Tuesday, September 25, 2012

Miriam Update

Update Wednesday 26 September - The latest NHC forecast (added below the other forecasts at the bottom of this post) for now TS Miriam has continued to change quite substantially. The storm has weakened and moved west of earlier track forecasts. The forecast now indicates Miriam to drift slowly northward fairly far west of Baja - this is similar to the behavior of TS Kristy during the latter stages of her life. So, the dangers inherent in 5 day or longer forecasting are well illustrated here.

Current Atmo early WRF-GFS forecast brings higher PW northward but keeps it along the Borderlands and into southwest Arizona. The model develops marginal CAPE in the same areas next two days. So it goes.

Update - edited to add the NHC 8 am forecast (down at bottom). The latest forecast has kept Hurricane Miriam on the same track, but slowed down her speed. The result is that the forecast for Sunday morning indicates Miriam still offshore south of the Baja spur.

Yesterday afternoon there were isolated, very light showers around southeastern Arizona, much as forecast by the models. The high temperature at TUS reached only 97F, after 4 days of 100F or just over.

The Hurricane Miriam situation remains as the main focus for the rest of the week. The storm was briefly at Cat. 3 intensity yesterday and is currently (see IR image above from 1130 UTC this morning) a Cat. 2 hurricane. The storm is moving a bit more slowly than was forecast yesterday, and remains south of Latitude 20N. The forecast from NHC this morning remains similar to that of yesterday. The storm is forecast to reach central Baja over the weekend. While low-level moisture will increase over southern Arizona, the precise impacts on our weather remain somewhat uncertain. There continues to be a very large spread in the global model forecasts, meaning that there is a considerable range of weather possibilities for southern Arizona (and California) as the storm moves northward. This continues to be a situation where we will just have to watch how things progress.

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