Sunday, May 12, 2013

Cyclone "Mahasen" - Rapidly moving N-W, Now have 2 different path forecast !

Analysis show that Cyclone "Mahasen" has moved N-W during past 12hrs at a fast pace.
Latest position is 10.5N , 86.6E. (south central Bay)
No further intensification seen during past 12 hrs.
Pressure remains the same around 985 mb.
Winds gusting up to 90 kmph.

JTWC warning and path projection at 8:39am IST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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.

Latest COLA and NAVGEM (NOGAPS) model is now differing on the track forecast from this time.
COLA model suggests that "Mahasen" will track N-W for another 12hrs and then re-curve N-N-E towards Bangladesh. And expects the system to make landfall over South Bangladesh coast on 16-May.
Why this N-E movement?? For answer refer to JTWC warning above.!

NAVGEM (NOGAPS) model suggest that the system will continue to move N-W during next 24hrs and then will try to re-curve N-N-E. Eventually the model expects the system to make landfall over N-E Andhra and South Odisha coast on 15-May.
This is a possibility like that of Cyclone "Laila" during same time of year in 2010. Similar kind of predictions where in place during that time as well. Some of the other environmental conditions may differ.

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.

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