|Image: NOAA/National Hurricane Center|
|48-h loop of 925-mb winds, precipitable water, and IR satelite|
imagery ending 1500 UTC 29 July 2011.
We can track the remnants of Don in the GFS forecast initialized 0600 UTC 29 July. To do this, I've plotted 925-mb absolute vorticity and precipitable water. The former is a measure of the circulation accompanying the storm, the latter the moisture. I've also highlighted the 3.5 cm precipitable water contour.
During this period, precipitable water is generally high over the Gulf of Mexico and west of the Sierra Madre and along the Gulf of California. Lower precipitable water over the Sierra Madre at least partly reflects the fact that there is no lower troposphere over this high terrain area. As Don moves inland, it is accompanied by a surge of moisture into west Texas and northern Mexico. A careful look at the loop shows a slug of higher precipitable water (>3.5 cm) penetrating across the northern Sierra Madre, tracking pretty much over Tucson, and merging with the tongue of high precipitable water on the west side of the Sierra Madre. After that merger, the moisture associated with the remnants of Don is difficult to track.
|0600 UTC 29 Jul GFS forecast through 1800 UTC 1 Aug.|
925-mb absolute vorticity color filled, precipitable water
contoured with 3.5 cm contour highlighted.