Asia’s Monsoon 2015 has progressed, so far, unexpectedly. The Indian monsoon is advancing Faster than average and has delivered slightly more than normal rain. This is of vast economic importance to India, which is dependent on predictable rainfalls in order to meet GDP expectations and feed her own people. There are of course issues regarding mountain climbing as well.
The Mechanisms that cause and influence monsoons aren’t yet fully understood. The Indian monsoon may be related to a phenomenon high up, far away, over the Himalayas. The heating of Tibet’s plateaus creates an upper-level Low in the months when the sun’s rays are most intense, which drags the sub tropical jet stream often located high above the western Indian Ocean toward the mountain peaks. The result is winds blow from the southwest bringing moist air on shore. As the air is forced to rise over the foothills of the Himalayas, it causes constant and frequently heavy rains.
El Nino normally Dries southern Asia by pushing potential precipitation toward the central Pacific Ocean. The southern sides of the region’s islands are the only locales that typically receive above average precipitation during El Niño, due to a shift in general wind circulation and minor orographic lift. The South Asian Climate Outlook Forum (SASCOF), a division of the World Meteorological Society, has been tracking abnormally warm west and central equatorial Pacific temperatures since September. The eastern Pacific is now also experiencing warming, completing the requirements for weak El Nino conditions. There is a projected 70% chance that they will persist during the Southwest Monsoon season.
Based on this El Nino and other factors forecasts from April it was predicted Below Normal
rainfall totals but thus far have been entirely wrong, showcasing meteorology’s present shortcomings. Kathmandu, Nepal in June only saw 53% (141 mm of 263 mm) of its typical rains but, if we add the total from July 1st (104 mm), the ratio adjusts to 93% and shows how quickly things can change.
India’s leading private weather forecasting firm, Skymet’s April 22nd forecast, however, predicted monsoon rains of 2% higher than the 50-year historical mean. Their prediction hinges on the effect of the Indian Ocean Dipole, caused by the temperature differential between a particularly warm western and a relatively cold eastern Indian Ocean. The phenomenon reinforces the typical westerly flow over the Ocean onto subcontinental India and brings additional moisture, countering the confiscation of southern moisture caused by El Niño conditions.
The difficult part is what impact this will have on mountain climbing. There might be more questions than one can provide good answers to. As you can see from the above discussion there are many moving parts to this.
The one question is if this monsoon’s progress continues at the faster than normal rate does that mean a faster than normal retreat. So if we have a faster than normal retreat does that bring a longer period of dry conditions for the Karakoram Range?
Also if the monsoon retreats faster than normal does that provide an earlier start to the post monsoon climbing season for the Himalaya?
The final question is the impacts of El Nino and number and intensity of cyclones this fall. Although there can be less cyclones this fall when we have an El Nino that are many other factors that impact this. If you want to look at an Article this one is a little technical but has lots of interesting details.
Written by Meteorologist Geoff Linsley with summary comments by Meteorologist Michael Fagin.