Wednesday, November 02, 2011
Cyclone over Arabian Sea, successor brewing too
The deep depression over west-central Arabian Sea moved westward and intensified into a cyclonic storm named ‘Keila’ this morning.
Keila lay centred over west-central Arabian Sea west-northwest of Mangalore; 400 km north-northeast of Socotra Island (Yemen) and 150 km southeast of Salalah (Oman).
The system is likely to move westwards and cross south Oman and adjoining Yemen coast to the south of Salalah around tomorrow evening.
Meanwhile, as was forecast over the past couple of days, the upper air cyclonic circulation over southeast and adjoining east-central Arabian Sea has fathered a fresh low-pressure area.
An India Meteorological Department (IMD) outlook said that the system is expected to become ‘more marked’ over the next two days.
A follow-up tropical storm may be developing over the Arabian Sea basin, according to global model forecasts.
The rain-driving trough of low-pressure extending from southwest Bay of Bengal to west-central Bay of Bengal has also been put under watch for instigation of a tropical storm in the Bay of Bengal over the next few days.
After two-away going storms in the Arabian Sea, the building Bay of Bengal storm could turn out to be the first one to be of a direct threat to the Indian coast (Tamil Nadu coast), as per early forecasts.
But since these happen to be early forecasts, the developments in the Bay of Bengal would need to be watched for any signs of storm-building, according to independent experts.
Meanwhile, what seems to have transformed a hesitant depression into a named tropical cyclone overnight in the Arabian Sea is the favourable, though threshold-level sea surface temperatures, according to a US Navy’s Joint Typhoon Warning Centre (JTWC).
The environment was also aided by the presence of the seasonal anticyclone over west Asia and extending into northwest India, which occupied the space after the southwest monsoon exited the region.
The anticyclone provides the ‘window effect’ to the cyclone towards the top helping the system to ‘breathe’ and sustain itself.
But the JTWC saw the westerlies associated with a prevailing western disturbance over north Pakistan and Jammu and Kashmir guiding the system along the Yemen and Oman coasts to east-northeast direction.
The London-based Tropical Storm Risk Group saw the system making a landfall over the Yemen coast, which is similar in terms of the outlook held out by the IMD.
IMD models suggest HEAVY rain again for N. Tamilnadu coast and S. Andhra coast from tomorrow till 4-Nov.. http://ow.ly/i/kqAn
As Keila dies along Yemen coast on 4-Nov, the present S-E Arabian sea UAC will move W-N-W, a UAC will pop over S-E Bay. http://ow.ly/i/kqol
Today's circulation along Kerala coast will consolidate from tomorrow along the same location .. http://ow.ly/i/kqnG
Cyclone "Keila" ... makes landfall at 11:30pm near Salalah, Oman
Cyclone "Keila" ... makes landfall at 11:30pm near Salalah, Oman.
Now it has tracked North East
JTWC warning, 8:30pm IST
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Predicted track
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Latest satellite IR
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Now it has tracked North East
JTWC warning, 8:30pm IST
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TROPICAL CYCLONE (TC) 03A (KEILA) LOCATED APPROXIMATELY 630 NM EAST- NORTHEAST OF ADEN, YEMEN, HAS TRACKED NORTHEASTWARD AT 05 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE LOW LEVEL CIRCULATION CENTER (LLCC) OVER THE YEMEN COAST WITH A RECENT FLARE OF CENTRAL CONVECTION AND A RELATIVELY SMALL CONVECTIVE BAND TO THE SOUTH. THE INITIAL POSITION IS BASED ON THE MSI AND A 021233Z SSMI 85GHZ IMAGE WITH FAIR CONFIDENCE. THE INITIAL INTENSITY IS BASED ON A 020814Z OSCAT PARTIAL PASS SHOWING SUSTAINED 35 KNOT WINDS OVER THE SOUTHERN SEMICIRCLE OF THE LLCC. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS LOCATED IN AN AREA OF GOOD DIVERGENCE ALOFT, LOW VERTICAL WINDSHEAR (05-10 KNOTS), AND GOOD POLEWARD OUTFLOW, AS IT LIES CLOSE TO A POINT SOURCE OF DIFFLUENCE. KEILA IS CURRENTLY IN A WEAK STEERING ENVIRONMENT AS A MID-LATITUDE TROUGH TO THE NORTH HAS WEAKENED THE STEERING RIDGE. BY TAU 12 THE MID-LATITUDE TROUGH SHOULD HAVE EXITED THE REGION ALLOWING FOR ANOTHER MID-LEVEL SUBTROPICAL RIDGE TO BUILD IN FROM THE NORTH. SOUNDINGS FROM SALALAH, OMAN (17.03N 54.08E) SHOW NORTHEASTERLY FLOW FROM 700MB AND UP, THEREFORE INDICATING ANTICYCLONIC FLOW. THIS NEW STEERING INFLUENCE SHOULD TRACK TC 03A WEST-SOUTHWESTWARD ALONG THE COAST OF OMAN AND YEMEN. KEILA SHOULD BRIEFLY WEAKEN TO 30 KNOTS BY TAU 12 DUE TO LAND INTERACTION BUT THEN SLOWLY INTENSIFY TO 35 KNOTS BY TAU 36 DUE TO WARM SEA SURFACE TEMPERATURE (>28 DEGREES CELSIUS) AND GOOD OUTFLOW ALOFT. BY TAU 48 TC 03A SHOULD INTERACT WITH THE OMAN COAST AND GRADUALLY BEGIN TO WEAKEN AND DISSIPATE BELOW WARNING CRITERIA (35 KNOTS) WHERE IT SHOULD THEN DISSIPATE OVER WATER BY TAU 72. AVAILABLE NUMERICAL MODEL GUIDANCE REMAINS LIMITED, HOWEVER, ALL MEMBERS ARE IN GENERAL AGREEMENT ON THE SOUTHWESTWARD RECURVATURE IN THE TRACK. THEREFORE, THIS FORECAST REMAINS SIMILAR TO THE PREVIOUS FORECAST. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 021200Z IS 7 FEET.
Predicted track
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Latest satellite IR
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Latest IMD GFS models also suggest a South West movement from now and die along Yemen coast in next 48 hrs
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