vagaries© of the weather.blog written by rajesh kapadia.concentrating on meteorology of the Indian sub continent and extreme world weather since 55 years For Any Information taken from here, due credit must be given to Vagaries.
Friday, April 29, 2011
Thursday, April 28, 2011
Monsoon Watch 4
Seasonal Low: Indicator: -ve
The days have started heating up in the Sub-continent since the last couple of days. 47c at Larkana in Pakistan 2 days back, and consistent 45s in the Rajasthan and Sindh regions (Pakistan) assure us of the seasonal low forming soon. But, what we still require are the severe heat waves, which are still missing.
The formation of the low is behind schedule, with the core region in the Thar desert still to form and lacks consistency. The MSLP in the Pakistan Sindh region is 1002 mb as of today. Lower since MW 3. But we must remember, that a series of W.D.s have been constantly keeping the temperatures down by as much as 5-7c below the normal.
As on end April, a pressure of 1000 mb in the central core region around Barmer is normal.
Bay Sector: Indicator: -ve
At least the high pressure mentioned in MW 3 is now dissolving, with the help of Southerly winds. Many international forecasting models indicate the formation of a low in the Bay by the 1st. of May. Pre- Monsoon low formation seen in the next week's time frame.
Previous MWs have stressed upon the importance of a low in the Bay by end April. Once a pre-monsoon low is formed, it increases the speed of the SW winds in the Bay sector. An ideal wind speed of 25-30 knts hastens the cloud formations.
Cross Equatorial winds: Indicator: -ve
Good and +ve development here since MW 3. In the western sector, the Arabian Sea branch, the winds below the equator are much better organised now, and have started curving near the equator. A Northerly gush is seen off the Somali coast. This ultimately leads to the formation of the "Somali Current" an essential formation required to accelarate the cumulus cloud formation in central Arabian sea.
Somali Currents are very strong S-N winds off the Somali coast, and this strong wind brings the SST off the coast down (by end May) to almost 18c ! With a warmer central Arabian Sea, cloud masses in huge volumes are formed in the Central area. (Shall discuss in detail in later MWs).
For now, it is sufficient to understand that the winds have turned Northwards, and have re-curved.
In the Bay sector, SW winds are organised South-West off Sri Lanka, and the SE winds from below the equator are pushing North in the Bay region. Signs of getting orgainised. SW winds just South of Sri Lanka have gained speed and are now clocking 25 ktns.
But, in the Arabian Sea and remaining sectors, the winds are still to gain speed. They could be considered weak.
With no cyclone in the Southern Hemisphere, the ITCZ could be forecasted to move Northwards. Currently it is around 5S. ITCZ movement discussed in MW 3.
200 hpa Jet Streams:Indicator:Neutral
Another parameter to observe now are the 200 hpa jet stream. Normally, they should be Easterlies right upto 20N by May end. This would facilitate the Northward movement of the Monsoon Current. Today, the jet stream is developing just below the Equator. Forecasts on models show these winds getting organised around the first week of May. Should march up to the 10N by middle of May, to be in time for the Andaman Sea Monsoon arrival.
La-Nina: Indicator: +ve
Sea surface temperatures in the equatorial Pacific Ocean have shown very little change. The weekly SST anomaly map for the week ending 24 April shows weak cool anomalies along the equator. Still, a few areas of SST anomalies of more than 1 °C cooler than normal for this time of the year now remain.
However, atmospheric indicators continue to be at odds, and remain consistent with a well developed La Niña event. The latest 30-day SOI value is +30.2. This is alomost touching the the highest April monthly value on record +31.7, recorded in 1904, and has remained consistently high throughout the event.
Cloudiness near the date-line remains below normal while trade winds continue to be stronger than normal.
Untill these indicators turn towards normal conditions, a fully neutral ENSO condition cannot be established. La-Nina prevails till then. And seems it could well slip into June.
Conclusion: Though there is some improvement in most of the parameters, there is still much to be achieved, and most parameters are still lagging behind time, and are -ve.
Based on these calculations, Vagaries would still maintain the Monsoon to reach Kerala by the 4/5th June. SWM should hit
First half of June should see some deficient rains in the
MW 5 will be up on 7th May.
Wednesday, April 27, 2011
Today’s Weather Across America: By Mark Vogan see blog for detailed U.S. Weather threat.
Another day of 'Extreme Weather' across the
GREATEST THREAT AREA
Monday, April 25, 2011
Saturday, April 23, 2011
Monsoon Watch – 3
Continuing from MW-2, "Bay of Bengal" low pressure parameter is a worrying factor. Normally, the Bay should host a pre-Monsoon low anytime after 15th. April. Like I mentioned in the previous MW, last year we had a cyclone in the Bay by the third week, and in 2009 a cyclone crossed the Bay on 12th April.
