Weather and micro-climate blogs (Copyright WeatherCast)

MUMBAI MONSOON 2019 PREDICTIONS: Blog post date: May 28, 2019 Mumbai monsoon is not just a season, it's a celebration. The people of Mumbai eagerly await the first showers, which signals the monsoon onset for the city and brings along nice and pleasant weather, abating the summer heat. The blowing breeze and sound of the dripping water make a delightful experience. The countdown begins... **So, what's in store for the maximum city during Monsoon 2019? Here is my take..** The onset is slightly delayed, owing to a stall in the monsoon currents. But the monsoon should start progressing again starting today/tomorrow. I expect the onset to happen between June 12-15 . This slightly delay in the onset has no bearing on the performance of monsoon during June 2019.  The 15 days are more than enough for Mumbai to reach the climatological June average of ~ 523 mm rainfall. Further, the +IOD conditions would most likely give a push to the monsoon in the later half of Jun...

************************************** 2019 Monsoon Revised Predictions (Unofficial):       Blog date: May 14, 2019  ************************************** Near timely onset of monsoon   (since ENSO generally does not impact the onset). Hits Kerala on ~ June 2nd.  Mumbai ~ June 12th. 1. Mumbai, Goa, & Kokan - NORMAL 2. Kerala and Peninsular India - NORMAL 3. Central India - NORMAL 4. Coastal Karnataka:  NORMAL 5. East Coast- NORMAL 6. North-East - BELOW NORMAL 7. Gujarat and Northwest - BELOW NORMAL 8. North India- BELOW NORMAL 9. South India (Interior TamilNadu, Interior Karnataka and Andhra) - BELOW NORMAL ****OVERALL SWM 2019 - NORMAL (~ 97% - 98% of LPA) **** **************************** Basis of revision: **************************** In my last post, I had indicated that three factors hold the key, namely, ENSO, IOD, and MJO. In the past month conditions have changed a bit, hence this revision. M...

T he buzz is back as the monsoon 2019 season nears. Already a bunch of predictions are pouring over the internet, so here's one more to add to the reader's confusion! :).  *********************** MY PREDICTIONS   (Unofficial): *********************** TIMELY ONSET OF MONSOON (since ENSO generally doesn't impact the onset) -  Hits Kerala on June 1st (+ 2 days).  Mumbai ~ June 11th (+2 days). 1. MUMBAI, GOA, & KOKAN COAST -  NORMAL/SLIGHT EXCESS 2. KERALA  & PENINSULAR INDIA -  SLIGHTLY BELOW NORMAL 3. CENTRAL INDIA, MARATHWADA, VIDARBHA -  BELOW NORMAL 4. EAST COAST -   SLIGHTLY BELOW NORMAL 5. NORTH-EAST -  NORMAL 6. GUJARAT, KUTCH, NORTH WEST -  BELOW NORMAL 7. NORTH INDIA -  NORMAL 8. SOUTH INDIA (INTERIOR TN, INTERIOR KARNATAKA, & AP) -  BELOW NORMAL **** OVERALL SWM 2019 -  BELOW NORMAL (92-95% of LPA) **** OVERARCHING CONCLUSIONS: 1. Interior Karnataka, Andhra, Mar...

Most anticipated North East Monsoon (2018) finally made onset of November 1st, after playing hide and seek for the entire month of October. Despite the late onset, some could argue that October for south India was pretty good (especially Kerala and TamilNadu), with some places getting above normal rainfall (especially Nilgiris and Delta regions). Following the onset, the southernmost districts of TamilNadu got lashed, recording first 200 mm daily R/F accumulation. Chennai and rest of TN got moderate rains after the official onset.  After onset, a mini-break was observed, with the UAC system that formed around October 31st getting dissipated. However, another low pressure system (near SriLanka) will keep the NEM active during the Diwali season, with good rains primarily in South TamilNadu and Kerala. Places in North TamilNadu & Chennai, and south Interior Karnataka (e.g. Bangalore, which has not been getting good spells) will have to wait for a...

C yclones are massive vortical (i.e. spinning) systems with immense kinetic and thermal energies, which form in the tropical oceans and move inland. They generally have a low pressure central core  surrounded by a high pressure anticyclone that helps in its intensification. Based on the core pressure & sustained peripheral winds, cyclones are categorised on a scale of 1-5. ( see: https://en.wikipedia.org/wiki/Tropical_cyclone_scales ) For any tropical cyclone, six key fluid dynamical parameters govern their genesis & track. (a) Sea surface temperature (>27 deg C for assisting cyclone genesis) (b) Effect of Coriolis force (f - parameter) (c) Low pressure centre (typically < 990 millibars) (d) Wind shear (<10 s  -1 ) (e) Presence of adjacent high pressure envelopes (which hinders with its movement) or any other phenomenon like a Western Disturbance and ITCZ movement. (f) Upper level steering winds. CYCLOGENESIS/INTENSIFICATI...

E lNino Southern Oscillation, abbreviated as ENSO, is an interesting and a well-established interseasonal phenomenon that has an immense effect on the tropical monsoons. Very briefly, it is associated with the weakening or full reversal of the atmospheric Walker circulation cell, which forms in the Pacific Ocean. The Walker cell's preferential direction is east-west (easterly), created by the motion of trade winds, supplying moisture to Australia & Indonesia. However, during an ElNino cycle, it either weakens (thereby slowing down the trade winds) or fully reverses, where the trade winds now blow west-east (westerlies).  The Walker cell formation and its modification is driven by the ocean dynamics. During non-ElNino or neutral years, a cold pool exists in east Pacific - near South American coast due to upwelling (specifically Chile coast), and a warm pool is formed in the west Pacific - near Australia. This set up is quashed by a Kelvin wave , which one can  ...

W ith almost 75% of the Southwest Monsoon (SWM) season gone by, we enter the last leg of SWM 2018. A lot to cherish about SWM 2018 but at the same time, the erratic pattern of SWM 2018 won't be forgotten (#Kerala floods, #Kodagu floods, #Bihar drought etc.). The SWM 2018 made an early and powerful onset, but lost steam around end of July and August, bringing widespread fear about below normal monsoon. Current we are staring at a deficit of ~8%.  Had it not been for the very heavy rains in Kerala, the deficit would have been in double digits.  August is going to end on a larger deficit, compared to June and July. Inspite of three back to back low pressure systems in the #BayofBengal, August underlined the “Vagaries of Monsoon” -  be it in terms of below average countrywide rains or circulation system positioning itself at one place for a week and delivering non-stop rains). Overall, SWM 2018 couldn't keep up the pace with which it started. This is not surprising ...