Monday, July 31, 2006

Flooding on the Rillito 31 July 2006 -- Tucson

I've put together a webpage with videos and historical peak discharge information related to the Rillito Creek flooding of 31 July. CLICK HERE to see it. Hopefully, a meteorological analysis of the storms /MCSs that led to this event will appear in a future post by Bob.

P.S. For you flood-o-philes out there, July 31st is also the 3oth anniversary of the Big Thompson Flood in Colorado which took place 7-31-1976.

Sunday, July 30, 2006

If I ran a weather service

I found another anonymous post on the blog today - we are modifying the headers to make it clear that anyone who posts needs to identify themselves, so that everyone knows who is talking to whom. Our earlier post of this requirement became lost far down in the list of posts. I do want to respond to these comments, even though we do not know who made them.

Anonymous said...

"Perhaps the pops are an artifact in the forecast as the NWS does more important things than update the 60 % to 100%. Any idiot can see its raining."

I understand that the NWS does far more important things than generate routine forecasts for the next seven days. I also understand that, to NWS management at many levels, getting the mundane products out on time seems to be almost as important as getting a warning out before a life-threatening event occurs. If I ran a weather service, the emphasis would always be on getting the immediate and critical products out to the users and customers. I would also have a "caution sign" posted and broadcast for the customers stating: "Because of current severe and/or life-threatening weather, production of routine products has been temporarily suspended. Routine services will resume when the current threat has ended."

"Effort spent updating the forecast, possibly taking away resources from some other, more important task in the NWS office would be foolish."

I agree. In fact, while I was writing the post that was commented on, the forecast staff at the Tucson office had recovered from the early am crises and were amending the morning forecast. They were willing to amend, probably since the window view was obviously different from the forecast, and tackle all the onerous grid-modification work required of a first period forecast change. Kudos to them!

But, I do have a much longer-term concern about weather conditions and the first period forecast, or short-term forecast or whatever, being obviously out of sync. I have observed this situation far too often, in far too many places, and in far too many kinds of weather situation not to feel very bothered about the overall situation.

"Furthermore, even if the NWS did update the forecast, many media outlets would continue to read the old forecast. They don't check for updates every time it is read."

This isn't a generic aspect of the media. One thing that has disturbed me deeply over the years is to listen to media ridicule the NWS because a forecast has obviously gone awry, as per: "That's the forecast! Don't those guys have a window over there?" Heard on the radio in Norman, OK, on a morning when the forecast was for sunny but the skies were heavily overcast.

"You are worrying about things that simply don't matter when there is actual life threatening flooding occurring. I fail to see how your commentary on this matter is at all productive?"

I agree again, but think that the NWS offices should make it very clear to its customers when the focus has shifted away from the standard routine, and I think NWS management should support its line staff to decide when routine procedures and products should be dropped temporarily, as per my thoughts above.

Friday, July 28, 2006

Unusual Tucson weather

Yesterday was quite an unusual summer day. The high temperature was 85F - pleasant, but humid, relief from the heat wave of a few days ago. Most unusual was the occurrence of the high temperature at midnight as the day began. The high temperature during the day reached only 83F - considerably cooler than the lows over the past weekend.

Another nocturnal MCS moved across southeastern Arizona early this morning. Lightning and thunder here at the house around 2 to 3 am with 24 hour rainfall of 0.39" (0.06" of that occurred before noon yesterday morning). Lightning and thunder at Davis Monthan AFB around same time but, as is typical, no significant convective weather was observed at Tucson International Airport.

The Rillito wash has been running bank-to-bank during past 24 hours, as have most washes - stupid motorists water rafting in SUVs and other typical craziness that attends heavy storms down here abounds.

Thursday, July 27, 2006

Help - someone explain NWS POPs to me

Could someone please explain what exactly the POPs in this morning's NWS forecast mean?

Driving in to the university, in steady light to moderate rain, I heard the following forecast on NPR for the Tucson area.

