Tuesday, December 12, 2017

Gusty East Winds Again

Very nice sunrise this morning.

Wasn't paying attention yesterday and didn't see that 12 UTC WRF-GFS on the 11th was forecasting another period of strong easterly winds. Forecast above is from 06 UTC WRF-GFS and is for 10-m winds at 11:00 am MST this morning - yesterday morning's forecast was quite similar.

Below is forecast sounding for Sonoita  from 06 UTC today and valid at 11:00 am. - it is an excellent set-up for more strong gusts at the Mt. Hopkins RAWS station with gusts well above 50 mph possible. Bottom graphic shows winds and gusts so far this morning at that site. Peak gusts at this site for last six days have been: 78, 73, 60, 45, 20, and 55 mph.

Monday, December 11, 2017

Dreary But With Mild Temperatures

Webcam views looking north around 8:00 am MST this morning show the heavy middle and high cloud cover that brought intermittent periods of gloom yesterday and this morning (top the Catalinas and below from Kitt Peak).

Another night with difficult temperatures across the metro - some spots stayed windy during the night and others had periods of calm. Lows at airport yesterday and today were much warmer than the grid point forecast - and that was just for one spot. Lows here at house for Friday through this morning have been: 27, 25, 59, and 46 F. It was quite mild at 6:00 am today when I rolled the trash bins out, but winds went calm and a clear area passed  overhead  and temperature was 10 F colder at 7:00 am. The 34 F difference in lows here between Saturday and Sunday was really huge. Atmo's WRF-GFS handled the winds and temperatures pretty well across the weekend. 

The clouds continue to roll by because of the weak, closed low (above) to our southwest, but lower-level moisture is sadly low. The graphic below shows the GEFS plumes of forecast PW for TUS. Forecasts are clustered fairly tightly through Thursday morning, but then become wildly chaotic.

Long-range global forecasts shift the West Coast ridge westward, and allow a more disturbed flow pattern for next week - but of course that's a long way away.

Sunday, December 10, 2017

Mild And Breezy Morning

Very mild this morning with 60 F here at house at 6:00 am MST. Graphic above from MesoWest shows the metro temperatures (also at 6:00 am). The WRF-GFS forecast (from 12 UTC yesterday morning) proved to be excellent - as per the model's forecast of winds and temperatures valid at 6:00 am this morning (below).

The channel 2 fire image at bottom shows that the Thomas fire in California remains very active - also at 6:00 am this morning.

Saturday, December 09, 2017

Temperatures And Winds This Morning/Snow In Mexico

Yesterday morning's WRF-GFS forecast for temperatures at 8:00 am MST this morning (above) were a bit too warm wrt the observed temperatures at that time (below). But as model trends indicated, the morning temperatures today were considerably warmer than yesterday's. The morning lows today (second below) were up some also and were reached around midnight or so, when winds dropped off. Low here at house was a bit colder at 25 F as winds stayed down. The airport had 37 F and DM dropped to 39 F.  Tonight will be another problem with the model forecast keeping winds through the night, with temperatures again warmer than today.

The winds at the Mt. Hopkins RAWS picked up again about 10:00 pm last night and have continued strong and gusty today with some hours hitting 55 to 60 mph.

Finally, a very interesting graphic was posted to the SUNY Albany MAP chat list by Brandt Maxwell (NWS San Diego). The graphic below shows snow covered area for yesterday, with a very large area of Mexico having received snowfall. Snow covered area in Mexico was greater than that over New England!

Friday, December 08, 2017

First Freeze At House This Fall/Winter

Coldest morning here so far this season - after yesterday's low of  34 F, this morning the low was 27 F. Lows around the metro area shown above from MesoWest for this morning (above), with coldest lows out to our east and south (below). Note the amazing 9 F along Highway 82 west of Tombstone. The lows at airport and DM were 36 and 33 F respectively.

Lows tomorrow morning are a difficult forecast, since winds may or may not continue through the night. The 12 UTC WRF-GFS forecasts lows to be 10 to 15 F warmer than they were today. However, that model often keeps the wind speeds a bit too strong during night - so I expect a wide-range of temperatures by 7 am tomorrow.

Winds from the east at the Mt. Hopkins RAWS site were quite strong, with max gust reaching 78 mph (below).  At that site winds gusted over 70 mph from about 10 pm MST last night through 2 am this morning (winds were over 40 mph from 10 am yesterday through 9 am this morning).  I see that winds yesterday afternoon gusted 40 to 60 mph at the 4 m telescope on Kitt Peak.

Wednesday, December 06, 2017

Sprinkle-Showers Yesterday

Sprinkles and some light showers fell across parts of metro area and mountains yesterday afternoon. there was a marginal 0.01" here at house - airport had 0.02" and DM a trace.  The ALERT network had 7 sites report 0.04" or more - mostly in mountains (below). The report from Tanque Verde Guest Ranch of 0.39 " seems high compared to nearby sites and also to the more detailed MesoWest 24-hour reports.

Sunshine has returned finally (above) and there was enough RH this morning to see your breath. Low at house was 42 F. So, a tiny weather event. Forecasts continue to indicate a strong northeast to east wind event affecting most of southern Arizona tonight into Friday morning.

In the LA  area wildfires continue to rage through parts of the city, closing freeways and burning structures. The IR Channel 2 image below shows 5 active hot spots at 15 UTC this morning. At bottom is current webcam view from LAX looking toward one of the fires (from Jack Hales "Camera Wall)".

Tuesday, December 05, 2017

Sprinkle Chances Diminishing Followed By Dry East Winds

View of Catalinas at 1539 UTC this am shows both dirty air and also that cloud bases are mostly well above the mountain tops.

The MIMIC TPW analysis for 14 UTC (above) indicates mostly dry conditions over the Southwest, with band of slightly higher values extending into southern Arizona. The 14 UTC visible satellite image (below) shows an impressive cloud deck again over southern Arizona. With dry lower levels, the model forecasts have shifted toward drier conditions, and indicate that precipitation is confined mostly to the White Mountains and northern Mexico. 

The 06 UTC WRF-GFS forecast of OLR (W/m2 - above) is valid at 15 UTC tomorrow morning has pushed the cloud deck nearly out of Arizona. So sunshine should return tomorrow, but dewpoints will plummet. As the 500 mb ridge builds southward, low-level easterly winds will develop - making temperature forecasts very tricky next several mornings.

The easterly winds become deep enough to bring a significant event to the Whipple Observatory on Mt. Hopkins. The WRF-GFS forecast sounding for Sonoita (below for 13 UTC on the 7th) indicates that winds at the Mt. Hopkins RAWS site could experience gusts of 60 to 80+ mph beginning late tomorrow and extending into Friday morning (if the forecast verifies).