Thursday, May 29, 2008
The "real" monsoon cloud mass, though not very strong and intent, has now formed today, as seen in the satellite image of 00UTC Thursday. The mass of cloud is near the mid Arabian Sea, away from the cold waters formed by the Somali current, and now gradually nearing the Kerala coast in a south-westerly direction.My personal observations are that the monsoon has hit the Lanka coast today,29th., with moderately strong winds and rain.
I see the monsoon hitting Kerala in 2 days, and then sliding north upto Karnataka coast in the next 2 days.The situation, in the northern region of the subcontinent, discussed in MW18, is gradually improving.The weak ridge in the Arabain Sea is still seen "faintly'', and the easterly jet streams at 200hpa are still yet to move north, being restricted by the westerly jets which are strong at 22N. Concurrently, the further movement of the monsoon can be restricted by a few days.
Monsoon should approach Mumbai by the 9th. Its strenght along the west coast may remain feeble upto the middle of June.The monsoon should advance into South Gujarat around 15th., and progress towards Saurashtra region in the next 3/4 days.
In fact, with the seasonal low formation being delayed this year, June rains may be deficient in Gujarat, north-west region and Maharahtra.(maybe upto mid July,as discussed in MW17).
Now, the ECMWF has, as of 0000 UTC Wednesday, given up on a major Arabian Sea cyclone. But, the 1200 UTC GFS forecast model has now shown an Arabian Sea cyclone that would end up landfalling upon Oman at the middle of next week.
I do not know whether there will be an Arabian Sea tropical cyclone next week. The situation, I feel, seem to be favorable for a monsoon low or tropical depression westward from southern India (heading towards Kerala as the monsoon current). Hence, we can observe the numerical forecast model scenarios and make our judgements on the uncertainties of the the weather !
Wednesday, May 28, 2008
Saturday, May 24, 2008
After the discussion in MW16, a W.D. in the northern region has played spoilsport again. On the 23rd. night, rains were reported from north Rajasthan and Pakistan and some areas of Punjab and Haryana. An upper trough is hanging on in the northern region for an unusually longer period.
Now, I estimate, that this has blocked the progress of the seasonal low and the said low is presently very weakly formed, at 1000mb, in the region of northern Sindh/adjoining Rajasthan.Temperatures in the north are still to reach the normal levels as on the 24th.
Consequently, the monsoon advance can be restricted. As per the estimate in MW16, the monsoon can advance upto coastal Karnataka by 1st. June, as a feeble current. Thereafter, I foresee a halt in the progress further northwards for another 8/10 days atleast, till the proper conditions are recreated.
For Gujarat, the monsoon may actually arrive only after 15th. June. It may require another 10 days( after the vanishing of W.D.s) of sufficient heating to form a proper gradient for the advance.
Also seeing the current situation, the fast vanishing La-nina, and the "slipping" SOI index, it may be difficult, in certain areas, for the monsoon rains to be normal this year. There may be some delay and below normal rains in June/early July. Hence the initial period of June/July will have to be watched and followed closely for regions in western and central India.
Friday, May 23, 2008
The Bay sst in the picture above is still seen as below normal. No forecast model indicates any major revival of rains in the bay, for the next 10-12 days.
Monday, May 19, 2008
Sub-continent Region: The entire northern region has now started heating up, to almost heat wave conditions.(That is temperatures of 6c above normal).
Thursday, May 15, 2008
Bay Region: Today, I was most surprised to get a message from Vinson( Business Line) to check on the JTWC site. They had mentioned the likely formation of a cyclone in the bay. I always felt that this is not a probability now. As discussed in my earlier blogs, that this low will eventually "rain off" in the north bay area within a few days. For it to remain weak, there are several reasons:-1. low convection around it. 2.back to back W.D.s,causing dry north-westerlies to push it away. 3. very much near/on the coast. 4. Bay sst not warm enough for the system to turn into anything beyond a depression at the most.
Check the bay sst anomaly above, they are still at least 1.5-2c below normal in most of the bay.
The streamline map above shows the winds weakening a bit in the central bay. The formation of a tropical storm in the south china sea in the next few days will pull the main south westerly flow of the south andaman sea towards it. Hence, I still feel, that the monsoon will advance in the bay , by the 20th. The further advance into the north-eastern states will commence only after the formation of a trough from Assam to the central bay region, say by the 25th.
Arabian Sea: Read todays forecast given by the IMD. The monsoon , according to them will advance into Kerala between the 25th.May and 2nd. June ! Leaves nothing to imagination !