Today: Mostly cloudy. Numerous showers and thunderstorms early in the morning...then scattered showers and thunderstorms. Highs 87 to 92. West wind 5 to 15 mph. Chance of precipitation 60 percent.

This is still the forecast at 9:30 am for the Tucson metro area, even though it has been raining across the metro area since 1200 UTC. The NPR forecast was followed by news about the roads that are currently closed due to flooding washes. The observations at TUS (verification point for the forecast) since 1200 UTC have been:

Day Time VSBY WX 1hr precip

27 Jul 8:55 am 10.00 -RA 0.02

27 Jul 7:55 am 10.00 -RA 0.04

27 Jul 7:30 am 3.00 RA

27 Jul 6:55 am 10.00 -RA T

27 Jul 5:55 am 10.00 -RA 0.01

27 Jul 5:10 am 10.00 -RA

27 Jul 4:55 am 10.00 -RA 0.07

Perhaps the POPs mean that when the current rain stops, then there will be a 60% chance of more rain later today?

Or, perhaps I just don't understand how the NWS defines and uses POPs anymore.

Another large MCS over Arizona!

For the second night in a row a large MCS has developed over Arizona, this one developing late and continuing active at sunrise.

I've attached several images: CLICK HERE

Fig 1 - IR image 0200 Z 26 Jul - This image shows three distinct MCSs, at least in the satellite view, that would force new convective development as their gust fronts converged over Phoenix.

Fig 2 - IR image 0630 Z 26 Jul - This image shows the resultant, huge cold cloud shield covering much of Arizona. The interesting thing about this MCS is that radar views indicate that 3 or 4 distinct smaller MCS are propagating a variety of directions beneath the over-arching anvil cloud. One of these actually moved eastward from the Phoenix Valley up into the Salt River drainage.

Fig 3 - A map of CG lightning strikes from 12z 25 Jul to 12z 26 Jul. The CG locations are color-coded by time. Close examination of the timing of the CGs also indicates the different propagation movements beneath the cirrus.

Thus, this was a conglomerate MCS with much internal sub-structure and no long-lasting leading edge convection, or consistent motion due to propagation. This event appears somewhat similar to what Blanchard (Bull. Amer. Meteor. Soc., 71, 994-1005) terms a "chaotic MCS," see for example his Fig. 6.

Fig 4 - IR image 12Z 27 Jul - This image shows a sunrise MCS that developed near midnight last night just ahead of a distinct 500 mb circulation moving southwestward within the larger- scale anticyclone that is over the Southwest. It is almost as impressive as the MCS on Tuesday night. This MCS, however, did exhibit leading convection/trailing stratiform through much of its life and has also propagated steadily toward the southwest. A pleasant morning surprise to find light rain falling and rain in the gauge again (0.17" is all). As the MCS came overhead, no thunder or lightning was observed at TUS - in marked contrast to the observations at David Monthan AFB, and also at our house.

Fig 5 - Catalinas photo at 1300Z 27 Jul - view of the Catalinas taken through light rain at about 6am this morning.

Yet another interesting day, thanks to the great moisture surge produced by Tropical Storm Emilia on Monday night.

Wednesday, July 26, 2006

Brief comments re yesterday and last night's storms

The influx of low-level moisture, triggered by Tropical Storm Emilia, produced very unstable thermodynamics over much of Arizona yesterday. CAPE values were about as high as we see out here, but there was also considerable CIN to overcome at low-elevations. Indeed, the Phoenix region became the eventual focus of storm action after dark last night.

While the atmosphere was very unstable for convection, the winds were quite light below 500 mb and there were no distinct steering flows, nor much in the way of wind shear within the lower half of the cloud-bearing layer.

Storms developed over high terrain in three regions: 1) east to south of Tucson and 2) north to northwest of Phoenix during mid to late afternoon, and then 3) northeast of Tucson/east of Phoenix during the evening. The three resultant MCSs produced outflows that converged into the Phoenix area shortly after dark.

The MCS south of Tucson was characterized by storm cells that seemed to move randomly in a variety of directions, before eventually drifting to the west. Some of these produced hail - see

The late MCS (number 3) produced a great lightning show between 9 amd 11 pm here in Tucson, but, alas, not much rainfall.

