CATEGORY 1 CYCLONE LEHAR WRAPPING IN DRY AIR?

METD WEATHER
Akshay Deoras
Severe Weather Forecaster,

Today afternoon, Tropical Storm LEHAR intensified to a Category 1 Cyclone as its max sustained winds reached 65 Kt and as of this post continue to be at 65Kt as the cyclone tracked west-northwest at around 07Kt (13km/hr) in the Bay of Bengal about 965km SE of Vizag,1100km east-south east of Machilipatnam,1050km east - south east of Kakinada,Andhra Pradesh and having tracked 200km from Port Blair after bringing heavy rains and winds in the Andaman and Nicobar Islands. However I am personally not convinced with the latest image of the system and some more observations, lets have a look here

Dry Air-

Like mentioned in yesterday's blog post, the amount of dry air entering the Bay of Bengal from East/North East India is increasing every hour as Cyclone LEHAR continues to act like a magnet doing this job. A 24hr comparison of the CIMSS Total Precipitable Water (TPW)clearly shows an increase in the spread of dry air which even now seems to be wrapping around the system in its northern periphery.

The topmost image shows TPW as of yesterday and the below image shows the latest precipitable water. One can see that blue,green region has moved further down (southward) as the Cyclone LEHAR presently at 12.5N,91.0E continues to move NW. Possibly the dry air is interacting with the outer rainbands- Northern and North-Western rainbands of LEHAR as can be possibly inferred from this latest IR-NHC imagery via CIMSS

The 1330UTC obtained NHC enhancement image shows a more or less oval structure of the CDO (Central Dense Overcast) feature which continues to obscure the LLCC. An animation of the IR imagery shows the centre is losing the convergence. It also indicated a possible exposed LLCC (although for a short time) and that the convection is possibly re-organising around a new centre marked by a very favoured wind field as can be seen in this image

The above IR BD image has contours of lower air convergence imposed on it. An increasingly favourable 30Kt region is developing coupled by an excellent poleward flow of 40Kt peak.
SST continues to be very favourable, in the 29C range which is overpowering the moderate 20kt wind shear in the region.

An analysis of all indicates that dry air has likely collided with the outer northern rainbands of Cyclone LEHAR and the convection is re-organising around a new centre and the system is overall maintaining its intensity. Over the next 12hrs, Cyclone LEHAR shall intensify gradually although I don't expect a Rapid Intensification yet considering the fact that wind shear are forecasted to remain moderate all the time in LEHAR's journey. Dry air wrapping shall be a factor to watch out and hence still I don't expect it to intensify beyond Category 2 which shall happen later tomorrow,26th Nov.

Given the fact that dry air interaction will act as a barrier and the SST will be decreasing beyond  36hrs from now ( morning of 27th Nov 2013), LEHAR shall make a landfall as a Category 2 cyclone close to Kakinada,Andhra Pradesh on the morning of Thursday,28th Nov 2013. The state of sea in the Bay of Bengal shall remain ROUGH in this period and hence fishermen shouldn't venture out in the sea till Friday,29th Nov 2013.


More details are awaited like potential damage to Andhra Pradesh coast which will enable to put the graphic map so STAY TUNED!!!

Tropical Storm "Lehar" threatens India!

METD WEATHER
Akshay Deoras
Severe Weather Forecaster

With just over a month from the landfall of disastrous Category 5 cyclone Phailin  and just a few days after Tropical Storm Helen , the Bay of Bengal is all set to host another Tropical Cyclone which will be soon officially called as "Cyclone Lehar".. At METD WEATHER, Saffir Simpson Scale is followed and hence we have already named the area of deeply organised convection about 1560km SE of Vizag,Andhra Pradesh as Tropical Storm Lehar given the estimated maximum sustained winds of 35kt as of today morning. This Tropical Storm which at present lies in the periphery of land, The Andaman and Nicobar Islands is all set to pass dangerously between Little Andaman Island and Port Blair between late tonight, 24th Nov and morning of tomorrow,25th Nov 2013 as a "Tropical Storm category" with max winds reaching upto 100Km/hr accompanied by strong rains and storm surge likely upto 10ft.... Lets have a look at the dynamics of Tropical Storm Lehar in the Bay of Bengal-

Shown above is a composite view of Tropical Storm Lehar. The topmost simple Infrared view (top left) and IR-BD view (Top Right) clearly shows almost circular convection centre with cloud tops reaching upto -70C which is an indicator of organising convection and intensification of the system. Interesting thing to note in the lower images is the organising of outer bands- rain bands- banding feature around the LLCC (Low level circular centre) as can be inferred in the NRL images. The lack of symmetry is being attributed to the periphery of the land which isn't allowing the system to undergo rapid intensification stage as it churns in the sea having temperature of 29C...

