Tropical Storm Igor – A new tropical storm name Igor has formed in the mid-Atlantic and it may turn out to be a monster of a storm as its projected to be a Category 2 hurricane by Tuesday.
Tropical Storm Igor
The aptly named Tropical Storm Igor has a projected path to approach the East Coast of the U.S. in mid-September, but its still too early to predict whether it will make landfall or run up the coast like Hurricane Earl.
Tropical Storm Igor projected path
The National Hurricane Center computer models for TS Igor below vary wildly at this point, showing just how hard it is to predict too far in advance exactly where these big storms will go.
NHC computer models for Igor
We’ll keep you updated with the latest projected storm path for Hurricane Igor as it draws nearer our shores.
And that’s the latest from Action News on Tropical Storm Igor.
Tags: computer models, hurricane igor, hurricane igor path, Latest updates, national hurricane center, Tropical Storm Igor
September 10th, 2010 at 3:08 pm
TROPICAL STORM IGOR DISCUSSION NUMBER 9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
1100 AM AST FRI SEP 10 2010
IGOR REMAINS A SHEARED TROPICAL CYCLONE.
DURING THE PAST FEW HOURS…HOWEVER…THE SHEAR HAS BEGUN TO SHOW SIGNS OF ABATING AND THE LOW-LEVEL CENTER IS NOW FARTHER INTO THE EASTERN PORTION OF THE CENTRAL DEEP CONVECTION.
THE UPGRADE TO STORM STATUS IS BASED ON A SATELLITE INTENSITY ESTIMATE OF 35 KT FROM TAFB AND A 47-KT UW-CIMSS 3-HR AVERAGE ADT.
THE INITIAL MOTION IS 280/14.
THE INITIAL POSITION AND MOTION ARE STILL SOMEWHAT UNCERTAIN DUE TO MULTIPLE CIRCULATIONS ROTATING AROUND THE CENTER OF A LARGER CYCLONIC GYRE.
HOWEVER…THE MOTION IS EXPECTED TO BE BASICALLY WESTWARD FOR THE NEXT 96 HOURS OR SO ALONG THE SOUTHERN PERIPHERY OF A STRONG SUBTROPICAL RIDGE LOCATED TO THE NORTH OF THE CYCLONE.
BY DAY 5…A SERIES OF WEAK SHORTWAVE TROUGHS MOVING THROUGH THE BASE OF A BROAD LONGWAVE TROUGH FORECAST TO BE OFF THE U.S. EAST COAST IS FORECAST BY ALL OF THE GLOBAL MODELS TO CREATE A WEAKNESS IN THE RIDGE BETWEEN 50W-60W LONGITUDE.
THIS IS EXPECTED TO WEAKEN THE STEERING FLOW AND CAUSE IGOR TO SLOW DOWN AND ALSO TURN WEST-NORTHWESTWARD.
THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND THE TVCN MODEL CONSENSUS.
CURRENT SHEAR ANALYSES FROM SHIPS AND UW-CIMSS…ALONG WITH WATER VAPOR WINDS…INDICATE THE VERTICAL SHEAR ACROSS IGOR HAS DECREASED FROM 20 KT DOWN TO 10 KT DURING THE PAST 24 HOURS.
THIS DECEASING SHEAR TENDENCY IS EXPECTED TO CONTINUE THROUGHOUT THE FORECAST PERIOD AS IGOR MOVES OVER GRADUALLY INCREASING SSTS…ESPECIALLY AFTER 48 HOURS.
THE RESULT SHOULD BE STEADY INTENSIFICATION WITH IGOR POSSIBLY REACHING HURRICANE STATUS ON SUNDAY AND MAJOR HURRICANE STATUS BY DAY 5…AS INDICATED BY THE SHIPS…GFDL…AND HWRF MODELS.
THE OFFICIAL INTENSITY FORECAST IS A LITTLE BELOW THE GUIDANCE THROUGH 48 HOURS DUE TO UNCERTAINTY ABOUT WHEN IGOR WILL DEVELOP A CONSOLIDATED CENTER OF CIRCULATION…BUT IS CLOSE TO THE GUIDANCE THEREAFTER.