A final, congolmerate MCS formed directly over Phoenix as the gust fronts converged there, produced torrential rains, and drifted slowly westward during the night.

Outflows from the massive convective episode did not reach to Yuma. Because of the slow movements and lack of a long-lived, dominant outflow driving westward propagation, I would not call this event a tropical-like squall or desert derecho.

I took four photos - CLICK HERE - from the house. Two of these show my rain gauge at noon yesterday and then at sunrise this morning. The third photo shows a dusty outflow moving north across the Catlina Mountains toward Phoenix late afternoon yesterday, and the last shows stratus cloud along the flanks of the mountains this morning.

The PHX and TUS soundings are quite stabilized this morning from all the activity yesterday. The Tucson area can usually recover more quickly than can Phoenix - this should be especially true for this event, since rain amounts around Tucson were not great (0.14" here at house, Trace at both TUS and DMA).

My initial impression is that neither the NAM nor WRF forecasts forecast the complex evolutions of storm complexes that actually occurred.

More later on this event!

Tuesday, July 25, 2006

Another hot day yesterday - then low-level moisture!

Monday July 24, 2006, was yet another hot and dry day for southern Arizona. Links to two newspaper stories on the heat in the Southwest are:

Monday's reports - Phoenix had a high of 114F with a late evening, high-based thunderstorm producing wind, dust, and a trace; Yuma had a high of 114F with no rainfall; and Tucson had a high of 108F with yet another day of very suppressed convection.

The good news is that moist, low-level air surged into most of southern Arizona during the night. So, temperatures will moderate some but at the cost of higher humidities. I think all of us here in southern Arizona hope that the higher humidities will bring increased storms and rain!

Sunday, July 23, 2006

Emilia and surge of moisture into Arizona

Emilia is aproaching 20 N and 110 W this evening. She is moving into the region where I've observed that Tropical Storms and Hurricanes usually trigger a significant surge of very moist air northward up the Gulf of California.

I've posted three images - CLICK HERE - the first shows IR imagery of Emilia at 2030 UTC on the 23rd, the second shows IR imagery of Emilia at 0100 UTC on the 24th, and the third shows the current NHC forecast for Emilia. I've highlighted, in light green, what I consider to be the critical region that a tropical system must move through to trigger a northward surge of moisture up the Gulf of California. The latest IR image shows that Emilia has an eye and that it is approaching this critical region. Current observations from La Paz and Mazatlan indicate that such a surge may have already begun at the south end of the Gulf. Operational forecast models are usually very slow in their forecasts of such an event.

I expect that a surge of high dewpoint air will likely arrive at Yuma, Arizona, as soon as 1400 UTC tomorrow morning (and if not by then, within the ensuing 12 hours). The surge event triggered by Emilia will be hard to differentiate clearly from the outflows likely from two significant MCSs that are also moving over the Gulf of California this evening - see the most recent IR satellite image.

Regardless, it appears that the next couple of days will be far more interesting than the past several!

Saturday, July 22, 2006

Tropical Storm/Hurricane Emilia on the horizon

It is interesting that the NHC now forecasts Emilia to move north of 20 degrees N as a hurricane at 11 pm on Sunday night. The position of Emilia north of 20 and south of Baja is nearly perfect (assumimg that the NHC forecast is reasonably accurate) for the storm to trigger a significant northward surge of moist air up the Gulf of California. I am not sure why, but neither the NWS PHX nor the NWS TUS forecast discussions today have even mentioned that Tropical Storm Emilia has formed, much less that she might have significant impacts on Arizona within the next two to three days. Regardless, a return to more moist conditions would be much welcomed at my house after the desiccating, dry east winds of the past two days!

Deja vu - two more days with strong east winds

Yesterday and today (Friday and Saturday, July 21 and 22) were again dominated by strong east winds and low dewpoints. I have written a brief blurb about this situation and included several figures illustrating yesterday's very suppressed conditions here in southeastern Arizona.


