AWCN16 CWHX 231857 SPECIAL WEATHER SUMMARY MESSAGE FOR NEWFOUNDLAND AND LABRADOR ISSUED BY ENVIRONMENT CANADA AT 4:27 PM NDT THURSDAY 23 SEPTEMBER 2010. THIS IS A FOLLOWUP SUMMARY OF INFORMATION AND METEOROLOGICAL DATA FROM HURRICANE IGOR'S IMPACT IN NEWFOUNDLAND ON MONDAY AND TUESDAY SEPTEMBER 20TH AND 21ST 2010. THE INITIAL BULLETIN CONTAINING STORM DATA WAS ISSUED UNDER THIS SAME HEADER AT 4:47 AM NDT ON SEPTEMBER 22ND. THE PURPOSE OF THIS FOLLOWUP SUMMARY IS TO FOCUS SPECIFICALLY ON THE METEOROLOGICAL ASPECTS AND TO SERVE AS AN UPDATE TO THE DATA AND PROVIDE AN HISTORICAL PERSPECTIVE. THE EXTREME WEATHER EVENT THAT CAUSED SEVERE FLOODING AND HEAVY WIND DAMAGE OVER EASTERN NEWFOUNDLAND EARLY THIS WEEK WAS RELATED TO THE COMBINED EFFECTS OF HURRICANE IGOR AND A STATIONARY FRONT THAT HAD PREVIOUSLY DEVELOPED TO THE NORTH OF THE HURRICANE. THE FRONT WAS ASSOCIATED WITH A SHARP TROUGH OF LOW PRESSURE IN THE UPPER ATMOSPHERE WHICH PROVIDED A SIGNIFIGANT AMOUNT OF ENERGY TO THE HURRICANE. THIS PREDICTED INTERACTION EXPLAINS WHY THE HURRICANE DID NOT WEAKEN OVER THE COOLER OCEAN WATERS SOUTH OF NEWFOUNDLAND. IN FACT THE INTENSITY OF IGOR INCREASED AS A RESULT OF THE TROUGH WHILE THE CENTRE OF THE STORM APPROACHED THE AVALON PENINSULA TUESDAY MORNING SEPTEMBER 21ST. THE CENTRE OF THE STORM (THE AREA OF LOWEST PRESSURE) DID NOT ACTUALLY CROSS LAND, SO THE HURRICANE DID NOT TECHNICALLY MAKE LANDFALL. HOWEVER, THE AREAS OF HIGHEST RAINFALL AND WIND WERE DIRECTLY OVER THE EASTERN PENINSULAS OF THE ISLAND. ADDITIONALLY, IGOR WAS STILL AT HURRICANE STATUS AS IT TRACKED JUST OFFSHORE OF THE AVALON PENINSULA. AS THE CENTRE PASSED TO THE NORTHEAST OF ST JOHN'S TUESDAY AFTERNOON, IGOR WAS THEN CLASSIFIED AS BEING POST-TROPICAL. THIS RECLASSIFICATION DOES NOT ALWAYS IMPLY A DOWNGRADE IN STORM INTENSITY AS WAS THE CASE WITH IGOR WHEN THE MAXIMUM WINDS IN THE STORM INCREASED FROM ABOUT 120 KM/H TO 140 KM/H AS IT APPROACHED NEWFOUNDLAND. THE SIZE OF THE HURRICANE - EVEN PRIOR TO ITS TRANSITION TO A POST-TROPICAL STORM - WAS IMPRESSIVE. THIS CONTRIBUTED IN PART TO THE LARGE IMPACT AREA OF SEVERE RAINFALL AND WINDS. THERE HAVE BEEN STORMS OF THIS TYPE OVER THE PAST DECADE THAT DELIVERED SIMILAR WINDS AND RAINFALL, BUT THE AREAS AFFECTED WERE MUCH MORE LOCALIZED. RECENT SEVERE RAINFALL EVENTS INCLUDE TROPICAL STORM CHANTAL OF 2007 AND GABRIELLE OF 2001 WHICH CAUSED MAJOR FLOODING AND ROAD WASHOUTS ON PARTS OF THE AVALON PENINSULA. HIGH WIND EVENTS OF SIMILAR INTENSITY BUT OVER MUCH SMALLER AREAS INCLUDE HURRICANE MICHAEL OF 2000 AND POST-TROPICAL STORM FLORENCE OF 2006. THESE EVENTS BOTH CAUSED STRUCTURAL DAMAGE TO BUILDINGS IN THE HARBOUR BRETON AND CONNAIGRE PENINSULA REGIONS OF NEWFOUNDLAND. THE FRONT THAT HAD DEVELOPED NORTH OF