Someone asked me if my use of "spitting rain" was a technical term and, if so, what does it mean?
Obviously, it's not very technical, but here is my attempt at a definition.
Subjective - if it is spitting rain, you can almost run between the drops.
More quantitative - if you observe spitting rain falling onto a porous surface, such as concrete or flagstone, you'll note the following. The drop splats and wet spots remain separate from one another while it is spitting rain. If the surface becomes completely wetted, then light rain, or heavier, has begun.
So that's it - not copyrighted; feel free to use.
Watch a video (Madweather's first attempt at doing this!)
Saturday, July 05, 2008
Storms in Tucson on the Fourth of July
While the central and south parts of the state were very active yesterday with several severe storm reports, the nearby mountains here were suppressed relative to the day before. The boundary layerby late afternoon was only well-mixed in moisture up to 600 mb. This layer required substantial lift for its CAPE to be released.
A strong cluster of storms near Green Valley produced a deep outflow that was visible on the KEMX base scans. It passed TUS at 6:46 pm when winds shifted to the south with gusts to 38 mph. Thunderstorms were developing along this outflow as it moved north across the city. We had thunder and light to moderate rain here at house from about 7:00 to 7:40 pm with total rainfall of 0.35". The lightning was quite spectacular with CG bolts jumping out to the north of the cells through clear sky. Quite a dangerous situation.
Significant moisture remains in place but winds aloft over southeastern Arizona are becoming nearly light and variable in the NAM forecasts through midnight. My guess is that this afternoon's well-mixed, in moisture, boundary layer will have theta w of about 24C - a very favorable value for moderate CAPE and heavy storms. But the situation will probably be like yesterday and the air mass over the deserts will require a good kick from outflows from storms at higher elevations. Timing will depend on heating and how quickly storms develop over higher elevations. Also appears as if the northwestern half of state will have an active day.
A strong cluster of storms near Green Valley produced a deep outflow that was visible on the KEMX base scans. It passed TUS at 6:46 pm when winds shifted to the south with gusts to 38 mph. Thunderstorms were developing along this outflow as it moved north across the city. We had thunder and light to moderate rain here at house from about 7:00 to 7:40 pm with total rainfall of 0.35". The lightning was quite spectacular with CG bolts jumping out to the north of the cells through clear sky. Quite a dangerous situation.
Significant moisture remains in place but winds aloft over southeastern Arizona are becoming nearly light and variable in the NAM forecasts through midnight. My guess is that this afternoon's well-mixed, in moisture, boundary layer will have theta w of about 24C - a very favorable value for moderate CAPE and heavy storms. But the situation will probably be like yesterday and the air mass over the deserts will require a good kick from outflows from storms at higher elevations. Timing will depend on heating and how quickly storms develop over higher elevations. Also appears as if the northwestern half of state will have an active day.
Friday, July 04, 2008
Interesting Weather Continues in the Southwest
Weather Update - 8:00 am Friday July 4, 2008
Yesterday was a very active day with most reporting stations in southeast and south central reporting thunderstorms and wind gusts of 30 mph or greater. Douglas reported a gust to 75 mph, and others of note were: 53 at Mt. Hopkins RAWS, 45 at Scottsdale airport, and 44 at TUS. The Pima Flood Control District monitors rainfall at 91 sites in eastern Pima County and 56 of these sites reported measurable rain for the 24 hours ending at 6 am this morning. Notable amounts: 4.61" at Manning Camp in the Rincons (this is from a RAWS site and may be suspect) and 1.77" at Oracle Ranger Station. The most rain reported in the main part of the City was 0.47" at Pantano and Houghton. Of the 18 City gauges only 6 reported measurable rain, showing that the higher elevations did much better. Here at the house we had lots of lightning and thunder, several outflows and a couple of brief spits of rain, amounting to a trace. But the cool outflows and strong smell of rain made for a great evening.
This morning the moisture contents over southern Arizona have continued to increase. The TWC sounding is very moist and indicates the most CAPE present for the season so far. The IPW products and surface observations show that the surge of GoC moisture which began midday on Wednesday has pushed north almost to Las Vegas. IPW at Tucson is 38 mm this morning and Phoenix has 41 mm.
Winds in the upper and lower troposphere are light and variable, but steering level winds from 400 to 600 mb are from the east-northeast at 15 to 30 kts. There are no synoptic features of note today, except for the moderate wind flow around the midlevel anticyclone and perhaps a bit of midlevel cool advection. Expect that it will be another active day across much of southern Arizona. With higher moisture and lower cloud bases, the threat of heavy rain is greater today and the possibility of severe downbursts remains significant. The increased CAPE will allow better propagation of mountain storms into the deserts during the afternoon and evening.
So, another active day likely with lightning fireworks for the Fourth.