A look at the wind profiles & dynamics show that Tropical Storm Lehar is being troubled by moderate wind shear of 30kt to the north and south of the centre and 20kt to its East disabling it to intensify robustly. Over the past 12hrs, convergence at the lower atmospheric profile has decreased slightly along with the poleward outflow which now stands to be 40kt peak as against 60kt peak 12hrs ago...

As the system steers North West slowly ( at present with a velocity of 17km/hr), after the encounter with Andaman and Nicobar Islands, the system shall get a clearance from land to intensify.

Shown above is the Sea Surface Temperature view via CIMSS.. Here Red colour represents Sea Surface Temperature of 30C, Orange shows 29C, yellow shows 27-28C. Thus the sea coupled with the moisture content will be favourable for intensification. But the question arises, will Tropical Storm Lehar reach a Category 5 status like Tropical Cyclone Phailin ??

The answer at the moment seems- NO

Here is the reason,

This is CIMSS view of the wind shear in knots across Bay of Bengal.. Here solid white lines indicate an increasing shear tendency: unfavourable for storm intensification. Over the Bay of Bengal, it seems the wind shears will remain considerably higher than they were during Phailin's time as a result this factor will always try to reduce the intensity but with other factors favourable, Tropical Storm Lehar shall intensify to atleast Category 2 although JTWC says it can go upto Category 3. As the sea few hundred kilometers offshore Odisha and Andhra Pradesh is slightly cooler, intensification may not be that high and hence for now, people shouldn't panic or compare this cyclone with Phailin or Supercyclone of 1999 or with the US hurricane like Katrina.

Where will it head ?

This is always a million dollar question. At the moment, the sub tropical ridge seems to be steering the system towards Indian coast but the area in North Bay of Bengal is being monitored for the development of high pressure at the lower levels (850mb or say 5000 ft AGL). If the high pressure forms in that region, the cyclone shall not move much North in its NW journey and in that case its region of landfall shall be south of Vizag in Andhra Pradesh on the morning of 28th Nov 2013, Thursday.. 

However as GFS 00z is showing, if the high pressure doesn't form, system under the influence of sub-tropical jet stream of India will curve a bit north and make a landfall near Brahmapur,Odisha- apparently at the same place like Cyclone Phailin on the morning of 28th Nov 2013, Thursday

Where ever it shall head, people living along the coastal line from Kakinada,AP till Brahmapur,Odisha shall pay attention towards the development of this system which will be covered on METD WEATHER's facebook page (www.facebook.com/deorasakshay) and on this blog also

Once the forecast becomes more clear, an alert map will be issued by METD WEATHER

*** Preparation*** 

Rough Sea of Bay of Bengal will start now onwards and will continue till Thursday,28th Nov. Fisherman are requested not to venture with their ships/boats.. 

VIA BOM,Australia (People of Andhra Pradesh-Odisha Coast must note) 

When a cyclone watch is issued

• Re-check your property for any loose material and tie down (or fill with water) all large, relatively light items such as boats and rubbish bins.
• Fill vehicles' fuel tanks. Check your emergency kit and fill water containers.
• Ensure household members know which is the strongest part of the house and what to do in the event of a cyclone warning or an evacuation.
• Tune to your local radio/TV for further information and warnings.
• Check that neighbours are aware of the situation and are preparing.

Arabian Sea system shows "signs" of life after models kill it! BOB Depression/TS to impact Tamil Nadu

METD WEATHER
Akshay Deoras
Severe Weather Forecaster

Bay of Bengal Update- 

As was expected, the BOB system ( hence to be called as Tropical Depression) is churning in the Southern Bay of Bengal.

The above morning IR-BD imagery shows the exposed LLCC centred somewhere in the 9.5N,83.5E which is ~ 530km SE of Chennai.
So far the max sustained winds are around 55km/hr with MSLP ~ 1002mb.

