Friday, June 24, 2011

Many Interesting Things To Note - Part 2

The 500 mb analysis in previous post shows that the anticyclone over the Southwest still has a distinct connection to the Pacific subtropical high. However, this morning's 1200 UTC NAM forecast quickly makes the eastern portion of the 500 mb high dominant, so that by 36-hours (above) it has clearly become an over-the-continent lobe of the Atlantic subtropical high. This lets the flow around the bottom of the anticyclone have a fetch across Texas, northern Mexico and then north into Arizona. While the 700 mb level is forecast to remain quite dry, there appears to be enough diurnal convection in Mexico occurring each day, that the southerly flow forecast around the anticyclone may bring residual moisture from decayed convective towers northward within a shallow layer centered around 500 mb. Thus, some high-based convection is possible over the mountains of southeast Arizona during the next several days. The early morning run of Atmo's high-resolution version of the WRF model actually forecasts some convective radar echoes on the Arizona side of the border tomorrow (Saturday the 25th) at 5 pm - see below.

In the longer term, there is a pronounced tropical wave (in the past referred to as an easterly wave) over the Caribbean - see GFS mornng analysis below. By 132-hours (Wednesday afternoon the 29th) this features has pushed westward across southern Mexico and Central America and is in the far eastern Pacific (see bottom figure) - thus, having some potential to be a player of interest to us during the last half of next week.
So, even though the blistering heat continues over southern Arizona, there are some things to keep an eye on this weekend!

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