The first big rainstorm of the season may be on target for Santiago and central Chile as a whole.
The storm will have potential to give 25 to 100 mm (about 1-4 inches) of rain over a wide area, even locally 150 to 200 mm (about 6-8 inches) along the Andes, between Monday and Thursday of next week. Rainfall this high could lead to flooding.
As of May 23, only about 20 mm of rain, little more than half the normal amount, has fallen since the first of 2013 at the city's Pudahuel Airport. City rainfall has been about 29 mm, well below the normal amount of 42 mm.
Normal May rainfall at Pudahuel is about 64 mm, a number that could easily be topped if the storm were to live up to its potential.
Deep low pressure forecast to stall off southern Patagonia together with a northward trailing will undergird the heavy rain threat. Added to this will be the windward slope effect as the storm's persistent water-laden winds mount the spine of the Andes.
The climate of central Chile is comparable to a Mediterranean or California climate, one in which nearly all of the rain falls during the coolest four to eight months of the year.
Numerical forecast model cumulative precipitation forecast valid 0600 UTC Thursday, May 30, 2013. For the Santiago area, located near the center of the image, precipitation onset would be early on Monday, May 27. Highest forecast rainfall (shown in magenta) for this scenario is 6-8 inches (about 150-200 mm) along the Andes south of Santiago.
The plum rains are known as "meiyu" in China, the "baiyu" or "tsuyu" in Japan, and the "jangma" in the Koreas. The heart of the plum rain season stretches from early June to mid-July, with a tendency to shift south to north across the affected area.
In the wake of the mid-June cloudbursts, most of Pakistan to northwestern India last week saw a return to dry, hot weather typical of the weeks leading up to the Monsoon onset. It was as if the Monsoon withdrew to its "normal" position for the latter half of June.
The 38.5 degree C (101 degrees F) reading Tuesday in Ajaccio, Corsica, may have been tops in Europe.
Monsoon Onset was June 13th, 2013, in Delhi, almost two weeks earlier than average. The June 15th onset at Karachi and Islamabad was more like three week ahead of schedule.
In Pakistan, hit-or-miss downpours missed the Sindh capital, Karachi. One did hit Pad Idan, where it left 60 mm of rain Wednesday. This was more than 20 times greater than the normal June rainfall.
It is still possible that this scenario is over wrought as to the intensity and spread of rain in Pakistan and northwestern India. However, it is the hunch of the present forecaster that some very unusual weather is going to unfold in the Subcontinent during the next week!