TROPICAL CYCLONE 01B (MAHASEN), LOCATED APPROXIMATELY 760 NM SOUTH
OF CALCUTTA, INDIA, HAS TRACKED NORTHWESTWARD AT 12 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
REVEALS FLARING DEEP CENTRAL CONVECTION WITH FRAGMENTED CONVECTIVE
BANDING WRAPPING INTO A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER
(LLCC) WITH SEVERAL LARGE OUTFLOW BOUNDARIES APPARENT IN THE EASTERN
AND SOUTHERN SEMI-CIRCLES. THIS IS ALSO APPARENT IN A 120342Z AMSU-B
MICROWAVE IMAGE. THE PAST FEW MICROWAVE IMAGES HAVE SHOWN A RE-
CONSOLIDATION OF THE LLCC FURTHER EAST OF THE PREVIOUS POSITION AND
HAVE ADDITIONALLY SHOWN DRY CONTINENTAL AIR IS BEING INGESTED FROM
THE COAST OF INDIA. THIS CAN ALSO BE SEEN IN THE LATEST MICROWAVE
DERIVED TOTAL PRECIPITABLE WATER LOOP. OBSERVATIONS IN KOLKATA,
INDIA SHOW A LARGE DEW POINT SPREAD OF 20 DEGREES. THIS DRY AIR
INGESTION IS REASON FOR THE FRAGMENTED AND FLARING NATURE OF THE
SYSTEM OVER THE LAST 12 HOURS. THE INITIAL POSITION IS BASED UPON
THE MSI LOOP AND EXTRAPOLATION FROM THE 120342Z AMSU IMAGE WITH LOW
CONFIDENCE. THE INITIAL INTENSITY HAS BEEN SLIGHTLY LOWERED TO 45
KNOTS BASED ON LOWER DVORAK INTENSITY ESTIMATES FROM ALL AGENCIES
AND THE OVERALL CONVECTIVE ORGANIZATION OF THE SYSTEM. UPPER-LEVEL
ANALYSIS REVEALS A FAVORABLE ENVIRONMENT OF STRONG DIFFLUENCE ALOFT
PROVIDING FAVORABLE OUTFLOW AND LOW TO MODERATE VERTICAL WIND SHEAR
(VWS), WHICH IS BEING OFFSET BY THE STORM MOTION, RESULTING IN AN
OVERALL LOW VWS (05-10 KNOTS) ENVIRONMENT. TC 01B IS FORECAST TO
CONTINUE NORTHWESTWARD FOR THE NEXT 12 HOURS ALONG THE SOUTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE (STR) SITUATED OVER THE NORTHERN
ANDAMAN SEA. AFTER TAU 12, IT IS EXPECTED TO SLOW DOWN BEFORE IT
TURNS NORTHEASTWARD AS THE STR WEAKENS AND RE-ORIENTS IN RESPONSE TO
AN APPROACHING MID-LATITUDE SHORTWAVE TROUGH CURRENTLY OVER NORTHERN
INDIA. TC 01B WILL CONTINUE TO INTENSIFY TO A PEAK OF 80 KNOTS BY
TAU 72 AS THE SYSTEM CROSSES THE RIDGE AXIS INTO AN AREA OF
INCREASED POLEWARD OUTFLOW, WITH ITS EXPOSURE INTO THE STRONG
WESTERLIES. AFTER TAU 96, THE SYSTEM WILL MAKE LANDFALL NEAR
CHITTAGONG, BANGLADESH, AS A SIGNIFICANT CYCLONE ALL WHILE WEAKENING
DUE TO THE LAND INTERACTION. DYNAMIC MODEL GUIDANCE HAS DEVELOPED A
BIFURCATION IN THE LATEST RUN AS GFDN AND NAVGEM HAVE GREATLY
DEVIATED TO THE NORTHWEST INTO NORTHEASTERN INDIA. THIS IS BELIEVED
TO BE DUE TO THE MODEL TRACKERS ERRONEOUSLY TRACKING INTO THE
PREVIOUSLY MENTIONED SHORTWAVE TROUGH. GFS, ECMWF AND EGRR HAVE
STAYED CONSISTENT WITH THE RECURVE SCENARIO INTO BANGLADESH. DUE TO
THIS, THE JTWC FORECAST IS FASTER AND EAST OF MULTI-MODEL CONSENSUS
TO OFFSET THE NAVGEM AND GFDN SOLUTIONS AND IS CONSISTENT WITH THE
PREVIOUS FORECAST. DUE TO LARGE SPREAD IN THE MODEL SOLUTIONS AND
AMBIGUITY IN THE INITIAL POSITION FORECAST CONFIDENCE IS LOW.