The system has intensified since the last post due to favoured conditions. The model analysis suggests that the system is moving in a region of 30kt upper air divergence and around 15kt low level convergence with the V wind shear to be around 10kt.

Based on the models and observations, it appears that the system which at present is a Tropical Depression will INTENSIFY to a marginal Tropical Storm status ( With max sustained winds of around 65kt )

As a Tropical Storm, it shall head for a landfall in a region

 Between Ammapatam to Cuddalore ( Tamil Nadu) 

    ON Tuesday,Oct 30 2012 night period to Oct 31 2012 Wednesday early   morning hours- 

(10PM IST- 0400hrs IST) 

IMPACTS- 

* ROUGH SEA WILL CONTINUE NEAR THE TAMIL NADU COAST TILL 1ST NOV 2012 

* STRONG GUSTY WINDS WILL BE WITNESSED in ENTIRE TAMIL NADU, PONDICHERRY ( PUDUCHERRY),COASTAL BORDERING ANDHRA PRADESH BEGINNING TONIGHT AND ENDING AFTER THE SYSTEM PASSES

* HEAVY RAINS  ARE LIKELY IN THE AREAS IN CYCLONE's PATH AND ADJOINING AREAS AS SHOWN IN THE MAP AND THEN STRETCHING AS NORTH AS HYDERABAD on 31st Oct 2012 AS THE SYSTEM MOVES. MODERATE RAINS IN KARNATAKA AS WELL. 

* CHENNAI ALSO WILL WITNESS HEAVY RAINS,WINDS IN THE PERIOD 

* Flooding Potential across INTERIOR TAMIL NADU 

After the landfall, the depression will move inland and will be steered by the upper air winds which will move the system North-North East wards on Oct 31 due to which the rainfall shall spread into Karnataka,Andhra Pradesh,Maharashtra and the entire Eastern coastal states on 1-2nd Nov 2012. 

The rainfall then shall spread further reaching Northern Maharashtra-Central MP latitude by Nov 2-3 2012 due to which Nagpur will get rainfall in a period between 1-4th Nov 2012 with cloud skies. ( For exact details refer METD WEATHER FACEBOOK PAGE) with highest chances of rains on Nov 2-3. 

II- Arabian System- 

The recent GFS models have turned a lot since the last post and now they aren't showing any chance of Arabian System to form or it merging with the Bay Storm/Depression. 

Infact as was reported on METD WEATHER Facebook, the system faced a lot of problems on Oct 28th i.e yesterday as there was no proper low level convergence to grip the convection. 

However things changed today and lets have a look-

Animation- 

http://rammb.cira.colostate.edu/products/tc_realtime/loop.asp?product=4kmirimg&storm_identifier=IO962012&starting_image=2012IO96_4KMIRIMG_201210282200.GIF

Above- 

The top most image is of 28th Oct 0730GMT where the system faced a lot of problems due to lack of LL convergence. The below image is of Oct 29 0730GMT showing that the system has organised a lot since last 24hr given the developing Low level convergence of around 10kt. 

The system continues to remain in an excellent poleward outflow ( associated with the Bay system) of around 30kt and favoured SST to support robust convection. The wind shears are also relaxed (vertical). 

Here is a look at the latest precipitation embedded in the system- 

One can observe that outer rain bands have formed and there seems to be a developing LLCC with more banding from the Southern periphery of the system

Thus, I do expect that the Arabian Sea system will intensify further given the excellent conditions available. However, there is a decreasing confidence at the moment whether the system will head towards Gujarat or not. 

Considering the model runs and vicinity of the Bay system, it appears that the Arabian Sea system shall head NE gradually and move inland somewhere in Karnataka when the Bay system will be present. So in such a case, the chance of Arabian System forming into a Tropical Cyclone is very very less. However it can get converted into a Tropical Depression, move NE and move inwards in the Western Coast of India

As a result, the warnings issued previously for Gujarat STAND CANCELLED

TROPICAL CYCLONE/DEPRESSION ALERTS FOR INDIA

METD WEATHER
Akshay Deoras
Severe Weather Forecaster

"THE TROPICAL CYCLONE/DEPRESSION ACTIVITY BOTH IN THE ARBIAN SEA AND BAY OF BENGAL IS EXPECTED. STORM TRACKS CAN THREATEN INDIA"

"" FOR THE LATEST UPDATES, FOLLOW METD WEATHER ON FACEBOOK"""

The flattened 2012 North Indian Ocean Cyclone Season has revived with two candidates. BOB 01 and Tropical Storm Murjan. As METD WEATHER doesn't consider it, lets not discuss those past systems.