Yesterday was a very active day with most reporting stations in southeast and south central reporting thunderstorms and wind gusts of 30 mph or greater. Douglas reported a gust to 75 mph, and others of note were: 53 at Mt. Hopkins RAWS, 45 at Scottsdale airport, and 44 at TUS. The Pima Flood Control District monitors rainfall at 91 sites in eastern Pima County and 56 of these sites reported measurable rain for the 24 hours ending at 6 am this morning. Notable amounts: 4.61" at Manning Camp in the Rincons (this is from a RAWS site and may be suspect) and 1.77" at Oracle Ranger Station. The most rain reported in the main part of the City was 0.47" at Pantano and Houghton. Of the 18 City gauges only 6 reported measurable rain, showing that the higher elevations did much better. Here at the house we had lots of lightning and thunder, several outflows and a couple of brief spits of rain, amounting to a trace. But the cool outflows and strong smell of rain made for a great evening.
This morning the moisture contents over southern Arizona have continued to increase. The TWC sounding is very moist and indicates the most CAPE present for the season so far. The IPW products and surface observations show that the surge of GoC moisture which began midday on Wednesday has pushed north almost to Las Vegas. IPW at Tucson is 38 mm this morning and Phoenix has 41 mm.
Winds in the upper and lower troposphere are light and variable, but steering level winds from 400 to 600 mb are from the east-northeast at 15 to 30 kts. There are no synoptic features of note today, except for the moderate wind flow around the midlevel anticyclone and perhaps a bit of midlevel cool advection. Expect that it will be another active day across much of southern Arizona. With higher moisture and lower cloud bases, the threat of heavy rain is greater today and the possibility of severe downbursts remains significant. The increased CAPE will allow better propagation of mountain storms into the deserts during the afternoon and evening.
So, another active day likely with lightning fireworks for the Fourth.
Thursday, July 03, 2008
Weather Discussion for Thursday July 3rd 2008
Prepared Thursday July 3rd 8:30 am
Low-level moisture has continued to push into the lower elevations of all of southern Arizona during the night. Moisture increases and southeasterly winds are most spectacular over the lower Colorado River basin as per Yuma surface observations, the KYUX Doppler velocities (See Figure 1 and Figure 2) and the GOES IPW (Figure 3). Winds at 1500 UTC this morning are gusting 20 to 30 kts at Yuma and the dewpoint has risen into the lower 70s. The VAD shown in Figure 2 indicates that the surge of GoC air may bextend up to 4,000 ft AGL.
The Tucson 1200 UTC sounding this morning shows a slight increase of low-level moisture and is a bit dry relative to GPS IPW. There is a very deep residual boundary layer from yesterday and some CAPE indicated over low elevations, with CAPE over the higher mountains likely to be quite substantial. This afternoon's CAPE at lower elevations will be determined by how the low level moisture is advected by low-level winds, any further increase in moisture, and also by any warming that might occur between 500 and 400 mb - so estimating desert CAPE is toughest aspect of this afternoon's forecast.
Steering winds are likely to be northeast to east at 20 to 25 kts around 0000 UTC, while upper-level winds will blow the anvils off to the southeast - an excellent shear configuration for severe thunderstorms in southeastern Arizona. With diurnal afternoon low-level winds from the west-northwest, the shear profile below 500 mb will be supportive of strong, mesoscale outflows.
The threat for severe macroburst winds today is high, and depending on how the CAPE evolves there may also be some heavy rains in lower elevations and possibly hail. Hail is quite likely in higher elevations.
All-in-all looks like a good setup for a significant thunderstorm day here in southeast Arizona and also in much of the Southwest. As is often the case here in southeast Arizona, the outlook for tomorrow will be strongly impacted by how convection evolves late today and tonight - the NAM indicates even more activity tomorrow but this could be impacted by strong outflows later today and tonight. An interesting 4th regardless.
Low-level moisture has continued to push into the lower elevations of all of southern Arizona during the night. Moisture increases and southeasterly winds are most spectacular over the lower Colorado River basin as per Yuma surface observations, the KYUX Doppler velocities (See Figure 1 and Figure 2) and the GOES IPW (Figure 3). Winds at 1500 UTC this morning are gusting 20 to 30 kts at Yuma and the dewpoint has risen into the lower 70s. The VAD shown in Figure 2 indicates that the surge of GoC air may bextend up to 4,000 ft AGL.
The Tucson 1200 UTC sounding this morning shows a slight increase of low-level moisture and is a bit dry relative to GPS IPW. There is a very deep residual boundary layer from yesterday and some CAPE indicated over low elevations, with CAPE over the higher mountains likely to be quite substantial. This afternoon's CAPE at lower elevations will be determined by how the low level moisture is advected by low-level winds, any further increase in moisture, and also by any warming that might occur between 500 and 400 mb - so estimating desert CAPE is toughest aspect of this afternoon's forecast.
Steering winds are likely to be northeast to east at 20 to 25 kts around 0000 UTC, while upper-level winds will blow the anvils off to the southeast - an excellent shear configuration for severe thunderstorms in southeastern Arizona. With diurnal afternoon low-level winds from the west-northwest, the shear profile below 500 mb will be supportive of strong, mesoscale outflows.