THE HURRICANE WAS THE PRIMARY FEATURE LEADING TO THE SEVERE RAINFALLS SINCE IT SERVED AS A CONDUIT FOR MOISTURE MOVING NORTH FROM IGOR. THE VERY HIGH WINDS WERE A COMBINATION OF THE CIRCULATION FROM THE HURRICANE ITSELF BUT SIGNIFICANTLY EXACERBATED BY THE PUSH OF COOL AND UNSTABLE AIR FROM THE TROUGH IN THE UPPER ATMOSPHERE DISCUSSED ABOVE. THIS WAS THE SOURCE OF IGOR'S RENEWED ENERGY AND REASON FOR THE NORTHWARD BEND IN THE STORM'S HEADING AS IT APPROACHED THE AVALON PENINSULA. EVENT (FRONT/HURRICANE) TOTAL RAINFALLS FROM OFFICIAL AND OTHER SOURCES: -------------------------------------------------------- ST. LAWRENCE 238 MM BONAVISTA 200+ MM (* SEE NOTE BELOW) LETHBRIDGE (PRIVATE STATION) 194 MM ST. PIERRE/MIQUELON 160 MM POUCH COVE 142 MM (HAM RADIO NETWORK) ST. JOHN'S WEST 134 MM BAY D'ESPOIR (GENERATOR STN) 124 MM GANDER (AIRPORT) 124 MM ST. JOHN'S (AIRPORT) 120 MM CAPE RACE 54 MM (** SEE NOTE BELOW) BURGEO 41 MM 100 MM = 4 INCHES, 200 MM = 8 INCHES * STOPPED REPORTING RAINFALL AMOUNTS AT 1:30PM TUESDAY HOWEVER SIGNIFICANT RAINFALL STILL OCCURRED FOR SEVERAL HOURS AFTER BASED ON RADAR AND CITIZEN REPORTS. ** DID NOT REPORT BETWEEN 1:30 PM AND 5:30 PM ON TUESDAY AS IGOR WAS MOVING AWAY. -> OTHER PRIVATE STATIONS THAT WERE WITHIN THE HEAVIEST RAINFALL ZONE HAVE NOT YET COME IN WITH THEIR TOTAL AMOUNTS - THEY INCLUDE BROWNSDALE AND PORT UNION IN THE TRINITY BAY AREA EAST OF BONAVISTA. PEAK WIND SPEEDS FROM OFFICIAL AND OTHER SOURCES: -------------------------------------------------------- CAPE PINE 172 KM/H * (122+ KM/H SUSTAINED) SAGONA ISLAND 163 KM/H (113 KM/H SUSTAINED) *** BONAVISTA 155 KM/H (122 KM/H SUSTAINED) *** POUCH COVE 147 KM/H ** POOL'S ISLAND 146 KM/H (104 KM/H SUSTAINED) *** ST. JOHN'S (AIRPORT) 137 KM/H (92 KM/H SUSTAINED) GRATE'S COVE 135 KM/H ST. PIERRE 135 KM/H (91 KM/H SUSTAINED) ARGENTIA 132 KM/H TWILLINGATE 131 KM/H ST. LAWRENCE 124 KM/H ST. JOHN'S WEST 117 KM/H WINTERLAND 111 KM/H ENGLEE 111 KM/H GANDER 109 KM/H CAPE RACE 106 KM/H BURGEO 100 KM/H STEPHENVILLE 98 KM/H PORT AUX BASQUES 95 KM/H ST. ANTHONY 81 KM/H * PRIVATE STATION SOUTHWEST OF TREPASSEY ON SOUTHERN AVALON. ** HAM RADIO NETWORK *** SUSTAINED WIND IS THE AVERAGE WIND SPEED OVER A 10 MINUTE PERIOD. -> CATEGORY-1 HURRICANE FORCE WIND IS 118 KM/H, CATEGORY-2 IS 155 KM/H AND CATEGORY-3 IS 178 KM/H. -> CAPE RACE DATA NOT YET KNOWN SINCE THE STATION WENT OFFLINE DURING THE PERIOD OF EXTREME WINDS. MARINE/BUOY DATA: BUOY WIND GUST SIG/PK WAVE LOWEST PRESSURE -------------------------------------------------------- 44139 138 KM/H 9/17 M * 970 MB 44251 135 KM/H 8/16 M 952 MB 44138 123 KM/H 13/25 M 957 MB 44140 98 KM/H 13/21 M 976 MB 44255 90 KM/H 4/7 M 985 MB -> WAVE UNITS ARE IN METERS. 