JUSTIFICATION FOR RELOCATION: RELOCATED 12/00Z POSITION OF TC 01B
BASED ON NEWLY AVAILABLE MICROWAVE DATA. MAXIMUM SIGNIFICANT WAVE
HEIGHT AT 120600Z IS 18 FEET.
~~~~~~~~~~~~~~~~~~~~~~~~~~~
The cyclonic storm MAHASEN over southeast Bay of Bengal moved slightly
westwards at a speed of 15kmph and lay centred at 1130 hrs IST of 12th May 2013 near latitude 10.00 N and longitude 87.00 E, about 650 km west-northwest of Car Nicobar, 650 km east-northeast of Trincomalee, 800 km southeast of Chennai and 1440 km south-southwest of Chittagong. It would move initially northwestwards during next 36 hours and recurve thereafter northeastwards towards Bangladesh-Myanmar coast.
Latest NAVGEM (NOGAPS) model expects a N-E Andhra and S.Odisha coast landfall on 16-May.
TROPICAL CYCLONE 01B (MAHASEN), LOCATED APPROXIMATELY 749 NM
SOUTHWARD OF CALCUTTA, INDIA, HAS TRACKED NORTHWESTWARD AT 15
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS THE LARGE CENTRAL DENSE OVERCAST FEATURE THAT WAS
OBSCURING THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS BROKEN UP AND
MERGED INTO THE CONVECTIVE BANDS FEEDING INTO THE LLCC. ALTHOUGH THE
CONVECTION HAS BECOME FRAGMENTED, THE FEEDER BANDS HAVE WRAPPED
TIGHTER INTO THE LLCC. THE INITIAL POSITION IS BASED ON THE ABOVE
ANIMATION AND FROM A NOTCH FEATURE ON AN 112159Z TRMM MICROWAVE IMAGE
WITH FAIR CONFIDENCE. THE INITIAL INTENSITY IS MAINTAINED AT 50
KNOTS. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM IS 05 DEGREES SOUTH
OF THE RIDGE AXIS IN AN AREA OF LOW (05-10 KNOT) VERTICAL WIND SHEAR
(VWS) AND EXCELLENT RADIAL OUTFLOW. TC 01B IS FORECAST TO CONTINUE
NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE (STR). AFTER TAU 12, IT IS EXPECTED TO SLOW DOWN BEFORE IT
TURNS NORTHEASTWARD AS THE STR WEAKENS IN RESPONSE TO AN APPROACHING
MID-LATITUDE SHORTWAVE TROUGH CURRENTLY OVER NORTHERN INDIA. TC 01B
WILL CONTINUE TO INTENSIFY TO A PEAK OF 85 KNOTS BY TAU 96 AS THE
SYSTEM CROSSES THE RIDGE AXIS INTO A ZONE OF SUSTAINED LOW VWS AND
INCREASED POLEWARD OUTFLOW WITH ITS EXPOSURE INTO THE STRONG
WESTERLIES. AFTER TAU 96, THE SYSTEM WILL MAKE LANDFALL JUST NORTH OF
CHITTAGONG, BANGLADESH, AS A MODERATE TYPHOON-STRENGTH CYCLONE.
DYNAMIC MODEL GUIDANCE IS IN BETTER AGREEMENT WITH THE RECURVE
SCENARIO TOWARDS BANGLADESH BUT WITH VARYING MODEL TRACK SPEEDS AND
MODERATE SPREADING AT THE LATER TAUS. WBAR IS ERRONEOUSLY SKEWED LEFT
OF AND MUCH SLOWER THAN THE MODEL ENVELOPE DURING THE TURN. THE JTWC
FORECAST IS POSITIONED JUST TO THE RIGHT OF THE MULTI-MODEL CONSENSUS
(CONW) DURING THE TURN AND FASTER THAN CONW AFTER THE TURN TO OFFSET
WBAR. THERE IS IMPROVED CONFIDENCE IN THE TRACK FORECAST. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 120000Z IS 18 FEET.
Monsoon - The onset of monsoon over S,S-E Bay and South Andaman islands is expected to happen today. The Northerly movement expected from "Mahasen" will make way for the strong monsoon winds to reach S.Andaman islands. Latest analysis show that strong winds are already reaching South Andamans.
Today, the Somali jet is also seen picking up strength.