The threat for severe macroburst winds today is high, and depending on how the CAPE evolves there may also be some heavy rains in lower elevations and possibly hail. Hail is quite likely in higher elevations.
All-in-all looks like a good setup for a significant thunderstorm day here in southeast Arizona and also in much of the Southwest. As is often the case here in southeast Arizona, the outlook for tomorrow will be strongly impacted by how convection evolves late today and tonight - the NAM indicates even more activity tomorrow but this could be impacted by strong outflows later today and tonight. An interesting 4th regardless.
Sunday, June 29, 2008
Weather Discussion - 9:00 am Sunday June 29, 2008
There are many interesting things happening over the Southwest and so this discussion.
For the past week or so there have been daily thunderstorms over southeast, and sometimes central, Arizona. Moisture values and CAPE have generally remained marginal with IPW values of around 25 mm. Thursday afternoon (the 26th) IPW increased briefly above 30 mm and there was ample CAPE over lower elevations of southeast Arizona for severe storms and heavy rains to occur in the Tucson metro area. The street flooding here on the north side of town was quite impressive, even though at the house there was only 0.33" of rainfall. Temperatures in middle levels have remained quite cool through this period, with temps at 500 mb of -8 to -10 C, and thus there has been CAPE around even though moisture values were low.
On Thursday the high, subtropical values of IPW (>37.5 mm) had inched northward toward the end of the GoC and the borderlands. This morning the subtropical moisture has retreated southward and covers only about the southern third of the GoC.
This morning the Tucson sounding indicates that there will probably be CAPE present this afternoon at lower elevations in southeastern AZ. If we end up with 4 g/kg in the well-mixed boundary layer (BL) there will be slight CAPE, but it looks like the value could be 5 g/kg or even greater. Steering-level winds are easterly at about 20kt. There is a weak upper-level SW over New Mexico and the NAM forecasts part of this feature to move southwestward and interact with the northern end of a quite pronounced tropical wave. So the potential for storms appears enhanced today, especially given that 500 mb temperatures remain in the -8 to -10 C range across all of the southwest. There is also pronounced westward advection of higher moisture values across southern New Mexico. By afternoon there should be substantial moisture convergence over southeastern Arizona as the afternoon diurnal northwesterly winds butt into the easterly flow from New Mexico. Thus, there appears to be high potential for a significant storm day over southeastern AZ today, with severe macrobursts likely - given the high cloud bases and very hot subcloud BL.
In the longer term it finally appears that a wave of significance will move across the lower GoC. The models indicate substantial cool advection at 700 mb with the tropical wave that is now over Mexico and indicate significant storm activity likely in Sinaloa and southern Sonora - perhaps even moving out over the GoC. It would be nice to have some sounding observations over Mexico to help one evaluate the model forecasts, but all of northern Mexico has been without upper-air data for almost a month now. The evolution and movement of the wave, as predicted by the models, as well as the cool advection and rainfall would trigger a low-level surge of high moisture values into southern Arizona sometime between early morning on Tuesday and mid-day on Wednesday.
All in all, it looks like a number of very interesting days are on tap for us here in southeastern Arizona.
For the past week or so there have been daily thunderstorms over southeast, and sometimes central, Arizona. Moisture values and CAPE have generally remained marginal with IPW values of around 25 mm. Thursday afternoon (the 26th) IPW increased briefly above 30 mm and there was ample CAPE over lower elevations of southeast Arizona for severe storms and heavy rains to occur in the Tucson metro area. The street flooding here on the north side of town was quite impressive, even though at the house there was only 0.33" of rainfall. Temperatures in middle levels have remained quite cool through this period, with temps at 500 mb of -8 to -10 C, and thus there has been CAPE around even though moisture values were low.
On Thursday the high, subtropical values of IPW (>37.5 mm) had inched northward toward the end of the GoC and the borderlands. This morning the subtropical moisture has retreated southward and covers only about the southern third of the GoC.
This morning the Tucson sounding indicates that there will probably be CAPE present this afternoon at lower elevations in southeastern AZ. If we end up with 4 g/kg in the well-mixed boundary layer (BL) there will be slight CAPE, but it looks like the value could be 5 g/kg or even greater. Steering-level winds are easterly at about 20kt. There is a weak upper-level SW over New Mexico and the NAM forecasts part of this feature to move southwestward and interact with the northern end of a quite pronounced tropical wave. So the potential for storms appears enhanced today, especially given that 500 mb temperatures remain in the -8 to -10 C range across all of the southwest. There is also pronounced westward advection of higher moisture values across southern New Mexico. By afternoon there should be substantial moisture convergence over southeastern Arizona as the afternoon diurnal northwesterly winds butt into the easterly flow from New Mexico. Thus, there appears to be high potential for a significant storm day over southeastern AZ today, with severe macrobursts likely - given the high cloud bases and very hot subcloud BL.
