Hurricane Newton Moves Northward Much Faster Than Forecast

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

http://arizonawrf.blogspot.com/2016/09/20160905.html

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.

Hurricane Newton And NWS Tweet

Hurricane Newton is strengthening rapidly as it heads northward toward southern Baja. The NHC forecasts Newton to be a weakening Tropical Depression, located over northern Sonora, by late Wednesday afternoon. Of concern is the very large area of moisture and convection to the north and northeast of Newton. Above visible image is from 3:00 pm MST this afternoon.

From yesterday's post, I repeat - The problem with agencies like NWS playing around in social network stuff and dumbed-down cartoons is that these media are usually too restrictive for needed technical details - what Paul Harvey used to call "The Rest of the Story."

A reader sent along the NWS Tweet below - a pretty graphic but minimal real information. I have no idea what the spaghetti plot of "tracks" is actually showing. Since one of them hits Chicago, I assume it must be the remnant 500 mb vorticty maximum left behind by Newton. I also have no idea what models all the abbreviations refer to. But, perhaps I should forward this to my sister in Chicago!

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.

Comments On NWS Tucson Weather Story Today

Here's another example, from today, of what I don't like about many NWS graphics, cartons, and "Weather Stories". The problem with agencies like NWS playing around in social network stuff and dumbed-down cartoons is that these media are usually too restrictive for needed technical details - what Paul Harvey used to call "The Rest of the Story.". 

The two images used above by TUS NWS this morning are essentially an apples and oranges mix of information regarding moisture in the atmosphere. The satellite-derived water vapor image (no units or color scale shown) is a display that provides a visualization of RH in the upper part of the troposphere - often times dry air at upper-levels lies above very moist air in the lower troposphere (obviously not so today with a morning sounding observation of PW of only about 11 mm). Key point here is that the water vapor images convey essentially no information about moisture or PW in the lower troposphere. The graphic on right is a model forecast (from which model?) of PW for some unknown time next Wednesday (no color bar shown to quantify what the colors mean). The bulk of PW in the atmosphere occurs below 500 mb. 

So, this weather story displays mostly a non-quantitative, "changing of the colors" from red to green over Arizona and New Mexico.

Here are two more quantitative examples. Above is an image from CIMSS at University of Wisconsin for one of the water vapor radiation channels. The units of this display are in radiative temperature (C). Warmer temperatures indicate drier (but not quantified) RH in upper-troposphere. The three water vapor bands usually used to create the product shown in the weather story have peak sensitivities from just above 500 mb to 300 mb. Warmer temperatures come from lower in the atmosphere and indicate little water vapor above at higher levels - thus warm colors indicate dryness.

The forecast of PW below is from the 12 UTC WRF-GFS today, on the 5.4 km grid, and is valid at 6:00 am MST next Thursday. The units are mm of PW but are displayed using a somewhat different color scale than in the weather story. The huge increase of moisture over southern Arizona is associated with the decaying Hurricane/Tropical Storm Newton (not yet named by NHC).

Summer 2016 Across The ALERT Network

The ALERT Network page (old version NOT the new version) allows one to examine rainfall totals for varying periods of interest. This is an extremely useful feature of the old software, especially for various types of research. I hope that this capability is somehow maintained by Pima County.

Regardless, I have access the rainfall totals for Summer 2016 - June 1st through August 31st and show the results here - for the sectors from north through southeast.

I assume that if there are problems at a specific gauge, the total will reflect those problems, so some degree of caution is required in evaluating these data. For comparison, here at the house our summer total was 8.89 inches - third wettest summer for my 19 years of record - while the airport recorded 5.80 inches. The variance across the network, well over 13 inches, so it's no wonder that some areas are almost jungle-like while others are barely green. More later on the summer.

Mike Leuthold noted: Bob,
I've noticed the huge variance in precipitation on my drives back and forth to Paradise. Some areas along I-10 have weeds/flowers 6 feet high while other areas are practically brown. Note the pathetic 3.62 just west of the Pima line along I-10 for example while Davidson canyon has 8.5". I don't ever recall seeing such a spotty monsoon like this in far eastern Pima and Cochise county. Usually, it's all green.