More on haboobs

Roger Edwards posted a comment on the July 18th haboob in southern Arizona. He included a link to a url documenting a haboob in west Texas. CLICK HERE to get to this site.

Friday, July 21, 2006

More on surface weather observations at NWS TUS

I am just begining to draft a paper on the state of surface weather observations at the NWS observation site at Tucson International Airport (TUS). This document will reside on the MadWeather web page, but I will post alerts here on the blog as I add new information.

Initially, there is a figure on the web page that shows annual thunderstorm days observed at TUS versus annual thunderstorm days observed at Davis Monthan AFB (DMA). Note that TUS and DMA are spatially separated by only about 8 km.

CLICK HERE to view the figure of thunderstorm days per year for 2001-2005.

This figure leads to an obvious, and very important, question: What happened after 2001?

This topic continues that posted on the blog earlier as: "Where have all the thunderstorms gone?"

More to come.

Thursday, July 20, 2006

The NWS short-term forecast yesterday afternoon

There were strong and heavily raining storms over the far northeast and east sides of the Tucson metro area last evening. These storms tried to move into the lower elevations of town but were not very successful. I was in the north foothills with an excellent view of all the metro area, except the far northwest. I also had the car radio set on the NOAA WX Radio band. At about ten after 7 pm, a short-term NWS forecast produced around 5 pm was still being broadcast. This forecast alerted listeners of heavy storms that were moving toward the valley and noted that these storms were expected to remain mainly to the south of the city. At the time this was playing, I was in a thunderstorm with light rain on the north side; could see R+ to the east of my location and also a heavy cell on the far east side of town that had produced a downburst and lots of blowing dust. There was also a brillant double rainbow arcing over the east side of Tucson (my digital was at the house!). The west edge of these storms is visible in this 7 pm web cam photo . Note that the camera view is to the north from the Computer Sciences Building on the University of Arizona campus.

My point here is - Since the 1970s, I have always felt that if we can't accurately tell the public what's happening right now, why would we expect them to have much confidence in our forecasts. My first rants on this subject were made after I was driving into Boulder in heavy wet snow (about 3 to 4 inches had accumulated already in Louisville, Colorado) on my early morning commute. The official NWS forecast playing on the radio was for rain and thundershowers, possibly turning to snow by evening. This experience in Colorado happened on a May morning almost 30 years ago, and by the time the event ended I measured 34 inches of snow accumulation in my back yard.

The storms of Tuesday July 18, 2006

The storms that occurred on the afternoon of July 18th were probably the most severe that have affected southeastern Arizona so far in July. There were no severe storm outlooks or watches issued for southeast Arizona on this day, although the local NWS Office was very busy issuing warnings for dust, severe storms and then flash flooding.

We were in Phoenix most of the day and during our drive back we saw and experienced some very wild weather. Car thermometer was registering 114F as we left Phoenix. As we were approaching Picacho Peak, a strong tstm cell off the north end of the Picacho Mountains threw out a macro burst/haboob that moved from northeast toward the southwest. When we got to this duster the visby was only down to 1 to 2 miles across the interstate. However, a very intense storm somewhere to south of Marana, over the Avra Valley, produced a huge haboob - CLICK HERE to see two photos we took as the dust cloud approached, also shown is a web cam photo of one of the storm cells over north Tucson at 5 pm MST. The haboob photos were taken at about 4:20 pm near Red Rock, Arizona, from the shoulder of I-10. Visby went to zero for a short period; wind gusts from the south were in the range 40 to 60 mph; there was chaos on the interstate; and there was a five car pile-up just down the way from us. During trip back to Tucson temperature ranged from 114F on south side of Phoenix to 76F just north of Tucson. Only 0.10" in the rain gauge here at house. But, I guess that I should leave town more often, since my presence seems to be a strong suppressant!

Tuesday, July 18, 2006

More postmortem details for 15 July

I have written a short postmortem of weather, or lack thereof, over southeastern Arizona, with graphics, for Saturday July 15, 2006. It can be found on the MadWeather homepage:

Sunday, July 16, 2006

Another postmortem needed!