In the longer term it finally appears that a wave of significance will move across the lower GoC. The models indicate substantial cool advection at 700 mb with the tropical wave that is now over Mexico and indicate significant storm activity likely in Sinaloa and southern Sonora - perhaps even moving out over the GoC. It would be nice to have some sounding observations over Mexico to help one evaluate the model forecasts, but all of northern Mexico has been without upper-air data for almost a month now. The evolution and movement of the wave, as predicted by the models, as well as the cool advection and rainfall would trigger a low-level surge of high moisture values into southern Arizona sometime between early morning on Tuesday and mid-day on Wednesday.
All in all, it looks like a number of very interesting days are on tap for us here in southeastern Arizona.
Monday, June 23, 2008
II. Problems With the TWC Soundings on 23 June 2008
Problems with the data from the RRS sondes are again starting to impact the analysis of the soundings taken at TWC and the forecasting of convection here in southeastern Arizona.
The FSL time series comparison of GPS IPW versus TWC IPW since the 19th of June indicates that 5 soundings were apparently too dry, while one sounding (1200 UTC 19 June) was very wet relative to GPS IPW. See Figure 1. Careful monitoring of the remotely sensed IPW continues to be the best way to make an initial assessment of how accurate a given TWC sounding might be.
The 00Z sounding last evening (see Figure 2) indicated a deep, well-mixed boundary layer extending up to 500 mb; however, the moisture structure was quite questionable, with very dry conditions off the surface and no recovery to a well-mixed value. This led to the "dry" sounding wrt IPW.
The 12Z sounding this morning (see Figure 3) indicates a very deep residual boundary layer, but the moisture structure is extremely erratic. The IPW values correspond well. Given the unrealistic physical nature of the Td data, I suspect that the agreement of the two IPW values is essentially a coincidence this morning. If the afternoon BL mixes toward 5 g/kg, then there is a small amount of CAPE present; however, if it mixes toward 4 g/kg then there is no CAPE present. Given the erratic Td data trace it is very hard to make a subjective forecast of the late afternoon sounding.
The FSL time series comparison of GPS IPW versus TWC IPW since the 19th of June indicates that 5 soundings were apparently too dry, while one sounding (1200 UTC 19 June) was very wet relative to GPS IPW. See Figure 1. Careful monitoring of the remotely sensed IPW continues to be the best way to make an initial assessment of how accurate a given TWC sounding might be.
The 00Z sounding last evening (see Figure 2) indicated a deep, well-mixed boundary layer extending up to 500 mb; however, the moisture structure was quite questionable, with very dry conditions off the surface and no recovery to a well-mixed value. This led to the "dry" sounding wrt IPW.
The 12Z sounding this morning (see Figure 3) indicates a very deep residual boundary layer, but the moisture structure is extremely erratic. The IPW values correspond well. Given the unrealistic physical nature of the Td data, I suspect that the agreement of the two IPW values is essentially a coincidence this morning. If the afternoon BL mixes toward 5 g/kg, then there is a small amount of CAPE present; however, if it mixes toward 4 g/kg then there is no CAPE present. Given the erratic Td data trace it is very hard to make a subjective forecast of the late afternoon sounding.
The Haboob of Saturday Evening June 21st 2008
This was probably the first significant event, for southeast Arizona, of the 2008 summer thunderstorm season. Widespread convection occurred over parts of southeast Arizona and particularly over southwest New Mexico and northern Mexico. See Figure 1.
High cloud bases and a very hot boundary layer led to an organized, mesoscale outflow that affected much of southeastern Arizona. Passage here in Tucson occurred about 4:30 pm local time. The outflow was well-depicted as a fine line on the KEMX reflectivity display see Figure 2.
Note that Douglas, Arizona, reported a severe convective gust of 51 kt at 3:32 pm local time after the haboob had moved passed. This severe storm event did not make it into SPC's list of wind events for the 21st.
We were returning to Tucson from Chicago and landed about 10:00 pm local time. The approach was very bumpy and winds were still gusty from the east to southeast. The air was heavily laden with dust, giving the 3/4 moon a very strange and dirty yellow-brown appearance.
Thursday, June 12, 2008
REST OF MONTH LOOKS INTERESTING FOR SOUTHWEST
Both GFS and NAM model forecasts continue to be quite interesting for the Southwest.
Appears that there may be high-based, dry lightning storms over the mountains of far southeast AZ this weekend. Definitely not good, given the extreme dry conditions of last two and a half months. Only 0.09" of rain here at house since March 17th!
In the longer term, the GFS ensemble members keep a strong, middle-level anticyclone north Mexico/southern Plains, and then tend to shift it northward during last 10 days of month. Throw a tropical disturbance into this pattern and who knows what we might see down here.
I'm off to Wisconsin where it will be green and wet and probably muddy.