TROPICAL STORM FORECAST POSITIONS AND MAX WINDS
INITIAL 10/1500Z 16.4N 31.0W 35 KT
12HR VT 11/0000Z 16.6N 33.2W 40 KT
24HR VT 11/1200Z 16.8N 36.2W 45 KT
36HR VT 12/0000Z 17.0N 39.2W 50 KT
48HR VT 12/1200Z 17.1N 41.7W 60 KT
72HR VT 13/1200Z 17.3N 46.2W 70 KT
96HR VT 14/1200Z 18.2N 50.3W 85 KT
120HR VT 15/1200Z 19.5N 53.5W 95 KT
September 10th, 2010 at 11:34 pm
TROPICAL STORM IGOR DISCUSSION NUMBER 11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
1100 PM AST FRI SEP 10 2010
CONVENTIONAL SATELLITE IMAGES INDICATE THAT IGOR IS MAINTAINING A BURSTING PATTERN…CHARACTERISTIC OF A SHEARED TROPICAL CYCLONE.
THE PARTIALLY EXPOSED LOW-LEVEL CENTER LIES NEAR THE NORTHEAST SIDE OF A LARGE AND CIRCULAR CONVECTIVE MASS IN THIS IMAGERY…BUT SEVERAL EARLIER MICROWAVE OVERPASSES INDICATED THE POSSIBILITY OF THE LOW-LEVEL CENTER LYING UNDERNEATH THE CONVECTION.
AN EXPANDING UPPER-LEVEL OUTFLOW IS WELL ESTABLISHED IN ALL QUADRANTS EXCEPT TO THE EAST.
DVORAK INTENSITY ESTIMATES ARE AT 3.0/45 KT AND 3.5/55 KT FROM SAB AND TAFB…AND THE LATEST 3-HOURLY AVERAGED ADT VALUE IS 3.3.
GIVEN THE UNCERTAINTY WITH REGARD TO THE LOCATION OF THE CENTER…THE ADVISORY INTENSITY IS INCREASED CONSERVATIVELY TO 45 KT.
THE INITIAL MOTION ESTIMATE OF 285/18 IS SOMEWHAT UNCERTAIN AND REPRESENTS A LONGER-TERM AVERAGE…GIVEN DIFFERENCES BETWEEN CONVENTIONAL AND MICROWAVE SATELLITE FIXES.
THE FORECAST REASONING REMAINS UNCHANGED.
DYNAMICAL MODELS SHOW IGOR MOVING ON A WESTWARD COURSE ON THE SOUTH SIDE OF A SUBTROPICAL RIDGE OVER THE EAST CENTRAL ATLANTIC DURING THE NEXT 72 HOURS.
DURING THIS PERIOD…THE MODEL GUIDANCE IS IN GOOD AGREEMENT THAT IGOR SHOULD SLOW ITS FORWARD SPEED AND THEN TURN WEST-NORTHWESTWARD BEYOND 72 HOURS IN RESPONSE TO A LARGE BREAK IN THE SUBTROPICAL RIDGE OVER THE WESTERN AND CENTRAL ATLANTIC.
THE OFFICIAL NHC TRACK LIES NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE…BUT IS A BIT NORTH OF THE MULTI-MODEL CONSENSUS WHICH HAS TRENDED SLIGHTLY SOUTHWARD THIS CYCLE.
UW-CIMSS ANALYSES STILL INDICATE AROUND 15 KT OF NORTHEASTERLY VERTICAL WIND SHEAR OVER IGOR…A LESS THAN IDEAL ENVIRONMENT FOR INTENSIFICATION.
THE STATISTICAL-DYNAMICAL GUIDANCE INDICATES A QUICK REDUCTION TO THE SHEAR DURING THE NEXT 24 HOURS…AND A LOW SHEAR ENVIRONMENT OVER GRADUALLY WARMER WATERS ARE LIKELY TO LEAD TO A STEADIER STRENGTHENING OVER THE NEXT COUPLE OF DAYS.
THE INTENSITY GUIDANCE PRESENTS A DILEMMA LATER IN THE FORECAST PERIOD…HOWEVER.
THE STATISTICAL MODEL OUTPUT INDICATES POSSIBLE SOUTHWESTERLY SHEAR RELATED TO THE LONGWAVE TROUGH FORECAST OVER THE WEST CENTRAL ATLANTIC…AS DO A FEW OF THE GLOBAL DYNAMICAL MODELS.