The weather events of yesterday really need a fairly detailed postmortem analysis. The e-mail buzz was about how big a day it would be in southeast Arizona; the local forecast had 40% POPs (as high as they've gone this summer I think); there was a severe thunderstorm watch issued for much of the southern third of the state (the 4th watch this year I think). What happened? There were intense storms over much of south central and southwest Arizona, while the southeast portion of state was very suppressed. There were 4 severe storm reports that were in or near the western half of watch area and the eastern third of watch was devoid of thunderstorms even.

What happened with such an outwardly "good" situation? The primary bugaboo seems to have been that the approaching sysnoptic scale system was strong enough to "override" the diurnal boundary layer flow regime, bringing pronounced downslope, drying, boundary layer winds to southeastern Arizona. Note that terrain elevations decrease from over 7,000 ft msl at the Continental Divide in southwestern New Mexico to about 2,500 ft msl in Tucson area.

In some ways yesterday was somewhat similar to events aassociated with TS Nora several years ago - much precipitation expected but none realized due to the strong east winds in low-levels. Interestingly, Nora is often referred to locally as "No rain at all."

I hope to post a numbe r of graphics and more discussion about July 15th later today.

Saturday, July 15, 2006

Postmortem of yesterday's "forecast"

One of the most important aspects of weather forecasting is (or used to be) doing routine postmortems of what went wrong yesterday. The storms in southeast Arizona yesterday (Friday, July 14 2006) did not evolve as I had expected. I had anticipated a late afternoon, large MCS event with some significant rains and winds across the Tucson metro area.

What went wrong: First, I made a novice kind of mistake by finalizing my outlook before all the observations were available. (Note that I forecast mostly using the basic observations and then may use model progs to cross check details of what I'm anticipating.) Yesterday's morning sounding that eventually arrived from Phoenix NWS/SRP showed a considerably drier lower-half of the atmosphere than did Tucson's and that advective winds were pointed toward Tucson. So, during the day that deep layer of moisture that was sampled by the TUS morning sounding gradually vanished, particularly between 700 to 500 mb. Thus, much of the day in southeast Arizona was markedly suppressed. It's not an irrelevant question to ask: "Where did that low-level moisture sampled by the Tucson sounding go?"

However, storms erupted near dark, producing a great lightning event, and I see there were a couple of severe reports around 10 pm. Two small MCSs raced west-southwestward during the night, so the outlook was not a total bust.

Looks like the drying we suffered yesterday was advecting from the higher terrain to north/northeast and mixing down - evening soundings at PHX and TUS were much different than in the morning. The TUS evening sounding remained very unstable but needed substantial mesoscale kick to lift moist part of BL air to LFC. (The 00Z TUS sounding shows an excellent example of how very strange boundary layer structures can sometimes evolve out here.) Davis Monthan AFB and TUS international airport both got measurable (TUS 0.30") and DM had gusts to 52 mph - lightning show was spectacular from the house with lots of thunder - note that once again a storm went right over the TUS airport and there was no tstm observed there (one TUS ob had the added remark "distant lightning SE-SW"). Not even a trace here, as is so often the case.

Next couple of days will be dominated by the huge, upper-tropospheric cyclone that's coming westward across northern MX (note there were a couple of impressive MCSs moving westward from TX Panhandle into NM last evening!). Our big day better be today - there's substantial cooling below 500 mb and lots of upper-level moisture coming with this not-at-all-subtle system. So I expect some substantial changes while we're under the influence of this large-scale system.

I note the following in the TUS morning forecast - POPs go to 40% for tonight and tomorrow night but are 30% for all other periods for next 7 days - high temps are forecast in the range 99 - 108F for entire 7 days with today and tomorrow being hottest (today 103 to 108 and tomorrow 100 to 105). I suspect that we may well deviate much more from climatology than this forecast does.

Should be another couple of interesting weather days!