Appears that there may be high-based, dry lightning storms over the mountains of far southeast AZ this weekend. Definitely not good, given the extreme dry conditions of last two and a half months. Only 0.09" of rain here at house since March 17th!
In the longer term, the GFS ensemble members keep a strong, middle-level anticyclone north Mexico/southern Plains, and then tend to shift it northward during last 10 days of month. Throw a tropical disturbance into this pattern and who knows what we might see down here.
I'm off to Wisconsin where it will be green and wet and probably muddy.
Friday, June 06, 2008
OVERVIEW of RRS SOUNDINGS 6 JUNE 2008
I have been involved in other things last few days. Have just taken a look at today's soundings and report the following:
0000 UTC soundings with superadiabatic layers aloft apparently due to wetbulbing:
UIL SLE BOI OTX FWD OAX SHV MSP TLH BMX APX MFL
ABR has an extreme super layer aloft but it is not due to wetbulbing. LBF flight missing.
12000 UTC soundings with superadiabatic layers aloft apparently due to wetbulbing:
UIL SLE ILX OTX DVN SGF
OUN sounding appears very strange for unknown reasons.
0000 UTC soundings with superadiabatic layers aloft apparently due to wetbulbing:
UIL SLE BOI OTX FWD OAX SHV MSP TLH BMX APX MFL
ABR has an extreme super layer aloft but it is not due to wetbulbing. LBF flight missing.
12000 UTC soundings with superadiabatic layers aloft apparently due to wetbulbing:
UIL SLE ILX OTX DVN SGF
OUN sounding appears very strange for unknown reasons.
Friday, May 23, 2008
SUSPECT RRS DATA FOR 23 MAY 2008
Numerous data problems continue in the RRS soundings.
Overview of suspect data for 0000 UTC 23 May 2008:
Superadiabatic layer(s) aloft:
LBF UNR SLE TWC FWD LIX TLH LCH MFL BUF
Additionally - the LBF flight was incomplete; the MHX flight was missing all winds except that at the surface; the LIX flight also exhibited a warm spike and extremely noisey data; the JAN flight was terminated.
Overview of suspect data for 1200 UTC 23 May 2008:
Superadiabatic layer(s) aloft:
LBF UNR TWC FWD OUN TLH MHX DVN BMX BNA APX RNK
Additionally - the UNR and MFL flights exhibited extreme noise in the RH data and the bizarre TLH flight was terminated.
Overview of suspect data for 0000 UTC 23 May 2008:
Superadiabatic layer(s) aloft:
LBF UNR SLE TWC FWD LIX TLH LCH MFL BUF
Additionally - the LBF flight was incomplete; the MHX flight was missing all winds except that at the surface; the LIX flight also exhibited a warm spike and extremely noisey data; the JAN flight was terminated.
Overview of suspect data for 1200 UTC 23 May 2008:
Superadiabatic layer(s) aloft:
LBF UNR TWC FWD OUN TLH MHX DVN BMX BNA APX RNK
Additionally - the UNR and MFL flights exhibited extreme noise in the RH data and the bizarre TLH flight was terminated.
Thursday, May 22, 2008
MANY SUSPECT SOUNDINGS THIS MORNING
While there were lots of bad or suspect soundings last evening, this morning's data appear quite bad. At least for the number of flights with obviously suspect layers. I guess this reflects the important weather systems affecting the continental US today - Thursday 22 May 2008.
Visually obvious problems appear in the sounding data as per:
Warm spikes at GGW RIW
Superadiabatic layers aloft at GJT GGW(3) SHV TOP OMA AMA JAN TLH MFL(2)
Suspect layer (Opposite of wet bulb superadiabatic) at UIL SLE MFR APX
Some of these are quite amazing. The sounding data can be easily viewed at Univ. of WY's upper air page:
http://weather.uwyo.edu/upperair/sounding.html
Note that two of the suspect soundings are from non RRS stations - TOP which flew into an MCS and MFR which showed a weak Op-Super layer from its VIZ instrument.
I call the strange layers "Op-Super" that occur when sonde exits cloud into drier and warmer air and T increases rapidly but RH stays at 100% for a while. This likely indicates a hygrister problem vs wet bulbing under same conditions which indicates a wetted thermister.
Visually obvious problems appear in the sounding data as per:
Warm spikes at GGW RIW
Superadiabatic layers aloft at GJT GGW(3) SHV TOP OMA AMA JAN TLH MFL(2)
Suspect layer (Opposite of wet bulb superadiabatic) at UIL SLE MFR APX
Some of these are quite amazing. The sounding data can be easily viewed at Univ. of WY's upper air page:
http://weather.uwyo.edu/upperair/sounding.html
Note that two of the suspect soundings are from non RRS stations - TOP which flew into an MCS and MFR which showed a weak Op-Super layer from its VIZ instrument.
