Sunday, June 17, 2018

Great Precip Event For Mid-June!

After the synoptic pattern transitioned to a westerly trough interacting with residual Bud moisture (e.g., a pattern more typical of Fall transitions) early yesterday, there was considerable thunderstorm activity across much of the area. The trough moving across our region produced much more rainfall that did the first part of event when the Bud moisture intrusion occurred. Here at house we had only 0.23" inches of rain for period ending at 5:00 am MST yesterday, but a total of 0.93" by time last storm of day at 6:00 pm. The total for the event at DM AFB was an impressive 1.42".


The view from campus yesterday looking north toward Catalinas captured a heavy thunderstorm coming into the north metro at 5:00 pm. The nearly concurrent KEMX base scan (below) indicated an arc of heavy storm echo crossing I-10. This storm collapsed over the north potion of city, producing a wet downburst. We were near River and campbell, where winds of 40 to 50 mph occurred from the south - at same time TUS and DM reported gusts from north of 25 to 30 mph.

Second below (from WeatherBell and Vaisala) shows CG flash density for 24-hours ending at 7:00 am this morning.




Two snips from ALERT precip totals for the event (these are quite hard to read - no matter how close I zoom in the actual data icons remain tiny); however the white/red icons indicate more than inch amounts - which were concentrated north and east metro (above). Below shows amounts for Catalinas area.

Our June weather excitement is over as the East Pacific lobe of the 500 mb subtropical high will bring a nonsoonal pattern to the Southwest. The coming week will be dry as a rapid heat-up sets in.


Saturday, June 16, 2018

Finally Some Rain!!!!!!


Composite radar from NWS indicates a large area of showers and some thunderstorms moving into metro area from the southwest at 6:00 am MST this morning.

Rainfall here at house has gone as per: yesterday though 5:00 pm MST just some spits and sputters and a Trace; but from 5:00 pm to 5:00 am we recorded 0.23" - the most rain in gauge since middle of February! The rain began again a bit after 5:00 am and continues now. The plot of detected CG flashes below (from Atmo and Vaisala) shows 24-hours ending at 6:00 am this morning - purples to red are recent, while greens were yesterday afternoon.



The Alert network at 6:00 am this morning (north half above and south below) indicates 100% coverage (just as the models have been forecasting), with some amounts around the network over half an inch. What a wonderful event for mid-June - thanks to once hurricane Bud and the influx of moisture it triggered. The PW this am is about double the average amount for this date.



The meteorological setting is much as the WRF forecasts indicated yesterday - westerly trough moving across Arizona interacting with residual low-level moisture from Bud. The synoptic setting (12 UTC 500 mb analysis above from SPC) with the trough and westerly flow regime is distinctly "non-monsoonal" today. The morning sounding from TWC (below - also from SPC) indicates moderate CAPE, with westerly winds through troposphere from 700 mb up, and residual moisture from Bud extends up to 500 mb. The setting today is very much like a Fall transitional pattern. The evolution of the cold middle-level pocket of air coming by and any local heating that might occur will determine how intense local thunderstorms are - the morning sounding looks a bit like a wet microburst setting - we shall watch and see!


Friday, June 15, 2018

Showers And Heavy Clouds This Morning


Have to leave shortly to pick my son up at airport - so just a brief look at our interesting situation. Heavy middle clouds cover most of southern Arizona this morning (as per view from campus above) and they produced a few light sprinkles during early morning hours - hard to tell if we had a Trace here, but there were some widely spaced drop splats in the dust along Allen, just north of here. Current radar indicates sprinkles and a few showers across the metro area.


The 06 UTC WRF-GFS runs appear to have captured the cloudiness quite well, and I'll take a look at a few forecasts from that model run at Atmo. Forecast above is OLR at 8:00 am MST this morning - while second below is same forecast but for 3:00 pm this afternoon. Model forecasts little solar heating for the day - which is quite warm already (82 F at 6:30 am here at house).

Immediately below is the forecast skewT for TWC valid at 3:00 pm this afternoon. The sounding has PW over an inch, but lowest levels continue somewhat dry. While the forecast indicates mixed layer CAPE of only a bit over 250 J/Kg. The sounding is not very exciting, unless some clearing and heating happens during mid-day.




But, the model's forecasts for tomorrow are actually much more interesting. The low-level remnants of Bud head off toward southwest New Mexico, while Arizona is mostly affected by the 500 mb trough coming in from the west. The 500 mb WRF-GFS forecast above is valid at 5:00 pm tomorrow afternoon, and indicates a nice area of cold temperatures over southern Arizona and northwestern Mexico.

The forecast SkewT for TWC below is valid at 5:00 pm tomorrow (the 16th) and has mixed layer CAPE over 1,000 J/Kg, as well as a much stronger vertical wind profile (similar to a Fall transition pattern and indeed this Bud burst of moisture vanishes quickly during late day tomorrow) - but, perhaps some nasty thunderstorms around tomorrow afternoon, before the serious dry-out?