If we compare the sst anomaly map above and the sst anomaly map of the same time last year( shown below), we see the Arabian Sea is much cooler this year, if the same normal temperature is taken into consideration. Last year the warming trend at this time was more, and this year the same region is cooler.
However, the somali winds as seen in the streamline map, are picking up, and a distinct cooling(yellow) off the somali coast is now seen. I feel, the sst of the Arabian Sea vis-a-vis the somali current and otherwise will be geared up for monsoon clouds to start forming in the sea off the Kerala coast from the 25th. Another 4/5 days thence, and the monsoon can touch Kerala.
Sub Continent: The jig-saw puzzle of the monsoon can fit in properly in the bay and Arabian sea, but I only hope the sub continent heating and seasonal low formation in the north do not play spoilsport. The heating even today(wednessday) is mediocre, with the highest in Pakistan today( 14th) at 47c, Nawabshah,and with only a stray 44c at Nagpur and Vijaywada in India. The heat low just about touched 998mb in a small area on the 14th. A difference of atleast 16mb in the pressure is required between the MSL at Trivandrum and the pressure in the heat low to create a gradiant to pull the monsoon winds and clouds inland.
Sunday, May 11, 2008
Thursday, May 08, 2008
Sunday, May 04, 2008
Bay Region: The water temperatures in the bay remains low after the cyclone. The image shows the temperatures around the centre of the bay as below normal (cyclone region), and the south bay also is seen as below normal. This has to heat up as discussed in the last blog, and create the conditions for the northward movement of the bay branch of the monsoon and a gush of the cross equatorial winds. It is still only 2 days since the passing of the cyclone, and the waters will heat up in a day or two, and maybe keep the date of monsoon over Andamans.
Sub-Continent Region: The region has started heating up exactly as anticipated.
Maximum temperatures on 4th.May
Nawabshah (Pakistan) 48°
Sibi (Pakistan) 46°
Jacobabad (Pakistan) 46°
Hissar Airport (India) 45°
Gwalior (India) 45°
Rohri (Pakistan) 45°
Kota Aerodrome (India) 44°
Amritsar Airport (India) 44°
Jharsuguda (India) 44°
Satna ( India) 44°
However, the weak W.D. passing through the northern regions today may not bring down the temperatures to a large extent, except provide a relief of a degree or two, that too for one day.
Arabian Sea: The water temperatures of the region still are seen as below normal in the above image. But it is some time before this needs to heat up. Even if the waters heat up in the next 10 days, the Arabian Sea branch of the monsoon will progress on the normal date.
Yet again,it seems the monsoon can be on time and as per normal date.
Shall discuss the intensity and performance of the monsoon as per available data next week.
Thursday, May 01, 2008
Bay Region: Severe cyclone "Nargis" is now moving away towards the Myanmar coast, and will hit the coast on the 2nd. Subsequently, the winds in the bay would take about 10 days to regroup back into pre monsoon formation as the bay water temperatures are now down to around 30c. Since, according to forecast models, the ridge aloft at 500hpa is moving away, the typical situation of strong south-westerlies from across the equator will be back into action near about the Andaman islands around the 11th./12th. The monsoon could advance into the Andaman Sea by the 14th.
Regions of south east Asia, and Thailand coast could get the monsoon rains from the 15th. Singapore and west Indonesia areas will get a spurt in rainfall activity due to the above reasons from next week.
Sub-Continent Mainland: The sub continent is now in for some severe heating in the next 10 days. From Kashmir to Maharashtra through Rajasthan, Delhi, M.P. and Gujarat, the days are forecasted to heat up . In Pakistan, the Sindh region will see temperatures go up to 48c in the first 10 days of May, and places in Rajasthan could see 47/48c and Akola or Nagpur may touch 47c. Gujarat may witness a 45c in a few places in the first week. This augments well for the formation of the seasonal low, which is forecasted to form around the 4th. by the NCMRWF. The weather is expected to be dry, except on the 3rd. when a weak W.D. crosses by and precipitates little rain in Kashmir.
Arabian Sea:With the developments, the ICTZ can cross the equator by the 10th. Subsequently. it will tone up the equtorial flow of south westerly winds in the Arabian Sea region, and the Somali current could strengthen after the 15th. The sea temperature needs to warm up still by 2c.
Hence Maldives and Comorin can expect the monsoon rains from 20th.
BB 18 A Low expected near the Andaman Islands by Monday 5th. System can strengthen to a depression or cyclone over the Bay of Bengal before...