I call the strange layers "Op-Super" that occur when sonde exits cloud into drier and warmer air and T increases rapidly but RH stays at 100% for a while. This likely indicates a hygrister problem vs wet bulbing under same conditions which indicates a wetted thermister.
Friday, May 16, 2008
A Quick Look at This Morning's 1200 UTC Soundngs
Friday Morning 16 May 2008
I have had time to take a quick pass through the morning soundings.
Soundings having a super-adiabatic layer aloft include:
MAF BRO LIX TLH MHX GYX
Soundings having a warm spike aloft between 0 and -10C include:
GJT LIX IAD
Too busy today to take a careful look at any of these.
I have had time to take a quick pass through the morning soundings.
Soundings having a super-adiabatic layer aloft include:
MAF BRO LIX TLH MHX GYX
Soundings having a warm spike aloft between 0 and -10C include:
GJT LIX IAD
Too busy today to take a careful look at any of these.
Thursday, May 15, 2008
Super-adiabatic Layers This Morning
The following soundings exhibit elevated super-adiabatic layers this morning for the 1200 UTC flights:
AMA FWD BNA LBF LZK JAN LCH
The problem at LBF was due to an intense warm spike.
The too cool layers in several of these soundings cause computed CAPE to be inaccurate.
I cross-checked the NCAR RAP plots with those at Wyoming this morning, and all the above
problem soundings were similar at each web page.
LCH is the most bizarre sounding of the bunch. The instrument apparently was launched into
a thunderstorm or deep convection.
AMA FWD BNA LBF LZK JAN LCH
The problem at LBF was due to an intense warm spike.
The too cool layers in several of these soundings cause computed CAPE to be inaccurate.
I cross-checked the NCAR RAP plots with those at Wyoming this morning, and all the above
problem soundings were similar at each web page.
LCH is the most bizarre sounding of the bunch. The instrument apparently was launched into
a thunderstorm or deep convection.
RE Flagstaff Sounding Previous Post
The bad sounding shown for Flagstaff was apparently due to the following:
Data were missing for for a short period.
Operator interpolated data for the missing period.
A saturated point was interpolated with T/Td spread shown as //
The NCAR Rap sounding decoder did not interpret the // correctly,
producing the very strange sounding on their web page.
The decoders at Wyoming and SPC plotted the data correctly.
Data were missing for for a short period.
Operator interpolated data for the missing period.
A saturated point was interpolated with T/Td spread shown as //
The NCAR Rap sounding decoder did not interpret the // correctly,
producing the very strange sounding on their web page.
The decoders at Wyoming and SPC plotted the data correctly.
Wednesday, May 14, 2008
Suspect Soundings - Two Recent Examples
The figures below show soundings from Flagstaff AZ yesterday morning at 1200 UTC and from Ft. Worth TX this morning at 1200 UTC. Both have suspect layers, but the cause of the problems are not obvious.
Figure 1 - KFGZ
This sounding indicates a very dry layer of almost 100 mb vertical extent just above 700 mb. It had been raining for several hours and at the time of release Flagstaff was reporting moderate to heavy snowfall. The snow continued for several hours after sounding time. The dry layer certainly does not seem physically realistic, given the steady precipitation event that was underway.
Figure 2 - KFWD
This morning's sounding at FWD indicates a strongly super-adiabatic lapse at about 710 mb. This excursion causes a layer that appears to be several degrees too cool from about 710 to 550 mb. The net result is that sounding analysis software routines would produce CAPE values that were likely too great. Since the sonde did not, apparently, rise into a very dry layer, the reason for the super-adiabatic layer aloft is not clear.
Both of these soundings may illustrate random instabilities within these two RSS sonde's internal electronics, but this is just a guess on my part.
Figure 1 - KFGZ
This sounding indicates a very dry layer of almost 100 mb vertical extent just above 700 mb. It had been raining for several hours and at the time of release Flagstaff was reporting moderate to heavy snowfall. The snow continued for several hours after sounding time. The dry layer certainly does not seem physically realistic, given the steady precipitation event that was underway.
Figure 2 - KFWD
This morning's sounding at FWD indicates a strongly super-adiabatic lapse at about 710 mb. This excursion causes a layer that appears to be several degrees too cool from about 710 to 550 mb. The net result is that sounding analysis software routines would produce CAPE values that were likely too great. Since the sonde did not, apparently, rise into a very dry layer, the reason for the super-adiabatic layer aloft is not clear.
Both of these soundings may illustrate random instabilities within these two RSS sonde's internal electronics, but this is just a guess on my part.
Thursday, May 08, 2008
Problem Soundings 0000 UTC May 9th
My quick look at the soundings last evening identified two RSS flights that exhibited strongly super-adiabatic lapse rates in shallow layers aloft. These soundings were taken at Birmingham, AL, and Sterling, VA.
Note that the RRS operational procedures indicate that layers such as these should be removed via manual editing by the operator, and provide instructions for how this should be done.
