14 June 2015

Tropical disturbance entering Gulf, heavy rain headed for Texas

Back on June 4, I posted some model forecasts on Facebook that showed a disturbance coming together in the eastern Pacific on June 8, then crossing over the Isthmus of Tehuantepec/Yucatan area, then entering and developing in the western Gulf of Mexico on June 12-13, and finally, heading for Texas on June 14.  Well, as unbelievable as it sounds, that is playing out with near-perfect accuracy!  Such forecasts were made by both GFS and ECMWF global models.

Enhanced infrared satellite image from 7:30am EDT.  The approximate center of the disturbance is marked with a white X, with general forecast trajectories in white arrows. (NASA)
As of Sunday morning, the disturbance is over the Yucatan peninsula... there is a 1008mb surface Low embedded within it, but the cloud cover and thunderstorm activity extends over a much larger area.  It has a fairly high likelihood of organizing further once it's over the Gulf of Mexico, and an aircraft reconnaissance plane will investigate it later today to help decide if a tropical cyclone has indeed formed.

Since this is a relatively large and disorganized system, the exact center of it does not matter much, but it does gives an idea of where the envelope of disturbed weather will be.   No model, as of now, is forecasting anything beyond a mid-grade tropical storm (which only tells you about the wind speed... tropical storms can still be very dangerous, costly, and deadly because of the rain).

Track forecasts for 91L (pre-TD2 or pre-Bill?) from Sunday morning.  The first three models are global; the last three are regional, and all agree of a northwest track toward Texas, then recurving inland. (UAlbany)
 By far,the biggest threat from would could become TD2 or TS Bill is heavy rainfall and flooding in areas that will not take much to flood: Texas and Oklahoma.  This system could bring 6+" of rain to some of those areas, plus a plume of heavy rain along its longer-term trajectory (through the Ohio Valley and the northeast US).

Five-day forecast of accumulated rainfall totals, valid from Sunday morning through Friday morning. (NOAA/WPC)
Here is another view of a rainfall swath, from the 06Z run of the GFS model, and just over the south-central US...

Five-day forecast of accumulated rainfall from the 06Z GFS run, valid Sunday morning through Friday morning. (tropicaltidbits.com)
Stay tuned for further updates...