I- Bay of Bengal ( BOB)

The above DUNDEE imagery ( IR) spectrum shows massive CB clouds in the Central BOB with cloud tops around -30C at the moment. The imagery is of 0530PM IST. 

Animation (IR) here shows how the system has evolved robustly. 

http://rammb.cira.colostate.edu/products/tc_realtime/loop.asp?product=4kmirimg&storm_identifier=WP932012&starting_image=2012WP93_4KMIRIMG_201210270900.GIF

The above imagery shows that the system has organised much as seen from its symmetrical geometry. The system is encountering a building ~10kt convergence at the lower levels with extremely favorable thermodynamic conditions. The system continues to have 20kt upper air divergence with relaxed wind shears (vertical of 05-10kt barely) to support cyclogenesis in the 28-30C SST in the region.

Considering the favoured conditions, it appears that the system is very likely to strengthen further in the next 48hrs before it approaches the Indian SE and Sri-Lanka coast. 

The system can advance further and get a "Tropical Storm" status in the next 48hrs...

Where will it head? 

As per the 12z model which has been consistent, the system will be heading West and will make a landfall in a region between Cuddalore,Tamil Nadu and Northern Sri Lanka region. The area is purposively being kept large to settle the landfall uncertainties.  

The landfall seems to be happening on Oct 30 2012 in the morning - afternoon time ***
*** time may change***

Potential Impacts-

* Rough Seas offshore Tamil Nadu will initiate within 48hrs and will increase as the system approaches. 

* Heavy Rains with strong winds shall initiate in the Eastern Tamil Nadu region from 29th Oct and increasing ( VERY HEAVY) during the landfall. 

-------------------------------

II- ARABIAN SEA

The above DUNDEE imagery showing a wedge region of convection in the Southern Arabian Sea. So far the region hasn't shown any significant convergence and hence the system continues to remain widespread in the Arabian Sea. 

However, as the Bay System ( Possibly will be named Tropical Storm Nilam) will interact with the Arabian System and due to this, the moisture amounts of the Arabian System will increase. 

As the Arabian System moves as per the estimated NW track due to the upper air wind pattern, it seems that system will intensify robustly ( Its having around 15kt lower convergence, 10kt upper air divergence, around 5-10kt vertical wind shear, favoured SST), 

This system has a very high chance of getting converted to a Tropical Storm and due to its path, Western India will face some rainfall events. 

At present, at the upper level a shortwave trough is digging through India and as the trough exits which eventually co-incides with the system's northerly approach, the system will be steered by the jet streams which will start the system turning NE towards India-Sindh region

Model uncertainty exists at the moment however considering the consistency and the upper air pattern, it appears that the system will make a landfall somewhere near NW Gujarat-Sindh border 

on Saturday,Nov 3 2012 *** 

*** timings will vary*** 

The region of landfall is purposively kept wide to avoid uncertainties of the models 

The probable landfall areas ( will be modified suitably)

Entire West Coastal Gujarat,Sindh coast. 

IMPACTS-

Rainfall shall happen across Western Coast of India ( excluding Kerala) with more amounts towards Goa,Western Maharashtra,NW Maharashtra, Central Maharashtra and vicinity. 

LAKSHADWEEP ALSO WILL GET  RAINS AS THE SYSTEM WILL APPROACH VERY CLOSE TO IT

Mumbai,Pune etc will get rains around 3-4th Nov period *** 

The landfall impacts shall vary with the storm's intensity hence it shall be notified later on. 

Rough seas shall persists near the Indian coasts

STAY TUNED FOR UPDATES

Tropical Cyclone/Depression Watch CANCELLED for East,South-East Coast of India

METD WEATHER
Akshay Deoras
Severe Weather Forecaster



*** TROPICAL CYCLONE/DEPRESSION WATCH CANCELLED***
*** AS OF 06Z,21ST APRIL 2012 CONDITIONS NO LONGER EXSIST FOR THE FORMATION OF A SIGNIFICANT TROPICAL CYCLONE