Monday, September 05, 2016

Tropical Storm Newton Heads Our Direction

Tropical Storm Newton is currently just west of Cabo Corrientes and heading northward. The IR image above is from 6:30 am MST this morning and the MIMIC PW analysis below is from 5:00 am.

This morning's NHC forecast for the track of Newton is shown above, with the intensity forecast indicating NHC expects Newton to remain a TS. However, the Mexican Weather Service has issued a hurricane warning for the southern end of Baja, as the storm is expected to approach rapidly across very warm waters. The NHC notes in its current discussion:

Low shear, a moist environment, and very warm water should allow
Newton to steadily strengthen until it reaches the Baja California
peninsula. In fact, rapid intensification is a possibility as the
SHIPS Rapid Intensification Index shows a 40 percent chance of a
30-kt increase in the winds during the next 24 hours.  Based on the
expected conducive environment, the NHC intensity forecast remains
near the high end of the guidance during the next day or two. After
Newton passes the Baja peninsula, weakening should occur due to land
interaction and an increase in vertical wind shear.

Shown above in the two graphics are GEFS plumes from the 06 UTC forecast last night of QPF (top) and PW (just above). The range of QPF from the different members' forecasts for TUS (the airport) is almost 3 inches and the range of PW is around an inch. This reflects the fickle nature of our actual observed weather when an old TS comes near.

The official NWS morning forecast for the airport grid box is shown below. The POPs stay at 50% or less for Wednesday and Wednesday night, but the forecast also calls for Heavy Rain during those periods.

Finally, I took a look at the 06 UTC WRF forecasts from Atmo. Both versions forecast Newton's remnant 500 mb circulation to cross central Pima County. The composite radar forecast above (from the WRF-GFS,valid at noon on the 7th) is quite impressive. The accumulated precipitation forecast from the GFS version (below valid through 11:00 am on the 8th) forecasts the core area of heavy rains directly into central Pima County and parts of the metro area. Amounts on the Catalinas reach 6 to 8 inches in the model forecast. The NAM version of the forecasts shifts the core of heaviest rainfall eastward across Cochise County. Regardless of how the actual details evolve, an interesting work week on tap.

1 comment:

  1. Good morning Bob: the approach of TS Newton brought back operational memories of Hurricane Nora in September 1997 while working the FCDMC Meteorological Services Pilot Program. While Nora's track was well west of the projected Newton track, it is worth noting that Harquahala Peak in extreme NW Maricopa County received 11.97inches of rain in 24hours setting the new Arizona 24-hr rainfall record. Here's a table with additional Nora rainfall's that exceeded the County's 24-hr 100-yr rainfall of 4.20inches/24 hours.
    Harquahala Mtn. 5185 5681 11.97 * Top of Harquahala Mtn., 36 mi. WSW of Wickenberg
    Yarnell Hill 5290 5128 6.65 1 mi. ENE of Yarnell, Yavapai County
    Wilhoit 5365 5043 5.39 At Wilhoit, 10 mi. SSW of Prescott, Yavapai County
    Mt. Union 5380 7495 4.57 Top of Mt. Union, 10 mi. SSE of Prescott
    Centennial Wash 5180 2417 4.53 1 mi. N of US 60, 19 mi. W of Wickenburg
    Horsethief Basin 5700 6702 4.37 At HB Recreation Area, 6 mi. SE of Crown King
    Tiger Wash Fan 5140 1605 4.17 1 mi. W of Eagle Eye Rd. and 4 mi. N of Salome Highway
    Gladden 5170 2198 4.06 US 60 at Gladden, 34 miles W of Wickenburg
    Additionally, a significant flash flood event impacted the Wickenburg AZ basins where 3-4 inches of warm coalescence rain fells in ~1-3hrs from a decaying feeder band of Nora. Should be an significant weather/rainfall event for the state and Pima County appears to be in the early crosshairs for it. The early model runs of both the Pacific trough and Newton suggest some complex prediction decisions will occur over the next 24-72 hours. Interesting, Jack