(written Oct. 12) Tropical cyclone Hudhud is heading into a storm: a vigorous midlatitude upper-level trough approaching from the west.

In Figure 1, Hudhud is over India while the trough is a kink in the black 200 hPa height contours and the associated ball of cyclonic vorticity (red). They are forecast to “collide” Oct 14th over the Himalayan foothills.

Cumulative rain in the 0.5-degree GFS forecast (Fig. 2) reaches almost 200mm in western Nepal — comparable to amounts seen in the developing winter monsoon in Malaysia, Sumatra, and (to a lesser extent) Vietnam. The initially sharp trough seems to be blunted with time. But locally, valley by valley, there could be more. And the model could be wrong of course.

(Meanwhile, Japan will be under formidable typhoon Vongfong, also interacting with a broader trough in the westerly jet stream)

Animations of Fig. 1 can be seen at http://weather.rsmas.miami.edu/repository/alias/MiamiMonsoonLoops

Fig. 1. The GFS-analyzed situation (plus IR satellite cloudiness) at 18 UTC on Oct. 13 as tropical cyclone Hudhud approaches a strong midlatitude trough over northern India. 

Figure 2: Cumulative rainfall (mm) during Hudhud’s demise, in the GFS 0.5 degree forecast. Vectors at 850 hPa and height contours at 250 hPa are also shown.

(more…)