TROPICAL CYCLONE 01B (MAHASEN), LOCATED APPROXIMATELY 830 NM SOUTH-
SOUTHWEST OF CHITTAGONG, BANGLADESH, HAS TRACKED NORTHWESTWARD AT 15
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) REVEALS A LARGE CENTRAL DENSE OVERCAST (CDO) FEATURE
HAS DEVELOPED OVER THE LOW-LEVEL CIRCULATION CENTER (LLCC) WITH
MULTIPLE FEEDER BANDS IN THE PERIPHERIES. AN 111140Z SSMIS 91 GHZ
MICROWAVE IMAGE SHOWS DEEP CONVECTION PERSISTING OVER THE LLCC WHILE
THE CONVECTION IN THE BANDING FEATURES REMAIN FRAGMENTED. THE
INITIAL POSITION IS BASED ON THE MICROWAVE IMAGE DUE TO THE LLCC
BEING OBSCURED BY THE LARGE CDO FEATURE WITH FAIR CONFIDENCE. THE
INITIAL INTENSITY IS ASSESSED AT 50 KNOTS, WHICH IS SLIGHTLY HIGHER
THAN CONGRUENT DVORAK INTENSITY ESTIMATES OF 45 KNOTS FROM PGTW AND
KNES, DUE TO DEEPENING CONVECTION NEAR THE LLCC. UPPER-LEVEL
ANALYSIS INDICATES A FAVORABLE ENVIRONMENT AS DIFFLUENCE ALOFT
CONTINUES TO PROVIDE FAVORABLE OUTFLOW WHILE THE CURRENT STORM
MOTION HAS BECOME IN PHASE WITH THE SOUTHEASTERLY VERTICAL WIND SHEAR
(VWS), RESULTING IN LOW (05-10 KNOTS) VWS. TC 01B IS FORECAST TO
CONTINUE NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE (STR) POSITIONED OVER THE NORTHEASTERN BAY OF
BENGAL FOR THE NEXT 24 HOURS. THEREAFTER, TC 01B IS EXPECTED TO SLOW
AND TURN NORTHEASTWARD AS THE STR WEAKENS DUE TO AN APPROACHING
MIDLATITUDE SHORTWAVE TROUGH CURRENTLY OVER NORTHERN INDIA AND THE
NORTHEASTERN ARABIAN SEA. TC 01B WILL CONTINUE TO INTENSIFY TO A
PEAK OF 85 KNOTS BY TAU 96 AS THE SYSTEM GAINS LATITUDE AND POLEWARD
OUTFLOW INCREASES INTO THE WESTERLIES. BY TAU 120 THE SYSTEM WILL
MAKE LANDFALL AS A SIGNIFICANT TC AND BEGIN TO WEAKEN DUE TO LAND
INTERACTION AND INCREASING VWS AHEAD OF THE AFOREMENTIONED SHORTWAVE
TROUGH. DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT WITH RECURVE
SCENARIO TOWARDS BANGLADESH THROUGH TAU 72, BUT TWO SEPARATE
SOLUTIONS HAVE DEVELOPED IN THE LATEST MODEL RUN PAST TAU 72.
NAVGEM, EGRR AND GFDN ACCELERATE THE SYSTEM IN THE LATER TAUS AS THE
TROUGH TRANSITS THROUGH THE AREA. GFS AND ECMWF STALL THE TROUGH
OVER NORTHEASTERN INDIA RESULTING IN A SLOWER TRACK SPEEDS. DUE TO
THIS DISAGREEMENT, THE JTWC FORECAST IS POSITIONED CLOSE TO MULTI-
MODEL CONSENSUS WHICH HEDGES BETWEEN THE TWO SEPARATE SOLUTIONS.
HIGH CONFIDENCE REMAINS IN THE FORECAST THROUGH TAU 72 DUE TO THE
TIGHT GROUPING OF THE MODELS. AFTER TAU 72, FORECAST CONFIDENCE IS
LOW DUE TO THE TWO SEPERATE SOLUTIONS OF THE MODELS. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 111200Z IS 16 FEET.
Now the COLA and NOGAPS model suggests that "Mahasen" will track N-W for one more day and then North for one day and then N-N-E.
According to COLA model the Landfall estimate is now over S.Bangladesh on 16-May.
Latest NOGAPS model suggests that the landfall may be over North Odisha coast and South Bengal coast on 16-May.
Remember, Cyclone "Laila"... same time of the year in 2010.
It also tracked the same path as that of "Mahasen" ... Laila continued to track N-W and made landfall over S.Andhra coast on 20-May-2010.
Please refer our coverage on this Cyclone here...
http://indianweatherman.blogspot.in/search?q=laila