Fair Weather For Labor Day Weekend

Looking west at sunrise toward Wasson Peak in the Tucson Mountains (elevation 4687 feet MSL).

This morning's sounding plot for TWC (above from SPC) indicates warm, dry, stable conditions locally, with PW well below an inch. Only threat of showers will remain well to our east this weekend.

The PW MIMIC analysis from CIMSS at University of Wisconsin (above for 12 UTC) shows very moist, tropical air lurking at the south end of GoC. Swirl near Hawaii is Hurricane Lester, which is forecast to avoid the Islands, passing off to their north.

The morning outlook from NHC (below) indicates high probabilities for a new tropical system to develop and head north toward Baja. This system could be a player in southern Arizona weather by mid-week next week. The GEFS plumes for QPF from 06 UTC last night (bottom) forecast the possibilities of significant rains for TUS after September 7th. The operational version of the model (blue) really doesn't pick up the tropical system and has one of the driest forecasts for the coming week - in contrast to the ECMWF operational forecast, which is very aggressive, bringing the tropical system all the way to the north end of Baja. Will perhaps become an interesting second half of the first full week of September (see the Cloud-maven blog post from August 30th - link to right).

Dry-Out For Holiday Weekend

Short of time this morning, so a very quick overview. The plot of detected CG flashes above is for 24-hours ending at midnight last night (from Atmo and Vaisala). Some storms in eastern Pima County, but most activity in broad band from southeast to northwest Arizona (as per at least some of the WRF forecasts yesterday). Again there was more activity in our immediate area than forecast by 06 UTC WRF runs. Rainfall was mostly on or near the Catalinas, Rincons, and Santa Ritas, with some heavy amounts north side of Catalinas (as per 24-hour ALERT observations through 7:00 am MST this morning) below.

Blended PW for 12 UTC from CIRA (above) shows low-level moisture hanging on across southern Arizona this morning. I note that at 12 UTC the GPS PW observation for campus was 1.25", while the sounding data from there indicated 1.40" - quite a difference and I don't know if this has been impacting the WRF runs.

There is probably enough moisture and CAPE for isolated higher elevation storms again over southeast Arizona today. But, as large-scale 500 mb trough takes over the West, conditions become more hostile for storm activity. Below is 06 UTC WRF-NAM forecast of 500 winds and temperatures valid at 5:00 pm MST this afternoon, indicating very warm middle-levels over southwestern Arizona.

The longer-term forecasts indicate seriously dry air over the Southwest for the Holiday weekend. The 06 UTC WRF-NAM forecast of PW (bottom, on 5.4 km grid) is valid at 11:00 am on Labor Day. Looks like we'll have to hope for tropical activity to bring next precipitation event to our region.

Isolated Storms Again For Start Of Fall

Nice sunrise this morning to begin meteorological Fall.

There was much more storm activity over southeastern Arizona yesterday afternoon than was forecast by the 06 UTC runs of the WRF model. Appears that the 06 UTC forecasts seriously under-forecast the increases in PW that occurred during the day yesterday. Flash density for detected CGs above from weather.graphics and Vaisala is for 24-hours ending at 7:00 am MST this morning. Rainfall over the ALERT network (below) is for same period. Over the network 14 sites measured 0.04" or more of rainfall yesterday. There were sprinkles and a Trace here just after dark.

This morning's sounding (as per skewT plot above from SPC) is very moist at 1.7 inches of PW and quite unstable. However, the big question again today is how will the PW evolve with time? The 06 UTC WRF forecasts from Atmo this morning again forecast only very isolated storms over eastern Pima County and keep most activity out to the west.

Above is the 12 UTC CIRA blended PW analysis, which shows the more moist air out to our west and also indicates a small region to our south-southeast with PW less than inch. 

The 06 UTC WRF forecasts bring this dry region into play for eastern Pima County this afternoon. The WRF-NAM forecast of PW valid at 5:00 am (12 UTC) this morning above has forecast the dry region shown on the CIRA analysis. The forecast valid at 1:00 pm below expands the dry region and decreases PW here at Tucson by about 10 mm. The drying is the reason the models forecast limited storm activity in our area this afternoon. So, the key question is whether the 12 UTC forecasts will continue this drying trend.