'SIG WAVE' BASICALLY REPRESENTS THE AVERAGE WAVE HEIGHT AND 'PK WAVE' REPRESENTS THE MAXIMUM WAVE HEIGHT. -> UNIT OF PRESSURE (MB = MILLIBAR) USED COMMONLY IN METEOROLOGY. * DATA RECORD FROM THIS BUOY ACTUALLY INDICATES A MAX OF 28 M WHICH WILL REQUIRE FURTHER ANALYSIS TO VERIFY. -> A STORM SURGE OF 70 TO 100 CM WAS PREDICTED AND OBSERVED FROM BONAVISTA SOUTHWARD TO ARGENTIA AROUND THE AVALON PENINSULA. INFORMATION ON RECORDS AND THE RARITY OF RAINFALL, WIND AND THE EVENT IN GENERAL: -------------------------------------------------------- HURRICANE IGOR AND ITS SEVERE IMPACTS CERTAINLY REPRESENT A RARE EVENT IN NEWFOUNDLAND WHICH HAS BEEN DESCRIBED AS THE WORST IN MEMORY. IN STATISTICAL TERMS, THIS WAS EFFECTIVELY A 50-100 YEAR EVENT DEPENDING ON HOW ONE CHOSES TO DEFINE IT. THERE ARE NO HURRICANES/POST-TROPICAL EVENTS OF THIS MAGNITUDE STRIKING NEWFOUNDLAND IN THE MODERN ERA. HURRICANE JUAN IN NOVA SCOTIA WAS THE LAST ATLANTIC CANADIAN HURRICANE TO CAUSE EXTREME DAMAGE. PRIOR TO THE NAMING OF HURRICANES, THE 1935 "NEWFOUNDLAND HURRICANE" 75 YEARS AGO WAS OF SIMILAR INTENSITY AND POTENTIAL LOW PRESSURE TROUGH INTERACTION. MORE ANALYSIS IS NEEDED TO MAKE SPECIFIC COMPARISONS TO HISTORIC STORMS. THE RAINFALL OF 238 MM AT ST. LAWRENCE DURING IGOR IS UNPRECEDENTED FOR THAT LOCATION. MANY OF THE OTHER STATIONS REPORTING 150 MM+ SET NEW RECORDS - AMOUNTING TO A 100-YEAR+ RAINFALL EVENT. IN TERMS OF WIND SPEEDS, NO ALL-TIME RECORDS WERE BROKEN, HOWEVER, THE WIND SPEEDS WERE RARE FOR SEPTEMBER (ABOUT ONCE EVERY 50 YEARS) AND THE BROAD AREA OF THOSE EXTREME WINDS WAS EVEN RARER FOR THIS TIME OF YEAR. WINDS OF THIS MAGNITUDE DURING IGOR OCCUR ABOUT ONCE EVERY 5 TO 10 YEARS IN EASTERN NEWFOUNDLAND - INCLUDING INTENSE WINTER STORMS. SOME DATA FROM SIMILAR EVENTS OVER THE PAST TEN YEARS IN NEWFOUNDLAND: -------------------------------------------------------- HURRICANE MICHAEL (OCTOBER 2000): PEAK WIND OVER LAND WAS SIMILAR TO IGOR, 172 KM/H AT ST. LAWRENCE ON THE SOUTHERN BURIN PENINSULA. HIGHEST SUSTAINED WIND DURING MICHAEL WAS 128 KM/H AT SAGONA ISLAND. TROPICAL STORM GABRIELLE (SEPTEMBER 2001): 175 MM FELL IN THE ST. JOHN'S AREA CAUSING MAJOR FLOODING. HEAVIEST RAIN LOCALIZED TO EASTERN AVALON. POST-TROPICAL STORM FLORENCE (SEPTEMBER 2006): A HURRICANE-FORCE EVENT MUCH LIKE IGOR WITH THE SAME PEAK WIND AT SAGONA ISLAND AS IGOR (163 KM/H). WIND DAMAGE WAS NOWHERE NEAR AS WIDESPREAD. IN FRANCOIS EAST OF BURGEO A HOME WAS BLOWN OFF ITS FOOTINGS AND OVER AN EMBANKMENT. TROPICAL STORM CHANTAL (AUGUST 2007): 150-200 MM OF RAINFALL WAS RECORDED IN THE ARGENTIA AND WHITBOURNE AREAS OF THE AVALON PENINSULA. SOME COMMUNITIES WERE CUT-OFF DUE TO ROAD WASHOUTS. THE TROPICAL STORM MERGED WITH A STATIONARY FRONT SIMILAR TO IGOR, BUT THE RAINFALL NOT AS WIDESPREAD. END/CHC/NLWO