Figure 1 (00Z BMX)
The layer of interest here extends from about 630 mb to 610 mb. The sonde apparently had moisture on the thermistor, and perhaps on the hygristor. When the instrument exited a deep, cloudy layer it encountered very dry air aloft and evaporative cooling of the sensors probably produced the super-adiabatic layer.
Figure 2 (00Z IAD)
The layer of interest here is only about 10 mb deep and is located near 740 mb. The reason for this super-adiabatic layer is not obvious, since the entir atmosphere appears to be quite moist. The sounding apparently did not exit cloud into a very dry layer above. It is possible that the instrument was in a saturated updraft and exited the updraft suddenly. It is also possible that the hygristor did not respond adequately to a layer that was considerably drier than the data indicate.
During the next few months I'll be paying particular interest in identifying soundings in which bad data have complicated the diagnosis of CAPE or potentially caused forecasting difficulties.
If readers note soundings that seem to be candidates, as per above, for closer examination, please feel free to alert me to them. Thanks, Bob bob@squidinkbooks.com
Wednesday, May 07, 2008
BLOG will be active now for the spring/summer
I am beginning again to monitor the RRS Sippican sounding data, as I start preparing a formal paper. This paper will document the often poor, and physically bizarre, soundings produced by the Sippican radiosondes the NWS has switched to at most sites in the US.
Today's winning example of a strange sounding is that taken at Ft. Worth TX at 1200 UTC.
http://www.rap.ucar.edu/weather/upper/fwd.gif
Today's winning example of a strange sounding is that taken at Ft. Worth TX at 1200 UTC.
http://www.rap.ucar.edu/weather/upper/fwd.gif
Monday, March 17, 2008
Cold Cutoff in the Southwest
Yet another success for the long-range models, especially theECMWF, which correctly forecast the development of the cold, midlevel low currently over the Southwest - beginning from about 5 to 6 days out.
The system produced more precipitation than I was expecting, given the very low precipitable water values. Here at the house, I measured 0.29" through 7 am this morning and light showers remain in the area. Low this morning was 33F.
Precipitation yesterday was from convective showers in the cold, unstable air. I did not hear any thunder here at the house. During midafternoon northern and western parts of the Tucson metro area had heavy showers of graupel (AKA snow pellets) and the ground was covered in some spots.
Perhaps some more of this today, before the system moves on east. It's hard to know how unstable it is this morning, since the somewhat critical Tucson upper-air sounding was missing both last evening and again this morning.
The NWS forecast this morning (see below) mentions the possibility of showers, thunder, and sleet. While showers accompanied by graupel may occur, the liklihood of sleet is extremely small, today or with any winter weather event in the Tucson metro area, since sleet results when raindrops fall through a layer of subfreezing air at or very near the surface. Definitions of graupel and sleet are also below.
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Today: A chance of rain showers possibly mixed with sleet, mainly after 11am. Some thunder is also possible. Partly sunny, with a high near 53. South southeast wind 9 to 14 mph becoming west northwest. Chance of precipitation is 30%. Little or no snow accumulation expected.
From the Glossary of Meteorology:
snow pellets (Also called soft hail, graupel, tapioca snow.) Precipitation consisting of white, opaque, approximately round (sometimes conical) ice particles having a snowlike structure, and about 2-5 mm in diameter. Snow pellets are crisp and easily crushed, differing in this respect from snow grains. They rebound when they fall on a hard surface and often break up. In most cases, snow pellets fall in shower form...
sleet or grains of ice, generally transparent, globular, solid grains of ice that have formed from the freezing of raindrops or the refreezing of largely melted snowflakes when falling through a below-freezing layer of air near the earth's surface....
The system produced more precipitation than I was expecting, given the very low precipitable water values. Here at the house, I measured 0.29" through 7 am this morning and light showers remain in the area. Low this morning was 33F.
Precipitation yesterday was from convective showers in the cold, unstable air. I did not hear any thunder here at the house. During midafternoon northern and western parts of the Tucson metro area had heavy showers of graupel (AKA snow pellets) and the ground was covered in some spots.
Perhaps some more of this today, before the system moves on east. It's hard to know how unstable it is this morning, since the somewhat critical Tucson upper-air sounding was missing both last evening and again this morning.
The NWS forecast this morning (see below) mentions the possibility of showers, thunder, and sleet. While showers accompanied by graupel may occur, the liklihood of sleet is extremely small, today or with any winter weather event in the Tucson metro area, since sleet results when raindrops fall through a layer of subfreezing air at or very near the surface. Definitions of graupel and sleet are also below.
-------------------------------------------------------------------
Today: A chance of rain showers possibly mixed with sleet, mainly after 11am. Some thunder is also possible. Partly sunny, with a high near 53. South southeast wind 9 to 14 mph becoming west northwest. Chance of precipitation is 30%. Little or no snow accumulation expected.