Friday, July 14, 2006

Weather outlook 14 July 2006

Yesterday was an interesting weather day in the Tucson area. A very intense storm developed mid-afternoon on the east end of the Catalina mountains. Thunder observed at our house, but storm moved to southeast; split into 3 cells and dissipated. Apparently the steering level flow began to strengthen and become more easterly, since strong storms east and southeast of Tucson began building over the metro area before dusk. These storms produced lightning, thunder, light showers, and dusty east winds with gusts around 30 kt. Davis Monthan AFB observed thunder and measureable rain; TUS observed a rainshower, a trace of rain, and carried a CG remark on one observation; here at the house I observed thunder for the second time during the day, along with a dusty sprinkle, outflow winds, and a trace of rainfall.

Today, Friday July 14, appears to have all the ingredients coming together for a newsworthy significant thunderstorm day over southeast and south Arizona. Significant moisture and CAPE remain in place; steering level winds are from east to east-southeast at 15 to 20 kt; upper-level winds are from the north so that anvils should spread off to left and behind any organized storms that develop; middle-level temps have cooled about 3 to 5 degrees; BL temps will be very hot encouraging strong outflows; and finally the wind profile has the potential to support tropical-like squall line/MCS moving toward the west. I anticipate a much more interesting day today and will keep my digital camera handy!

Thursday, July 13, 2006

Gulf Surge Index on-line at Creighton Univ.

Art Douglas, Creighton University, computes a real-time Gulf Surge Index (GSI) daily. The index is computed from the surface data observed hourly at Yuma, Arizona. Values less than 10 index no surge detected, values greater than 10 indicate a surge event, and values of 60 or greater indicate a major surge event. Values for 2005 and 2006 to date are at:

For the past week: no surge events July 6 - 9. Surge events with values in range of 10 to 20 have occurred on July 10, 11, and 12..

The slow increase in moisture has lead to a situation over southern Arizona where high values of CAPE have developed at the same time that boundary layer temperatures have increased. The TUS sounding this morning is quite potent, but the winds aloft are weak. There is likely to be a dramatic increase in storms today, despite the NWS current POPs of zero for the local Tucson area.

Tuesday, July 11, 2006

Where have all the thunderstorms gone?

On Monday the 26th of June, Katie and I flew from O'Hare back to Tucson, arriving at dusk. In route from DFW the pilot came on the intercom and said that Tucson was reporting some light showers in the area. We had a very long and turbulent approach because of a last minute runway change as a strong gust front moved over the airport. The weather during the landing was a thunderstorm with light rainshower (my observation - NOT the official TUS observation!) and strong winds from the east.

About a year and a half ago I circulated an e-mail commenting on the dramatic decrease in thunderstorm events that had occurred in the official NWS current weather observations at Tucson International Airport since 2001. A number of people in NOAA and other organizations expressed concern, but the observations seem not to have improved at all. I feel that inaccurate current weather observations at TUS constitute a real and serious threat to aviation operations. Of course, the climatology of thunderstorm events at TUS has been badly distorted also.

I have just taken a look at the July 2006 observations to date at both TUS and also at DMA (Davis Monthan AFB). These two surface observation sites are separated by only about 8 km. During the first 10 days of July the current weather observations at TUS indicated that two thunderstorms had occurred at the airport, while the observations at DMA indicated that nine different thunderstorms had occurred at the air force observing site. Thunder was reported on two different days at TUS but was reported on six different days at DMA.

Perhaps the most interesting observation at TUS this month occurred when rainshowers with gusts to 51 mph and visibility of 2.5 miles (in HAZE!) were reported on the Fourth. During the same period at the nearby AFB, a thunderstorm was observed continuously for well over two hours.

I will be gradually preparing a paper focused on this topic at the new website that Katie and I are setting up. I will link to the paper from the blog as figures and expanded background are posted on the website.

Anatomy of a monsoon storm

The following link connects to a newspaper graphic that purports to explain monsoon thunderstorms.

It's the kind of thing that one might ask an intro class: "How many things can you find wrong on this page?" The focus on cold fronts is interesting, since most of us would love to have some really good cold fronts come by during our summer heat!