ON THE OTHER HAND…THE HWRF AND ECMWF SOLUTIONS A CONTINUATION OF THE LOW SHEAR ENVIRONMENT AND A STRONGER IGOR.
THE OFFICIAL NHC INTENSITY FORECAST IS ABOUT THE SAME AS THE PREVIOUS ONE…EXCEPT SLIGHTLY REDUCED LATE IN THE PERIOD IN DEFERENCE TO THE STATISTICAL MODELS.
TROPICAL STORM IGOR FORECAST POSITIONS AND MAX WINDS
INITIAL 11/0300Z 17.1N 34.9W 45 KT
12HR VT 11/1200Z 17.2N 37.2W 50 KT
24HR VT 12/0000Z 17.4N 40.1W 55 KT
36HR VT 12/1200Z 17.5N 42.8W 65 KT
48HR VT 13/0000Z 17.6N 45.3W 75 KT
72HR VT 14/0000Z 18.0N 49.5W 85 KT
96HR VT 15/0000Z 19.0N 53.0W 90 KT
120HR VT 16/0000Z 20.5N 56.0W 100 KT
September 11th, 2010 at 9:46 am
Hurricane Igor On Its Way
TROPICAL STORM IGOR DISCUSSION NUMBER 12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
500 AM AST SAT SEP 11 2010
IGOR IS STRENGTHENING AND IN FACT…THERE WAS A PERIOD FOR ABOUT TWO HOURS…BETWEEN 04 AND 06 UTC THAT A SMALL EYE-LIKE FEATURE BECAME APPARENT ON SATELLITE. HOWEVER…SINCE THEN…SUCH FEATURE HAS BECOME INTERMITTENT…OTHERWISE I COULD HAVE DECLARED IGOR A HURRICANE.
ALTHOUGH THE CLOUD PATTERN IS BETTER ORGANIZED…THE OVERALL CONVECTION HAS DECREASED A LITTLE AND NOW CONSISTS OF TWO WELL-DEFINED CYCLONICALLY CURVED BANDS LOCATED PRIMARILY TO THE SOUTH OF THE CENTER. THE OUTFLOW HAS BECOME ESTABLISHED IN ALL QUADRANTS.
BASED ON A BLEND OF T-NUMBERS FROM TAFB AND SAB WHICH ARE 4.0 AND 3.5 ON THE DVORAK SCALE…THE INITIAL INTENSITY HAS BEEN INCREASED TO 60 KNOTS.
GIVEN THE CURRENT INTENSITY TREND…THE CYCLONE WILL LIKELY BECOME A HURRICANE LATER TODAY.
ALL OF THE ENVIRONMENTAL PARAMETERS APPEAR TO BE FAVORABLE FOR IGOR TO INTENSIFY…AND THE FORECAST CALLS FOR IGOR TO BE AN INTENSE HURRICANE IN ABOUT 3 DAYS.
GLOBAL MODELS SUGGEST THAT IGOR COULD ALSO BECOME LARGE.
IGOR IS MOVING TOWARD TOWARD THE WEST OR 270 DEGREES AT 18 KNOTS.
THIS IS BASED ON THE MOTION OF THE EYE-LIKE FEATURE AND CONTINUITY.
THE CYCLONE IS BEING STEERED BY A BUILDING SUBTROPICAL RIDGE OVER THE EASTERN ATLANTIC…AND THIS PATTERN IS FORECAST BY GLOBAL MODELS TO PERSIST. ON THIS BASIS…THE OFFICIAL FORECAST CALLS FOR A GENERAL WESTWARD MOTION FOR THE NEXT 3 DAYS OR SO.
BY THEN…IGOR WILL BE REACHING THE SOUTHWESTERN EDGE OF THE SUBTROPICAL HIGH WHERE THE STEERING CURRENTS ARE WEAKER…AND BEGIN TO APPROACH A BROAD TROUGH OVER THE WESTERN ATLANTIC.
THIS PATTERN SHOULD FORCE IGOR TO SLOW DOWN AND BEGIN TO TURN MORE TO THE WEST-NORTHWEST AND NORTHWEST.
THE TRACK FORECAST IS VERY CLOSE TO THE CONSENSUS AND BIASED TO THE ECMWF AND THE GFS.
