tropical cyclone warning/advisory products for public access, but if I learn of any, I will add them to this list. (3) Satellite Imagery --------------------- Satellite images of tropical cyclones in various sensor bands are available on the NRL Monterrey and University of Wisconsin websites, courtesy of Jeff Hawkins and Chris Velden and their associates. The links are: http://www.nrlmry.navy.mil/tc_pages/tc_home.html> http://cimss.ssec.wisc.edu/tropic/tropic.html> On the NRL site, the link to past years can be found in the upper left corner of the screen. For the CIMSS site, a link to data archives is located in the lower left portion of the screen. Additional tropical satellite imagery, along with looping ability for composite microwave imagery for the Western Hemisphere north of the equator, can be found at: (1) For the Eastern North Pacific: http://www.ssd.noaa.gov/PS/TROP/trop-epac.html> (2) For the Atlantic, Gulf of Mexico and Caribbean Sea: http://www.ssd.noaa.gov/PS/TROP/trop-atl.html> I'm sure there are other sites with available imagery available, and as I learn of them, I will add the links to this list. ************************************************************************* EXTRA FEATURE In order to shorten the amount of typing in preparing the narrative material, I have been in the habit of freely using abbreviations and acronyms. I have tried to define most of these with the first usage in a given summary, but I may have missed one now and then. Most of these are probably understood by a majority of readers but perhaps a few aren't clear to some. To remedy this I developed a Glossary of Abbreviations and Acronyms which I first included in the August, 1998 summary. I don't normally include the Glossary in most months in order to help keep them from being too long. If anyone would like to receive a copy of the Glossary, please e-mail me and I'll be happy to send them a copy. ************************************************************************* AUTHOR'S NOTE: This summary should be considered a very preliminary overview of the tropical cyclones that occur in each month. The cyclone tracks (provided separately) will generally be based upon operational warnings issued by the various tropical cyclone warning centers. The information contained therein may differ somewhat from the tracking and intensity information obtained from a "best-track" file which is based on a detailed post-seasonal analysis of all available data. Information on where to find official "best-track" files from the various warning centers will be passed along from time to time. The track files are not being sent via e-mail. They can be retrieved from the archive sites listed below. (Note: I do have a limited e-mail distribution list for the track files. If anyone wishes to receive these via e-mail, please send me a message.) Both the summaries and the track files are standard text files created in DOS editor. Download to disk and use a viewer such as Notepad or DOS editor to view the files. The first summary in this series covered the month of October, 1997. Back issues can be obtained from the following websites (courtesy of Michael Bath, Michael V. Padua, Michael Pitt, Chris Landsea, and John Diebolt): http://australiasevereweather.com/cyclones/> http://www.typhoon2000.ph> http://mpittweather.com> ftp://ftp.aoml.noaa.gov/hrd/pub/landsea/padgett/> http://www.tropicalcyclone2005.com/> Another website where much information about tropical cyclones may be found is the website for the UK Meteorological Office. Their site contains a lot of statistical information about tropical cyclones globally on a monthly basis. The URL is: http://www.metoffice.gov.uk/weather/tropicalcyclone> TROPICAL CYCLONE REPORTS AVAILABLE JTWC now has available on its website the Annual Tropical Cyclone Report (ATCR) for 2004 (2003-2004 season for the Southern Hemisphere). ATCRs for earlier years are available also. The URL is: http://199.10.200.33/jtwc.html> Also, TPC/NHC has available on its webpage nice "technicolor" tracking charts for the 2004 Atlantic and Eastern North Pacific tropical cyclones; also, storm reports for all the 2004 Atlantic and Eastern North Pacific cyclones are now available, as well as track charts and reports on storms from earlier years. The URL is: http://www.nhc.noaa.gov> A special thanks to Michael Bath of McLeans Ridges, New South Wales, Australia, for assisting me with proofreading the summaries. PREPARED BY Gary Padgett E-mail: [email protected] Phone: 334-222-5327 Kevin Boyle (Eastern Atlantic, Western Northwest Pacific, South China Sea) E-mail: [email protected] Simon Clarke (Northeast Australia/Coral Sea, South Pacific) E-mail: [email protected] ************************************************************************* *************************************************************************
Document: summ0602.htm
Updated: 28th April 2006 |
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