Tuesday, December 10, 2019

General Precipitation Event Yesterday

View from Atmo this morning showing both clouds and fog over the city. Down at bottom is webcam view of thick fog along I-10 at San Simon, near the New Mexico border. 

Event rainfall: above from MesoWest for southeast Arizona, and ALERT data below for the Tucson metro area. Here at house we had a total of 0.68" between about 1:00 am MST and early afternoon. Two different periods with thunder and lightning. Most sites reported at least half an inch. Rain changed to snow at higher elevations, so those amounts include only the rain part of event.

Rest of week expected to quiet, with next 500 mb short wave forecast to come next Sunday and Monday, as per ECMWF forecast at second below.

Monday, December 09, 2019

Early Morning Rains

Heavy clouds over Catalinas this morning as viewed from Atmo.

Radar above was from 6:09 am MST and shows line of strong storms moving across metro area. Plot of CG flashes (below from Atmo and Vaisala) shows thunderstorm activity centered on Pima County for 24 hours ending at 7:23 AM (light pinks to white are most recent flashes).

ALERT rainfall measurements for 24 hours ending at 7:23 (second below) shows many sites with over half an inch. Only four sites had less than 0.04" and most sites over metro reported a quarter to half an inch. There was 0.48" in gauge here a bit ago.

Morning 500 mb analysis above shows short wave over the lower Colorado River Basin, about as predicted by models - perhaps a bit stronger than many forecasts last two days.

Forecasts here from 00 UTC WRF-GFS. Forecast of PW above was valid at midnight today. Rain amounts were better than I expected with the stream of higher PW coming in from west-southwest. Below is model's forecast of precipitation through 6:00 pm this afternoon.

Saturday, December 07, 2019

Update On Approaching Rain Event

Pre-sunrise view from Atmo this morning. Current morning statement from NWS below.

Above is plot of TWC morning sounding - PW up over three quarters of an inch but with three strange very dry layers below 500 mb. These are apparently real, since other soundings nearby show similar structures. The MIMIC total PW analysis for 13 UTC this morning (below) indicates PW amounts of around an inch intruding into southwestern Arizona.

GFS forecast of 500 mb winds and heights above is valid at noon Monday and indicates the short wave, with perhaps a small closed low center across Arizona. Trough axis not forecast to be as positively tilted as was forecast yesterday - a favorable change for showers here.

Forecasts for event event total precipitation amounts: above from ATMO's 06 UTC WRF-NAM and below from NWS morning statement. Note the WRF donut hole over Tucson metro. The GEFS plumes for rainfall at TUS indicate about half an inch or bit more for event. Event is developing to be considerably netter than the sprinkle showers on morning of December 4rth. 

Friday, December 06, 2019

Threat Of Showers Sunday

Nice colors at sunrise today. Above is view from Atmo on campus, and below is from Santiago Peak, southeast of Los Angeles.

The GEFS ensembles have been getting more aggressive with forecast of rainfall at Tucson - above is QPF plumes for TUS from 06 UTC members. The ensembles indicate main rainfall event from Sunday night into midday Monday. Current NWS morning forecast brings event in a bit sooner faster than the ensemble forecasts.

Above shows total PW for 5:00 am MST (12 UTC) this morning. It is currently very dry over Arizona, but there is a broad plume of higher PW along 120 W extending northward to about 30 N. The model forecasts bring this moisture eastward into Arizona - below is 06 UTC WRF-GFS forecast of PW valid at 5:00 am on Sunday morning the 8th.

The 06 UTC GFS operational forecast for 500 mb winds and heights (above) is valid at 5:00 am Monday morning the 9th. The 500 mb short wave affecting Arizona has a strong positive tilt (trough axis runs from west-southwest toward the east-northeast). Positively tilted troughs are often poor precipitation producers, since they don't force strong southerly moisture intrusions - so there's a fair amount of uncertainty with this developing event. Note that the WRF PW forecast above brings the moisture influx from the west across northern Baja.

The total precipitation forecast below is from the 00 UTC WRF-GFS and is valid from now through midnight Monday night. The forecast event is a minor one, with a few spots with around half an inch, particularly in higher elevations. Note that the amount forecast at TUS is much less than that forecast by the GEFS above. It will definitely be interesting to watch how all of this actually evolves.

Wednesday, December 04, 2019

Early Morning Showers And Sprinkles

Heavy clouds as seen from Atmo this morning at a bit before 7:00 am MST.

Some sprinkles and light showers have been moving across the Tucson metro area this early morning. Composite radar image above was at 5:27 am and IR satellite image below was at 6:00 am. 

It was raining lightly here at 6:00 am and gauge has 0.01". Amounts have been light; mostly a Trace to a few hundredths.

By 6:24 am (composite radar above) the showers had mostly moved east and north of the City. The TWC morning sounding (below) has nearly an inch of PW but is also very dry below 700 mb.

Some chances for another band or two of showers today. After the weak short-wave associated with the showers moves across the Great Basin, there will another chance for light showers around the 9th. Then it looks like a strong ridge will be dominant over the West at least into mid-December.

Tuesday, December 03, 2019

Chance For Light Showers Tonight And Wednesday

Very nice morning here in Tucson, but Pacific weather system may bring chance of showers tomorrow.

The 500 mb analysis this morning (above) shows a closed low west of California. This low is forecast to open and move rapidly eastward. The GFS forecast below is valid at midnight tomorrow night.

As the weakening trough moves across Arizona, models forecast chance for light showers. The forecast above is from the 12 UTC WRF-RR and shows forecast precipitation amounts through noon on Thursday. Amounts in the forecast are very light, with nothing indicated for the airport. The QPF plumes from last night's GEFS forecast runs (below) also indicate chances for very light showers, with the ensemble average (black) indicating about 0.05" inches at airport.

Quite a change from today, but certainly not a significant event according to latest forecasts.

Sunday, December 01, 2019

Travel Misery After Thanksgiving

Above - traffic jam heading into LAX this morning.

Below - map showing delays at major airports - looks like NYC and MSP have worst delays currently.

Bottom - bird feeder somewhere near Duluth.

Happy not to be travelling today.