Thursday, June 14, 2018

Moisture With Dying Bud Pushing Slowly North


Mid-level buildups at sunrise this morning (with passing dove). The morning skewT for TWC sounding launched from campus (below) indicates the cloud layer nicely. Sounding remains fairly dry, especially in very deep, residual boundary layer. There may be a sliver of CAPE this afternoon from about 550 mb to around 300 mb. Temperatures in this layer appear favorable for graupel and lightning, but it is not clear whether there could be enough CAPE or vertical velocity for thunderstorms locally. The plot of detected CGs for 12-hours ending at 06 UTC last night (second below from Atmo and Vaisala) indicates thunderstorms east and south of Tucson yesterday and these should edge closer today.




TS Bud continues to weaken as it moves slowly northward. The IR image above is from 1330 UTC this morning and little deep convection remains, except for band north to northeast of storm center. The morning track forecast from NHC is shown below. The remains of Bud (which is forecast to dissipate in 72-hours or sooner) come ashore near Guaymas, Mexico after crossing southern Baja.



Even though remains of Bud appear to be veering off toward northeast and weakening rapidly, all the model forecasts have trended wetter for our area in last night's forecast runs - so a mixed bag of signals this morning. Above is again from SREF plumes at SPC page - only a few members forecast an inch or more at airport, while several forecast very light amounts. The ensemble mean is a bit over half an inch. Note that the member forecasts also show a very large time window across which the main event is forecast to occur - from the 15th to a couple of models which forecast main precipitation event on Sunday. Shown below is the 06 UTC WRF-GFS forecast from Atmo last night - model continues to forecast very significant mid-June event for all of eastern Arizona.

There are a number of uncertainties here and forecast for the metro area remains very difficult - will watch with interest to see how this all evolves.

Wednesday, June 13, 2018

TS Bud Fading Rapidly


TS Bud is weakening rapidly (IR image above is from 1330 UTC) and currently moving northward very slowly. The NHC morning track forecast of Bud's remnants continues to shift eastward. However, regardless of where old Bud circulation goes, it appears there will a nice, albeit brief, intrusion of high PW, subtropical air into Arizona. Below is MIMIC TPW analysis at 13 UTC this morning. Values over an inch are poking into southwest Arizona; however, very high PW remains south of 30 degrees north.

Note - I seem to have lost access to the Atmo weather products page, so I have no idea how the WRF forecasts are trending.

It does appear that Bud event is trending toward thunderstorms and convection rather than a widespread moderate to heavy rain event.



I've grabbed two SREF plume products from the SPC webpage this morning. Above shows QPF forecasts for TUS (note that horizontal scale lines are at 0.2" intervals above BUT 0.1" intervals below). While six members of the ensemble continue to forecast significant QPF amounts for TUS, the majority of the runs are forecasting less than half an inch - the dry members forecast only a trace to couple of hundredths. So very large range of possible outcomes continues as event draws closer.

Plot below shows trend of average TUS QPF from last 4 forecast runs (red to purple to green to blue) and are trending drier in last run (09 UTC).

Tuesday, June 12, 2018

Hurricane Bud A Category 4 Storm


Hurricane Bud has also become a Cat 4 storm this morning (sustained winds at 115 kt). Visible image above is from 1330 UTC and below is this morning's NHC forecast for the track of Bud - NHC brings the remnants of Bud directly at us.



Detected CG flashes in Mexico (from Atmo and Vaisala) inched northward yesterday afternoon (above is 12-hours ending at 05 UTC last night). First time this summer that I've seen thunderstorms occurring along the coast of the GoC. MIMIC TPW from 12 UTC (below)shows high PW once again reaching up the GoC to 30 degrees north.



Some forecast plumes shown here from the 06 UTC GEFS forecasts. Plumes for Yuma above are for PW, with very high max occurring on Friday the 15th. Below is for QPF at TUS - significant precipitation event forecast by 100% of the members, but with very large range of amounts forecast here. The same is true for Douglas - second below.



Finally a look at last night's 06 UTC WRF-GFS forecast for total rainfall through 5:00 am MST on Sunday (on 5.4 grid). This would certainly be an amazing event for Arizona were this forecast to verify. However, those who have been here for years know that precipitation associated with decaying TSs is often fickle - dominant forecast failures seem to end up with little or no rainfall even though large amounts were forecast.

Monday, June 11, 2018

Brief Update As New Week Begins


Yesterday's west winds (south of Great Basin short wave) knocked PW down to very low values. Time series of GPS PW from Atmo (above ending around 7:00 am MST) shows the drop.

The drying pushed thunderstorm activity far eastward and southward - plot below shows detected CG flashes (from Atmo and Vaisala) for 12-hours ending at 06 UTC last night.



This morning Hurricane Bud is a level 3 storm that is moving northwestward (above visible image from 7:00 am). The forecast track from NHC this morning (below) continues to move Bud to south end of Baja by Saturday. At bottom is 06 UTC WRF-GFS forecast of PW valid at noon on Friday, indicating a rather classic Gulf surge. After Saturday the models diverge with some runs holding PW high and others forecasting rapid drying Sunday and beyond.