As on today, this region still maintains a luke warm response to the formation of a quick low. The pressure is anything but low, and the winds indicate a weak "high" trying to establish itself. What is needed now are winds getting Easterly, to start with, and break up the existing high pressure area.
Only +ve sign of a quick formation is that the SST is conducive. Map shows around 32c near the Andaman Islands. Ideal temperature for quick low formation.
However, The region below the equator in the Bay sector continues to be favourable with SE winds tending to bend SW South of the Bay in the 95E region.
Remember, the normal date for SWM to hit the South Andaman Sea is 15th. May.
Sub-Continent Seasonal Low: Indicator: - -ve
The line of dis-continuity should shift back to its normal position, in the centre of the Southern Peninsula region.
Out breaks of pre- monsoon thundershowers are expected normally in the southern states and South Maharashtra. We are having these now. Though the showers in the South are heavier than normai, and excessive. But, a break in the pre-monsoon thundershowers is common, and will allow the days to get hotter.
An exception this year is the Vidharbha region.With exceptionally heavy rians, and more quantum wise, the temperatures are just about managing 40c, in fact just hovering around the high 30s. Normally Vidarbha is a hotbed ! 45-47c is a "kid's playground" for the region.
Nights last year were terrible at this time. See in this link, check dates April 13th and April 20th.
And contrast this with the lows today.
The sesonal low in the Thar region is also lagging behind, thanks to the absence of intense heat waves. The days, have started to rise now. Trends of rising temperatures are finally seen in Gujarat and adjoining regions of Sindh across the border. Just saw the 1st 45c on Saturday, 23rd.April. (See write up below the MW-3)
True, the entire sub-continent region has to suffer a heat wave, but the gains are much more. The pressure around the Thar desert region is now 1006mb (994mb required by June beginning). There is no central core formed as yet. And ,as per the required scheduled development, a proper gradient is behind schedule in the making.
Cross Equatorial Winds : Indicator: neutral.
The cross equatorial wind flow, has just about picked up in the Southern Hemisphere. Winds, have not yet achieved the required speeds, but just about started hitting the East African coast. Re-curving Northwards of the winds, on the Kenyan coast, is yet to occur.
That means, a high pressure region, the back-bone of our Summer Monsoon, is also slow to form down in the Southern Hemisphere, off the Madagascar Island, and in the mid South Indian ocean.
However, Cross winds in the Eastern Sector (Bay) are getting strong, and are re-curving.
Amidst this, no cyclones are likely to form off Australia this season. If no low pressure forms there till end of April, the ITCZ can start moving North. And with low pressure and ITCZ moving North, the High in the Southern Indian Ocean has a fair chance of getting stronger and anchoring well.
As the ITCZ tracks north, associated MJO waves can "ride" alongwith. Meaning, after the shift, more MJO waves in the Northern Hemosphere (read Bay regions).
The positive news from Australian Weather Bureau; " it is likely that the next MJO event to progress into the Maritime Continent region will have little influence on rainfall and tropical cyclone activity in the southern hemisphere, but more likely will begin to influence northern hemisphere weather patterns."
La-Nina: Indicator: Same as Last MW.
La-Nina is almost the same as reprted in MW 2. Not much significant warming is seen in the region.
The 30-day Southern Oscillation Index (SOI) to 16 April was +26.5.
SST in the La-Nina zone are coming to normal levels very slowly. It should neautralise within 2/3 months.
If, by any chance, there is a delay in the La-Nina coming to normalcy, it would mean more than normal rains in June, decreasing in July.
Conclusion: As of today, there seems to be a slight delay in the
(This Monsoon chase is my personal view, and my personal analysis and deciphering is done as per my assumptions).
MW-3 coming up late tonite by 11 pm.
@9a it's already at 17C at Heathrow Apt, a rise of 3C over the past hour.
Friday, April 22, 2011
From Our Partner Blog:
TODAY'S WEATHER ACROSS UK & EUROPE By Mark Vogan
UK On track for warmest April on record, temps top 80 degrees in central
The normal is 14C in
Wardha gets 43 mms, Brahmapuri 36 mms and 15 mms in Nagpur as per IMD.
minimum temperature today in Amraoti is 17.8c, and 19.6c in Nagpur! 5c below normal !
Akshay from Nagpur gives the latest on Friday morning: "11mm rainfall in Nagpur with strong overnight thunderstorms."