HURRICANE IGOR FORECAST POSITIONS AND MAX WINDS
INITIAL 11/0900Z 17.1N 37.8W 60 KT
12HR VT 11/1800Z 17.1N 40.2W 70 KT
24HR VT 12/0600Z 17.2N 43.1W 75 KT
36HR VT 12/1800Z 17.4N 46.0W 80 KT
48HR VT 13/0600Z 17.5N 48.5W 90 KT
72HR VT 14/0600Z 17.5N 52.5W 100 KT
96HR VT 15/0600Z 18.5N 55.5W 100 KT
120HR VT 16/0600Z 20.5N 59.0W 100 KT
September 11th, 2010 at 6:10 pm
TROPICAL STORM IGOR DISCUSSION NUMBER 14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
500 PM AST SAT SEP 11 2010
IGOR IS VERY CLOSE TO BECOMING A HURRICANE.
SATELLITE IMAGES SHOW THAT CONVECTION HAS INCREASED AROUND THE CENTER AND HAVE RECENTLY SUGGESTED THAT AN EYEWALL COULD BE FORMING.
ALTHOUGH MOST OF THE INTENSITY ESTIMATION TECHNIQUES SUGGEST IGOR IS A HURRICANE…IT IS PREFERABLE TO WAIT AND SEE IF THE CONVECTION STICKS AROUND AND TO GET MICROWAVE CONFIRMATION OF THE INNER CORE STRUCTURE.
MOST OF THE ENVIRONMENTAL FACTORS NEAR THE CYCLONE SEEM RATHER CONDUCIVE FOR STRENGTHENING.
GLOBAL MODELS ALL BUILD AN UPPER ANTICYCLONE JUST TO THE NORTH OF IGOR…A RATHER FAVORABLE PATTERN FOR THE DEVELOPMENT OF A MAJOR HURRICANE.
SSTS AND OCEAN HEAT CONTENT ALSO INCREASE STEADILY ALONG THE FORECAST TRACK.
THE MOST OBVIOUS INHIBITING FACTOR IS PERHAPS A WEDGE OF DRIER AIR THAT HAS WORKED ITS WAY INTO THE NORTHERN PART OF THE CIRCULATION.
HOWEVER…THAT DRY AIR PROBABLY WILL NOT BE ABLE TO MAKE IT INTO THE INNER CORE WITHOUT SOME SHEAR…AND THAT DOES NOT SEEM LIKELY AT THIS TIME.
THUS…THE INTENSITY FORECAST IS RAISED FROM THE PREVIOUS ONE…BUT PEAKS BELOW THE LGEM AND SHIPS MODELS.
IT IS OF NOTE THAT ALL OF THE GLOBAL MODELS SHOW THE DEVELOPMENT OF A LARGE AND POWERFUL HURRICANE…AND THE FORECAST WIND RADII HAVE BEEN INCREASED.
IGOR REMAINS ON TRACK AND IS MOVING 275/16.
THE SYNOPTIC STEERING FOR THE NEXT SEVERAL DAYS APPEARS WELL DEFINED WITH A RIDGE TO THE NORTH OF THE TROPICAL CYCLONE GUIDING THE CYCLONE GENERALLY WESTWARD.
HOWEVER…THE STRENGTH OF THIS RIDGE IS CRITICAL TO WHEN IGOR BEGINS A MORE WEST-NORTHWEST MOTION.
THE MODELS THAT MOVE THE STORM FASTER TO THE WEST INITIALLY…SUCH AS THE NOGAPS OR UKMET…ALLOW IGOR TO GET A LITTLE CLOSER TO THE NORTHERN LEEWARD ISLANDS BEFORE MAKING A WEST-NORTHWEST TURN IN TWO OR THREE DAYS.
HOWEVER…ANOTHER GROUP OF MODELS…INCLUDING THE GFS/GFDL SOLUTIONS…SHOW THAT TURN OCCURRING IN THE NEXT DAY OR TWO.
THE MODEL SPREAD HAS INCREASED SINCE THE LAST ADVISORY…AND I HAVE ELECTED NOT TO CHANGE THE FORECAST MUCH…WHICH REMAINS TO THE SOUTH AND WEST OF THE DYNAMICAL MODEL CONSENSUS FOR NOW.
