Tuesday, September 06, 2016

Hurricane Newton Moves Northward Much Faster Than Forecast

See Mike Leuthold's detailed discussion re Hurricane Newton as of yesterday afternoon at -

Above is yesterday morning's NHC outlook for Hurricane Newton (then a Tropical Storm) - that forecast indicated Newton to be along the southern Baja coast by by around 6:00 pm MST this evening.

However, Newton has already struck southern Baja before sunrise this morning. Satellite image above from 1230 UTC indicates Newton's eye along the coast north-northwest of Cabo San Lucas. This morning's outlook from NHC is shown below. This forecast indicates that Newton will still be at tropical storm strength as it approaches the border near Nogales tomorrow evening.

However, both WRF model runs from Atmo at 06 UTC last night forecast the Newton circulation to continue moving northward faster than the NHC forecast. The two 700 mb WRF forecasts here are both valid at noon tomorrow. The NAM version (above) forecasts the center of Newton to already be in eastern Pima County, while the GFS version is slower and forecasts the center to be along the border west of Nogales at noon. The NHC outlook indicates that Newton would be a Hurricane at noon tomorrow, located over the GoC near Guaymas. This is a very large difference and the actual speed with which Newton moves northward will determine the timing and evolution of our weather in southeastern Arizona.

The GFS version of the 06 UTC forecasts keeps Newton at tropical storm strength as it cross Pima County. The forecast above is for 10-m winds (kts) valid at 3:00 pm MST tomorrow afternoon.

Finally, both versions of the model forecast the heavy swath of rainfall with Newton to impact the metro area. Both forecasts here are for total rain through 6:00 am on the 8th - NAM version above and GFS below.

The behavior of weakening hurricanes/tropical storms coming ashore at the north end of the GoC is notoriously fickle and difficult to predict in detail (see my posts concerning Hurricane Odile that begin on September 15th, 2014). However, this situation is potentially one that could seriously impact the metro area, and a careful met watch of Newton's real-world behavior and speed of movement is essential during the next 18-hours.

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