As for the box at lower right "This week's forecast:" I had no precipitation at my house (sadly one of the driest locales in the metro area) on "Today" - June 28th, but did hear thunder from a storm on the Catalina Mountains. On Thursday, Friday, and Saturday I observed both thunder and precipitation at the house.

Monday, July 10, 2006

Examples of the use of lightning data at SPC

David Bright has posted a comment regarding the use of CG lightning data at SPC to evaluate their experimental "enhanced thunderstorm outlook." The hyperlink to the examples is:

Sunday, July 09, 2006

Photos of Friday's Heavy Storms

Heavily raining thunderstorms struck central Tucson during the midafternoon on Friday, 7 July.

The following link is to a newspaper story covering the event. Embedded in the story is a link to a slide show of storm-related photos taken on Friday.

Thursday, July 06, 2006

Could NWS use high-tech observations more effectively?

Art Douglas has posted several comments - in one of these he makes what seems a perfectly reasonable suggestion that the NWS consider using areal observations from high-tech observing systems that are routinely used by forecasters and researchers. He suggests considering radar-estimated rainfall and CG lightning strike data to determine when the monsoon has arrived where. The advantages over using a single point observation seem obvious. This, to me, seems a reasonable suggestion, but it also raises a very important question and issues related to how the NWS uses observations.

Consider that:

The new WSR-88D doppler radar system has been operating nationwide for more than a decade. The radar processing systems routinely produce maps of radar-estimated precipitation accumulations.

The CG lightning strike detection system has been operating nationwide for about two decades.

The satellite observing systems have been in place, and continuously improving, since the early 1970s. Satellite rain estimation techniques have been used by researchers and the NWS for more than two and a half decades.

It seems clear that the NWS could draw upon observations from these systems to define better the onset of the monsoon.

But, the larger question is: Why doesn't the NWS use data and products from any of these systems (systems whose cost to the nation has been at least in the tens of billions of dollars) to verify, assess, or crtically evaluate their forecast products?

For example, the SPC could routinely use CG lightning strike data to evaluate the reliability of their thunderstorm outlooks.

Satellite and radar products could be used to evaluate what actually happens relative to point weather observations and etc. etc.

If anyone knows more on these issues, please share your information with us.

Note - now that I've thought about it a bit more, it seems that the NHC might make more quantitative use of the satellite data in assessing their forecasts than other components of the NWS.

Sunday, July 02, 2006

A clarification

The second comment of a technical nature came in yesterday - from "anonymous."

I guess that we should have specified some ground rules for the blog. Public discussion, regardless of the topic, is not very effective if we don't know who is talking to whom. This, of course, is why newspapers and magazines don't publish letters unless they are signed.

I don't know how things work in the general blogger world, but MadWeather will not accept unsigned posts in the future. We will leave the current "anonymous" post up on the blog, since we had not addressed this issue before it was posted.

I would suggest, if someone has comments but doesn't want to identify themselves, that you contact me directly.

Saturday, July 01, 2006

Monsoon "officially" arrives at Tucson

The 2006 monsoon has "officially" arrived at the NWS surface observation site at Tucson International Airport (TUS) as of Wednesday 28 June. Has it arrived at other places in southeastern Arizona, and if so when? There is no clear answer to that question, assuming anyone is actually interested. I can not resist pointing out several things.

Using the NWS Tucson definition for the official start of the monsoon, it appears that the monsoon arrived at Davis-Monthan Air Force Base one day earlier than it did at TUS. These two surface observing stations are less than 10 km apart.

If one used other definitions of the "start" of the monsoon, the dates of arrival would vary considerably.

For example, if the start at TUS were defined as the first time that the running three-day average surface dewpoint temperature exceed 50F, then the monsoon would have begun on 6 June.

If we defined the start of the monsoon in Arizona as the first day on which the count of cloud-to-ground lightning strikes across Arizona exceeded 10,000 (a fairly significant number of strikes!), then the 2006 monsoon would have begun on 8 June.

Enough said about the Arizona monsoon conundrum for summer 2006!