HURRICANE IGOR FORECAST POSITIONS AND MAX WINDS
INITIAL 11/2100Z 17.4N 41.2W 60 KT
12HR VT 12/0600Z 17.5N 43.6W 70 KT
24HR VT 12/1800Z 17.6N 46.4W 80 KT
36HR VT 13/0600Z 17.7N 48.8W 90 KT
48HR VT 13/1800Z 17.9N 51.0W 100 KT
72HR VT 14/1800Z 18.8N 54.8W 115 KT
96HR VT 15/1800Z 20.3N 57.7W 115 KT
120HR VT 16/1800Z 22.0N 60.5W 115 KT
September 12th, 2010 at 9:59 am
HURRICANE IGOR DISCUSSION NUMBER 16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
500 AM AST SUN SEP 12 2010
SATELLITE IMAGES SUGGEST THAT IGOR HAS STRENGTHENED A LITTLE MORE THIS MORNING.
ALTHOUGH DVORAK CLASSIFICATIONS WERE 65 KT FROM BOTH TAFB AND SAB AT 0600 UTC…THE CURVED BAND OVER THE EASTERN SEMICIRCLE HAS BECOME BETTER DEFINED AND THE OVERALL CLOUD PATTERN IS NOW MORE SYMMETRIC.
THEREFORE…THE INITIAL INTENSITY IS RAISED TO 70 KT FOR THIS ADVISORY…WHICH IS IN AGREEMENT WITH THE ADT ESTIMATES.
CONDITIONS APPEAR FAVORABLE FOR ADDITIONAL STRENGTHENING DURING THE NEXT FEW DAYS AS IGOR MOVES OVER STEADILY INCREASING SEA SURFACE TEMPERATURES AND REMAINS IN A LOW WIND SHEAR ENVIRONMENT.
MOST OF THE INTENSITY MODELS BRING IGOR TO MAJOR HURRICANE STATUS WITHIN A COUPLE OF DAYS…AND THE OFFICIAL FORECAST FOLLOWS THIS GUIDANCE.
BEYOND A FEW DAYS…THE MODELS ARE MIXED WITH SOME SHOWING LITTLE CHANGE IN STRENGTH AND OTHERS GRADUAL WEAKENING.
THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ONE…AND CLOSER TO THE LGEM AND SHIPS MODELS…PREDICTING IGOR TO MAINTAIN MAJOR HURRICANE STATUS.
IGOR CONTINUES TO MOVE WESTWARD ABOUT THE SAME SPEED AS ESTIMATED EARLIER…275/16.
A SUBTROPICAL RIDGE LOCATED TO THE NORTH OF THE HURRICANE IS EXPECTED TO KEEP IGOR ON A WESTWARD TRACK FOR THE NEXT 2 TO 3 DAYS.
THEREAFTER…THE GLOBAL MODELS ARE IN AGREEMENT IN SHOWING THE RIDGE ERODE DUE TO PERSISTENT BROAD TROUGHING OVER THE WESTERN ATLANTIC.
THIS FLOW PATTERN SHOULD ALLOW IGOR TO TURN WEST-NORTHWESTWARD TO NORTHWESTWARD DURING THAT TIME PERIOD.
THE MODEL GUIDANCE HAS NOT CHANGED MUCH FROM THE LAST CYCLE…AND THE OFFICIAL FORECAST IS GENERALLY AN UPDATE OF THE PREVIOUS ONE.
HURRICANE IGOR FORECAST POSITIONS AND MAX WINDS
INITIAL 12/0900Z 17.7N 44.4W 70 KT
12HR VT 12/1800Z 17.9N 46.5W 75 KT
24HR VT 13/0600Z 18.1N 49.1W 80 KT
36HR VT 13/1800Z 18.3N 51.3W 90 KT
48HR VT 14/0600Z 18.7N 53.2W 100 KT
72HR VT 15/0600Z 20.2N 56.3W 115 KT
96HR VT 16/0600Z 22.5N 59.0W 115 KT
120HR VT 17/0600Z 24.5N 62.0W 115 KT
September 12th, 2010 at 5:32 pm
Hurricane Igor Now A Monster Category 4 Storm
HURRICANE IGOR DISCUSSION NUMBER 19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
500 PM AST SUN SEP 12 2010
IGOR CONTINUES TO INTENSIFY AT A RAPID PACE.