From the Glossary of Meteorology:
snow pellets (Also called soft hail, graupel, tapioca snow.) Precipitation consisting of white, opaque, approximately round (sometimes conical) ice particles having a snowlike structure, and about 2-5 mm in diameter. Snow pellets are crisp and easily crushed, differing in this respect from snow grains. They rebound when they fall on a hard surface and often break up. In most cases, snow pellets fall in shower form...
sleet or grains of ice, generally transparent, globular, solid grains of ice that have formed from the freezing of raindrops or the refreezing of largely melted snowflakes when falling through a below-freezing layer of air near the earth's surface....
Wednesday, March 12, 2008
DEVELOPING WEATHER EVENT
Finally looks like we may have some clouds and weather here in SE AZ during the weekend.
The ECMWF and the GFS ensemble members are all pretty much in agreement now, indicating a strong wave digging down the west coast, with the eventual cutoff affecting us from about 96 to 144 hours - from 00 UTC model runs last evening.
There are about 5 waves strung out across the northern Pacific and it's not clear which one kicks up the ridge into AK, forcing the wave down the coast. Obviously all the models have keyed on one of these to be the agent of change.
The models appear to predict about a quarter to half an inch of precip at lower elevations by late Monday afternoon. Uncertainties this far out - how long will the wave affect SE AZ - some model runs keep it more isolated from the main flow to the north; how much moisture will the system pickup (the ECMWF hints at better moisture flowing northward toward the end of the event, while - surprise - the GFS members stay drier). Only 10 of 12 GFS ensemble members predict measurable rainfall at lower elevations in SE AZ during the event.
Current fcst POPs for both TUS metro and also top of Catalinas max out at 30% for Sunday night. PHX has issued a hazardous weather outlook for this event already (see the nice early am FD from PHX). Will be interesting to watch how this event evolves.
Different topic - My total precip for Dec/Jan/Feb here at house was 5.84 inches -not bad for a la nina winter! Actually not bad for any of past ten winters - beaten only (I think) by the 97-98 el nino winter.
The ECMWF and the GFS ensemble members are all pretty much in agreement now, indicating a strong wave digging down the west coast, with the eventual cutoff affecting us from about 96 to 144 hours - from 00 UTC model runs last evening.
There are about 5 waves strung out across the northern Pacific and it's not clear which one kicks up the ridge into AK, forcing the wave down the coast. Obviously all the models have keyed on one of these to be the agent of change.
The models appear to predict about a quarter to half an inch of precip at lower elevations by late Monday afternoon. Uncertainties this far out - how long will the wave affect SE AZ - some model runs keep it more isolated from the main flow to the north; how much moisture will the system pickup (the ECMWF hints at better moisture flowing northward toward the end of the event, while - surprise - the GFS members stay drier). Only 10 of 12 GFS ensemble members predict measurable rainfall at lower elevations in SE AZ during the event.
Current fcst POPs for both TUS metro and also top of Catalinas max out at 30% for Sunday night. PHX has issued a hazardous weather outlook for this event already (see the nice early am FD from PHX). Will be interesting to watch how this event evolves.
Different topic - My total precip for Dec/Jan/Feb here at house was 5.84 inches -not bad for a la nina winter! Actually not bad for any of past ten winters - beaten only (I think) by the 97-98 el nino winter.
Thursday, January 31, 2008
BRIEF SUMMARY OF JANUARY 2008
The weather for the winter continued fairly wet and cold here at the house during January 2008.
There was measurable rainfall on only 4 days but the total, mostly from the storms of the 7th and of the 27th/28th, was 1.00 inch. The storm late in the month produced much flooding and runoff after very heavy rains at higher elevations. The Rillito wash is still running today.
After a very cold December (our gas bill for heating in December was the highest ever during our ten years in the house), January was also fairly cold. There were 18 mornings with low temperatures of 32F or colder. Half of these days had lows of 27F or colder.
The coldest mornings occurred on the 18th - 20th with readings of 20F, 20F, and 21F. This morning, the 31st, was also cold with a low of 22F. There was a period of 14 consecutive days from the 10th through the 23rd with lows of 32F or colder.
So, probably another big gas bill.
Appears that February will also start out unsettled with perhaps more rain during this strange la nina winter.
There was measurable rainfall on only 4 days but the total, mostly from the storms of the 7th and of the 27th/28th, was 1.00 inch. The storm late in the month produced much flooding and runoff after very heavy rains at higher elevations. The Rillito wash is still running today.
After a very cold December (our gas bill for heating in December was the highest ever during our ten years in the house), January was also fairly cold. There were 18 mornings with low temperatures of 32F or colder. Half of these days had lows of 27F or colder.
The coldest mornings occurred on the 18th - 20th with readings of 20F, 20F, and 21F. This morning, the 31st, was also cold with a low of 22F. There was a period of 14 consecutive days from the 10th through the 23rd with lows of 32F or colder.
So, probably another big gas bill.
Appears that February will also start out unsettled with perhaps more rain during this strange la nina winter.
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