Friday, October 03, 2014

What Will Become Of Simon?


This morning (Friday, October 3rd) TS Simon is is about due south of Cabo San Lucas (IR image above is from 1330 UTC) and moving west-northwestward. The morning forecast from NHC for Simon is shown below. Several things of note: 1) strong convection extends well northeastward from the TS, into the southern GoC at this time 2) NHC forecasts Simon to continue mostly westward until Sunday, when they forecast it to begin recurving under the influence of a trough in the westerlies approaching the Southwest 3) NHC forecasts Simon to become a hurricane during the day tomorrow, and 4) the track of Simon from NHC is fairly close to that forecast by the current run of the ECMWF - both the NHC and ECMWF seem to have been biased too far to the west for a number of this season's storms - so the actual track of Simon during the weekend will be important to watch.



At this time PW over the Southwest is VERY low, with values running around a quarter of an inch, or lower - above graphic is from CIRA at Colorado State and shows their blended PW analysis for 6 am MST this morning. The Southwest is very brown.

The current early run of the WRF-GFS model at Atmo forecasts a significant northward push of moist, mT air during the weekend. The forecast of PW below is valid at 11 pm next Sunday night. At that time the model forecasts high PW values to have reached the border in south-central Arizona. However, the model's forecast for the center of Simon at that time is north and east of the "official" NHC position forecast.

At this time, my guess is that the core of Simon will cross central Baja and move rapidly east-northeastward across northern Mexico headed toward the Plains. But, for southeastern Arizona the issue will be whether or not there will a strong enough intrusion of low-level moisture ahead and north of Simon to support showers and thunderstorms, ahead of the westerly trough mentioned above.


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