DVORAK INTENSITY ESTIMATES AND THE UW-CIMSS ADT HAVE INCREASED FURTHER…AND THE INITIAL INTENSITY IS ADJUSTED SLIGHTLY UPWARD TO 120 KT BASED ON A COMPROMISE OF THESE DATA AND THE LATEST SATCON INTENSITY ESTIMATE.
THE OFFICIAL INTENSITY FORECAST HAS ALSO BEEN ADJUSTED TO SHOW SOME FURTHER STRENGTHENING AND A PEAK INTENSITY AT DAY 3 OF 135 KT…SIMILAR TO SHIPS MODEL.
FOR THE REMAINDER OF THE PERIOD…THE OFFICIAL FORECAST CALLS FOR SOME GRADUAL WEAKENING AND IS BASED PRIMARILY ON THE ICON CONSENSUS MODEL.
IT IS WORTH NOTING THAT FLUCTUATIONS IN STRENGTH DUE TO EYEWALL REPLACEMENT CYCLES ARE POSSIBLE…HOWEVER…THERE IS LITTLE SKILL IN FORECASTING THE TIMING OF THESE CYCLES.
THE INITIAL MOTION ESTIMATE REMAINS 270/12.
THE TRACK FORECAST PHILOSOPHY REMAINS UNCHANGED FOR THIS ADVISORY…HOWEVER THERE IS STILL CONSIDERABLE DYNAMICAL MODEL SPREAD AFTER 36 HOURS.
THE HWRF…UKMET AND ECMWF REMAIN TO THE LEFT OF THE CONSENSUS AND ARE SLIGHTLY SLOWER…WHILE THE OTHER REGIONAL AND GLOBAL MODELS SUGGEST A MORE PRONOUNCED WEAKNESS WITH TIME IN THE MID- TO UPPER-LEVEL RIDGE.
THE NHC TRACK FORECAST IS NUDGED TO THE RIGHT OF THE PREVIOUS FORECAST AFTER DAY 3…CLOSER TO THE TVCN CONSENSUS MODEL…BUT STILL TO THE LEFT OUT OF RESPECT TO THE RELIABLE ECMWF MODEL.
LATEST UPDATE ON HURRICANE IGOR – FORECAST POSITIONS AND MAX WINDS
INITIAL 12/2100Z 17.7N 46.9W 120 KT
12HR VT 13/0600Z 17.8N 48.7W 125 KT
24HR VT 13/1800Z 18.1N 50.8W 125 KT
36HR VT 14/0600Z 18.7N 52.6W 130 KT
48HR VT 14/1800Z 19.4N 54.3W 130 KT
72HR VT 15/1800Z 21.3N 57.1W 135 KT
96HR VT 16/1800Z 23.5N 60.0W 125 KT
120HR VT 17/1800Z 25.8N 62.9W 120 KT
September 13th, 2010 at 1:54 pm
HURRICANE IGOR DISCUSSION NUMBER 22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
1100 AM AST MON SEP 13 2010
IGOR CONTINUES TO HAVE A DISTINCT EYE SURROUNDED BY TOPS OF -60C TO -70C.
DVORAK CLASSIFICATIONS FROM TAFB AND SAB WERE 6.5…AND THE INITIAL INTENSITY REMAINS 130 KT.
THE UW-CIMSS SECONDARY EYEWALL FORMATION INDEX STRONGLY SUGGESTS THAT A SECONDARY EYEWALL WILL FORM IN THE NEXT DAY OR TWO…AND THIS WILL LIKELY RESULT IN SOME SHORT TERM INTENSITY FLUCTUATIONS THAT ARE NOT REPRESENTED IN THE OFFICIAL FORECAST.
ON LONGER TIME SCALES…ALL OF THE INTENSITY GUIDANCE SUGGESTS THAT IGOR IS NEAR PEAK INTENSITY…AND SHOW GRADUAL WEAKENING THROUGH THE PERIOD.
HOWEVER…SINCE THE CYCLONE REMAINS IN WHAT APPEARS TO BE AN IDEAL ENVIRONMENT FOR THE NEXT 72 HOURS…THE OFFICIAL FORECAST IS ADJUSTED ONLY SLIGHTLY DOWNWARD THROUGH THAT TIME.