Thursday, April 21, 2011
Wednesday, April 20, 2011
via e mail.
Tuesday, April 19, 2011
Sunday, April 17, 2011
Saturday, April 16, 2011
Further Analysis of the parameters as discussed in MW-1.
1. Seasonal Low: For this parameter, the -ve factor from the previous MW discussion is maintained, as the average day/night temperatures in the Northern Sub-Continent areas remain in near normal/below normal range.
IMD map of day temperature of the 15th April anomaly explains this.
A comparison with last year shows the difference this year. In 2010, the first 45c was touched on 10th. April, and on the same day Nagpur was 44c, Delhi 42.8c. Soon on 15 th April 2010, Nawabshah (Pakistan) soared to 47c, Simla to 28.2c on 16th, Ganganagar, Akola and Hissar to to 46c.
This year we are yet to reach 45c anywhere in the Sub-Continent.
The quick formation of the Seasonal Low due to absence of heat wave in Central and Northern regions of the Sub-Continent, continues to be un-favourable. Into the 3rd. week of April now, and the heat is missing.
As on 16th. April, the lowest pressure, in the Thar Desert region is at 1006 mb. (Last year 1002 mb this time) and this "low" area is restricted to a small area. As mentioned, it normally should reach a low nadir of 994 mb in June, and with 1008mb in the South Arabian Sea, a perfect gradiant is created to attract the south -west winds.
2. The La Niña event continues to decline in the Pacific Ocean, with a further warming of the SST in the past 2 weeks. On an average, it is warmer by about 0.2c over the last 15 days. The warming is consistent with the life cycle of past Niña events.
SOI was last measured at +26, equivalent as yet to a strongish LA-Nina event.
3. Last week, the Cross Equatorial Monsoon winds, which originate from the Southern Indian Ocean as SE winds, and cross the equator to become south -west,were weak, and not developed .
Let me explain, that the winds before crossing the equator break into 2 branches. 1) gushing into the Arabian Sea, and 2) moving into the Bay of Bengal.
Today, we find, the winds south of the equator better organised in the Bay branch, in the region south of the Andaman Sea. SW Currents are seen off the Sunmatra coast. And that is exactly where the start should be.(See extreme right of chart).
The Arabian Sea branch is still struggling to get organised. Here, a fall in wind speed off the Kenyan coast has disrupted the SE flow.Not a healthy sign,but could always re-organise fast.
The Mascrene high pressure zones in the South Indian Ocean, at 1030 mb, between Madagascar and Australia, have been observed, and the "Power House" of the Monsoon winds is slightly behind schedule,for this time of the season.
4. Another factor, which helps the winds gain strength, and bring more moisture into the Indian landmass, is the sea temperatures on both sides of the Peninsula. Optimum (warm) temperatures will hasten and create more clouds, and help in faster forming of the lows from the Bay. This parameter, is not very "normal" and tilting towards "un-favourable" as on date.
Put up the SST of last year on date. Comparison shows it was much warmer last year, i.e. above normal.
But the pre Monsoon Low in the Bay is still elusive. As discussed, we should see a low sometime after the 15th. of April. But as on today, a high pressure region prevails over the Bay.
5. To bring the existing SE winds above the equator, the ITCZ should move northwards. Around 1st. of May, this should cross the equator. The ITCZ, is in its "normal" position, as of now, at 5S. An indication is the Australian Monsoon Trough, now stationary north of Australia, around 10S, with TC embedded.
Ceasing of TC activity is a must for the ITCZ to start shifting.
So, overall, we can summarise as:
Parameter:1): -ve. 2):
Most parameters are running -ve. as of today. In today's situation, Monsoon arrival in Kerala could be delayed by about 4/5 days , and on normal dates in the
But, situations can change fast, and by the time we discuss the next MW, some -ve factors can suddenly become +ve. So, MW discusses and follows the developments as they emerge, and discuss the parameters as is where is.
No model can commit from today when the Monsoon can arrive. Things get clearer by first week of May. Vagaries' (in MW) normally remains true to estimates around early May.
Next MW up on 23rd. April.
Friday, April 15, 2011
For some light Reading.. See Space News Page
An article all of us missed out in 1835…. The Great Moon Hoax of 1835
by NANCY ATKINSON
Thursday, April 14, 2011
Wednesday, April 13, 2011
Tuesday, April 12, 2011
Monday, April 11, 2011
50th Anniversary of Human Spaceflight !...those interested see Space News Page.
Sunday, April 10, 2011
Monsoon Watch - 1
These reports are my personal views, study and observations. Estimates and forecasts are also my own calculations and views, and may/may not tally with any other estimates. The Monsoon progress as analysed will be discussed and explained in Vagaries.
This annual series is a follow up and chasing of the South-West Monsoon. For now, this series will be chasing and closely following up the actual developments of the monsoon, and analyse its progress. We are not yet contemplating the quantum of rains or the monsoon strength as yet.
Very very briefly, let us first understand, that the "power house" of our SWM is actually based far away in the southern Hemisphere. The main "generating factory" is the Mascrene Highs, SE of the Madagascar coast. The proper formation of these high regions,(1028 mb at least) will boost and create proper SE winds to lash the East African Coast near the Equator, and then turn SW in the Northern Hemisphere.
And the formation of the "Tibetan High" is another factor. An anti-cyclone in the upper atmosphere over the Tibetan Plateau. During the formation stages, there will be thunderstorm activity in the SE parts of Tibet during the months of April and May.
To generate a powerfull SW wind, the cross equatorial flow must be strong and gusty. SW winds (ultimately upto 600 mb levels) then are capable of riding on the warmer Arabian Sea waters and bring cloud masses towards the West Coast of India. In the Bay, similar SW winds are generated, but from SE winds below the equator, just below Sri Lanka.
And to attract the SW winds, again, we need a good proper "seasonal low" to develop in the Sub-Continent. This seasonal low, normally should start forming around Barmer, Rajasthan, by mid April, and at its peak stretch upto Arabia. Seasonal low at its peak, in June, should normally be around 994 mb, and the ridge around Kerala should be 1008 mb. This enables a good gradiant to pull the SWM inland.
In this initial stage, we will observe the basic root and foundation,the initial parameters and the initial seed of the monsoon.
1. Cross Equtorial Winds from Southern Hemisphere.
2. Seasonal Low over India/Pakistan.
3. El-Nino Status.
4. Pre Monsoon Low in the Bay.
1. Cross Equatorial Winds should start forming, and taking shape from mid -April, especially in the South Indian ocean region.
The Mascrene Highs are the main "Power House" of the South -West Monsoons.This generates the South -East winds, which after gaining strength, cross the equator and become south west. For a proper High to form in the South Indian Ocean, the cyclone season (Low pressures) should completely die down from that region.
Weak signs of initial SE winds forming, but not yet getting organised. Initial forming has commenced off the East African Coast. But the winds are NE above equator. Also, very Strong wind currents are required to be observed near the Eastern side of the Indian Ocean, as the Monsoon stikes the Andaman Sea by mid May.
2. Now, we have just about "normal to below normal" heating in the plains and Southern regions of the Sub-Continent. This is not much of a plus point in the formation, or a quicker formation of one of the important pre- monsoon weather requirement, the seasonal low. The seasonal low, stretch over Arabia thru India, normally starts forming in the Barmer and adjoining regions in the second week of April. Today, the MSL is around 1010 mb in the Sindh/Rajasthan region.
In the "core seed"area, it 1008 mb. (The ultimate low in the core, in June when ready, should be 994mb.). Today, there is a "high" of 1008 mb covering almost the entire Indian region.
The Seasonal Low normally is required to start taking shape for the monsoon by the second week of April.
3. La - Nina factor is favouring SWM as of now. It seems to be weakening, and approaching near normal levels. Forecasted to go neutral by June. Last SOI reading observed was +23. This actually indicates an surviving La-Nina.
• The Oceanic Nino Index (ONI) is based on SST departures from average in the Niño 3.4 region, and is a principal measure for monitoring, assessing, and predicting ENSO. The readings for the last 2 quarters were:-1.4, -1.3 and -1.2. La Niña: characterized by a negative ONI less than or equal to -0.5 C, so today La-Nina prevails.
4. Another pre monsoon seasonal normal requirment is the creation of a low in the Bay by the second week of April. This is necessary to trigger off the flow and formation of lows from the bay.
Progress this year is bad, as the Bay shows a ridge today. High pressure is prevelent in the Bay. No forecast of any low as of now. (in 2009,a low formed by the 12th. of April, and later it intensified into cyclone "Bijli", 2010 had no low till 3rd week of April).
Summary: Parameter; 1. normal, Parameter 2. -ve, Parameter 3. -ve. Parameter 4. -ve.
New Readers, please note, Parameters are normally (every year) considered in MW Series to guage and estimate the arrival cate of SWM, not strength. Time of arrival normally indicated after mid-April.
Next update on 17th. April.
Saturday, April 09, 2011
25th March Evening Let's Appreciate when the Air Quality is Good
The low, has literally "whizzed" past,and thru the central regions, and by saturday night, is already over south Rajasthan/Gujarat...