AT DAYS 4 AND 5…VERTICAL SHEAR MAY BEGIN TO INCREASE OVER THE HURRICANE…HOWEVER…THIS INCREASE WILL BE SENSITIVE TO THE VERY UNCERTAIN TRACK FORECAST AT THOSE TIME RANGES.
THEREFORE…AT THOSE TIMES THE OFFICIAL FORECAST IS CLOSE TO OR A LITTLE ABOVE THE STRONGEST MODEL…THE SHIPS.
THE INITIAL MOTION ESTIMATE IS 265/9 KNOTS…A LITTLE SLOWER THAN BEFORE…AND A BIT SOUTH OF THE PREVIOUS FORECAST.
MOST OF THE GUIDANCE…WITH THE EXCEPTION OF THE UKMET…SHOWS IGOR TURNING TOWARD THE WEST-NORTHWEST BY TONIGHT AND THEN TURNING NORTHWESTWARD BY 48 HOURS AS IT MOVES INTO A LARGE BREAK IN THE SUBTROPICAL RIDGE.
THE OFFICIAL FORECAST IS A LITTLE SOUTH OF THE PREVIOUS ONE THROUGH 12 HOURS GIVEN THE INITIAL POSITION AND MOTION.
FROM 12 THROUGH 48 HOURS THE OFFICIAL FORECAST IS SIMILAR TO BUT A LITTLE SLOWER THAN THE PREVIOUS PACKAGE AND TRENDS TOWARD THE TVCN CONSENSUS MODEL FORWARD SPEED.
AT 72 HOURS AND BEYOND THERE IS CONSIDERABLE UNCERTAINTY WITH THE EVOLUTION OF THE LARGE-SCALE FLOW AND THE TRACK OF IGOR.
THE ECMWF AND UKMET SHOW MORE MID-LEVEL RIDGING NORTH AND NORTHEAST OF IGOR OVER THE CENTRAL ATLANTIC AND MOVE IGOR SLOWER AND FARTHER SOUTH THAN THE REST OF THE GUIDANCE AT DAYS 3 THROUGH 5.
THE GFS…GFDL…AND GFDN KEEP THIS RIDGE FARTHER EAST AND ALLOW IGOR TO GAIN MORE LATITUDE AND RECURVE AHEAD OF A LONGWAVE TROUGH SITUATED OFFSHORE OF THE NORTHEASTERN UNITED STATES.
THE NOGAPS AND HWRF ARE BETWEEN THESE TWO CAMPS AND SHOW A NORTHWESTWARD MOTION AT DAY 5.
GIVEN THE INCREASING SPREAD OF THE GUIDANCE LATE IN THE PERIOD…THE OFFICIAL FORECAST IS SIMPLY AN UPDATE OF THE PREVIOUS ADVISORY AT THESE TIMES AND IS OF LOWER CONFIDENCE THAN NORMAL.
THE NHC TRACK IS CLOSE TO THE NOGAPS AND WELL TO THE NORTH OF THE UKMET AND ECMWF AT THE END OF THE PERIOD.
HURRICANE IGOR FORECAST POSITIONS AND MAX WINDS
INITIAL 13/1500Z 17.5N 49.7W 130 KT
12HR VT 14/0000Z 17.9N 50.8W 135 KT
24HR VT 14/1200Z 18.7N 52.3W 130 KT
36HR VT 15/0000Z 19.5N 53.7W 130 KT
48HR VT 15/1200Z 20.6N 55.2W 125 KT
72HR VT 16/1200Z 23.0N 58.0W 115 KT
96HR VT 17/1200Z 25.5N 60.5W 110 KT
120HR VT 18/1200Z 29.0N 63.5W 100 KT
September 13th, 2010 at 8:45 pm
HURRICANE IGOR DISCUSSION NUMBER 23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
500 PM AST MON SEP 13 2010
THE STRUCTURE OF IGOR HAS CHANGED LITTLE OVER THE PAST FEW HOURS.
THE EYE REMAINS VERY DISTINCT IN IR AND VISIBLE IMAGERY…AND ALTHOUGH THE TOPS SURROUNDING THE EYE HAVE WARMED A BIT…DVORAK CLASSIFICATIONS STILL SUPPORT AN INTENSITY OF 130 KT.
IGOR WILL REMAIN IN A FAVORABLE ENVIRONMENT FOR MAINTAINING ITS CURRENT INTENSITY FOR THE NEXT COUPLE OF DAYS…AND THE OFFICIAL FORECAST DOES NOT SHOW ANY WEAKENING UNTIL AFTER 48 HOURS.
WHILE A 1640 UTC AMSR-E PASS DOES NOT SHOW ANY EVIDENCE OF A SECONDARY EYEWALL YET…IT IS POSSIBLE THAT AN EYEWALL REPLACEMENT CYCLE WILL OCCUR IN THE FIRST COUPLE OF DAYS…WHICH COULD RESULT IN SOME INTENSITY FLUCTUATIONS NOT REPRESENTED IN THE OFFICIAL FORECAST.
BEYOND 36 HOURS…ALL OF THE INTENSITY GUIDANCE SUGGEST THAT SLOW WEAKENING SHOULD BEGIN…ALTHOUGH THERE ARE NO OVERLY NEGATIVE FACTORS UNTIL THE VERY END OF THE PERIOD WHEN THE VERTICAL SHEAR MAY INCREASE.
THE OFFICIAL FORECAST SHOWS A GRADUAL WEAKENING AT DAYS 3 THROUGH 5 BUT IS HIGHER THAN MOST OF THE GUIDANCE THROUGH THE PERIOD.
THE INITIAL MOTION IS STILL DUE WEST…270 DEGREES…AT 9 KNOTS.
ALL OF THE GUIDANCE…EXCEPT THE UKMET…INSISTS ON A TURN TOWARD THE WEST-NORTHWEST IN THE NEXT 12 HOURS AS IGOR BEGINS TO MOVE INTO A LARGE WEAKNESS IN THE SUBTROPICAL RIDGE.
HOWEVER…DUE TO THE INITIAL POSITION AND MOTION…THE OFFICIAL FORECAST HAS AGAIN BEEN ADJUSTED A LITTLE TO THE LEFT OF THE PREVIOUS ADVISORY THROUGH 48 HOURS.
BEYOND THAT TIME…THERE IS STILL SOME SPREAD IN THE TRACK GUIDANCE.
THE ECMWF AND UKMET STILL SHOW A STRONGER RIDGE NORTH OF IGOR THROUGH MUCH OF THE PERIOD…TAKING THE CYCLONE FARTHER WEST THAN THE REST OF THE GUIDANCE.
THE GFS AND GFDL CONTINUE TO SHOW THE LEAST RIDGING AND TURN IGOR NORTH-NORTHWESTWARD AT THE END OF THE PERIOD AHEAD OF A MID-LATITUDE TROUGH.
WHILE CONFIDENCE IN THE TRACK FORECAST LATE IN THE PERIOD REMAINS LOW…THE GUIDANCE SHOWS A LITTLE LESS SPREAD NOW THAN EARLIER TODAY.
THE NEW OFFICIAL FORECAST SHOWS A NORTHWESTWARD MOTION AT DAYS 3 THROUGH 5…AND IS SIMILAR TO THE PREVIOUS FORECAST.
THIS ENDS UP BEING VERY CLOSE TO THE TVCN MULTI-MODEL CONSENSUS AND A BLEND OF THE GFS AND ECMWF MODELS.
LARGE SWELLS FROM IGOR WILL BEGIN AFFECTING THE LEEWARD ISLANDS TOMORROW AND REACH PUERTO RICO AND THE VIRGIN ISLANDS BY WEDNESDAY.
FORECAST POSITIONS AND MAX WINDS
INITIAL 13/2100Z 17.7N 50.5W 130 KT
12HR VT 14/0600Z 18.1N 51.7W 130 KT
24HR VT 14/1800Z 18.9N 53.2W 130 KT
36HR VT 15/0600Z 20.0N 54.7W 130 KT
48HR VT 15/1800Z 21.1N 56.1W 130 KT
72HR VT 16/1800Z 23.5N 58.5W 120 KT
96HR VT 17/1800Z 26.5N 61.5W 110 KT
120HR VT 18/1800Z 30.0N 64.0W 105 KT