November 2014: Nice Seanonal Thanksgiving Ahead

[srainhoutx]

Afternoon Briefing from Jeff:

Cold mid November day across the area even with full sun and this will transition into a freezing night.

Freeze warning in effect for those areas that did not freeze last Friday (mainly along and south of I-10 and much of Harris County). Cold arctic high continues to build into the region this afternoon with gusty winds and highs temperatures barely making it to 50 degrees under cold air advection. Dewpoints have tumbled into the upper 10’s and 20’s over the region and once the sun sets the temperatures will begin to fall quickly as wind die down. GFS is showing 27 for IAH and Victoria tonight, 24 for College Station, and 22 for Conroe with several hours below freezing expected. Urban heat core may keep areas inside the Beltway in the 29-31 degree range, but still a light freeze. Northern counties will be borderline for a hard freeze warning or below 25 for more than 2 hours.

Protections for a widespread freeze should be taken including protecting of sensitive vegetation and citrus and pets and livestock. Most pipes will be ok at the forecasted temperatures, but any exposed outside pipes and faucet connectors should be protected to reduce the risk of freezing.

Warm up begins late Tuesday as high pressure moves eastward allowing winds to become ESE and SE by Wednesday. Fairly quick moisture return is likely with clouds and rain back in the forecast by Thursday and likely lasting through the weekend. Unlike this past weekend, sustained southerly flow will result in a wet warm and humid instead of cold. The incoming Saturday system is looking fairly healthy on the model guidance and will need to be watched for any potential severe and heavy rainfall threat.

[dljones33]

46 here in Bear Creek area but I don't believe it. Luckily we only have 2 plants that have to be brought inside, the rest will just have to fend for themselves and be cut back to the ground come Spring. If you are a plant at my house and can't survive in Houston weather then well, you just have to go. Trouble is, we have a lot of plants that make it and the deadwood is a pain the cut off and trash. On the flip side, mosquito control comes to mind!

[jasons2k]

Everything here is covered and ready, except the last Majesty palm. I also dumped the rain gauge - it had .55" in it from the pre-frontal rains. Hardly the widespread 1-3" we were expecting. Did anyone even get an inch from this?

[Katdaddy]

A fast moving cirrus shield has led to slightly warmer overnight temps with many areas in SE TX remaining at 31-32F and a few mid to upper 30s. Near the coast Galveston remains in the low 40s. The cirrus shield will likely create a beautiful sunrise. Mid 50s today as the warming trend begins. Highs in the mid 70s across SE TX by the end of the week however this will also bring increasing rain and thunderstorm chances. Models continue to indicate a possible severe weather event beginning Saturday across Central and SE TX pushing into the Lower MS Valley. The SPC has Central and SE TX highlighted with at least a 30% chance of severe storms Saturday.

[TexasBreeze]

It reached 32 at IAH in between obs. Official for wxman57 and his contest!:)

[srainhoutx]

Impressive storm signal shaping up across our Region this weekend.

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CST TUE NOV 18 2014

VALID 211200Z - 261200Z

...DISCUSSION...
A PROGRESSIVE FLOW REGIME WILL CHARACTERIZE THE UPPER PATTERN OVER
THE U.S. DAY 4 INTO DAY 5...BEFORE A RETURN TO A BLOCKING PATTERN
WITH AMPLIFICATION OF A LARGE-SCALE TROUGH DAYS 6-8.

DAYS 4-5...PARTIALLY MODIFIED GULF MOISTURE WILL ADVECT NWD THROUGH
CNTRL/ERN TX IN ADVANCE OF A SRN STREAM SHORTWAVE TROUGH THAT IS
FORECAST TO REACH THE SRN PLAINS EARLY DAY 5 AND CONTINUE THROUGH TX
INTO THE LOWER MS VALLEY REGION. MODEST AMPLITUDE AND TIMING
DIFFERENCES EXISTS AMONG ENSEMBLE MEMBERS. ALSO THE NAM IS SLIGHTLY
FASTER AND LESS AMPLIFIED THAN THE ECMWF AND GFS WHICH ARE BOTH
SIMILAR AND HAVE SHOWN RUN TO RUN CONSISTENCY. GENERAL PATTERN WOULD
SUGGEST A THREAT FOR SEVERE STORMS MAY DEVELOP OVER PORTIONS OF
CNTRL TX EARLY SATURDAY AND SERN TX INTO THE LOWER MS VALLEY LATER
SATURDAY INTO SATURDAY NIGHT. STORMS WILL LIKELY GROW UPSCALE INTO
AN MCS...BUT TENDENCY MIGHT BE FOR THIS ACTIVITY TO DEVELOP EWD MORE
QUICKLY THAN THE ATMOSPHERE CAN DESTABILIZE SUFFICIENTLY WITH EWD
EXTEND INTO THE LOWER MS VALLEY.

DAY 6...SOME SEVERE THREAT WILL LIKELY PERSIST FROM SRN PARTS OF THE
GULF COASTAL STATES TO THE CAROLINAS. HOWEVER...AT THIS TIME TOO
MUCH UNCERTAINTY EXISTS REGARDING EXTENT TO WHICH ONGOING CONVECTION
WILL LIMIT DESTABILIZATION POTENTIAL.

..DIAL.. 11/18/2014

[srainhoutx]

IAH did reach freezing...IAH had a low of 32 degrees F on 11/18/14. Congrats wxman57 in winning that office pool!

[jasons2k]

Well, I am happy even though I spent about an hour last night getting ready. I hit a low of 33. A bust of 8 degrees (using NWS numbers). That's a pretty big bust.

I technically have not had a freeze yet, and technically the NWS should issue a freeze warning for me the next time a freeze is forecast.

They won't.

[unome]

Hooks Airport registered freezing temps for a short time

if you check the 24-hr minimum temps on MesoWest, it looks like most locations northwest of Spring Cypress, between 45 & 290 hit freezing (map defaults to 24-hr high temp) http://www.wrh.noaa.gov/mesowest/gmap.p ... value=maxT

glad we covered the plants

[jasons2k]

Thanks for that map. Looks like most of the Woodlands area avoided a freeze and was warmer than points further south. NWS take notice - you should issue a freeze warning for Southern Montgomery County the next time it's supposed to freeze.

[unome]

yeah, some hot air around The Woodlands, perhaps from paving paradise & putting up parking lots, a mini heat island ?

their temps on NWS come from Hooks Airport, just like ours do, but we are often in different weather conditions than that airport. I guess they have to use the official weather stations that they have & they are not everywhere, no way of knowing how well the other area weather stations are taken care of or calibrated, etc...

whenever our forecast is close to freezing & we have plants we want to protect, we opt on the side of caution, just use common sense & cover up what I want protected - works for us

[SLM87TX]

Also if you are in valley you will be must colder then in other area. So do not trust one weather station to make a decision.

[BlueJay]

I'm so happy to report the beautiful cirrus shield, as Katdaddy pointed out, not only kept our temperature up to 34F this morning but it was a gorgeous sunrise! A win-win.

I also found it curious that Montgomery County did not get a freeze warning in that Conroe was expected to reach 22F. Oh well, nobody is perfect.

I guess I will leave the plants covered for tonight. Who knows, maybe we will freeze tonight.

[srainhoutx]

The afternoon update from the Climate Prediction Center continues to advertise below normal temperatures with near or below normal precipitation across our Region in the Day 8+ Range.

[jasons2k]

There are a number of reasons for the discrepancies. Topography is a major factor, especially more into Montgomery County as it's not a flat as Harris County and locations closer to the coast. That's one reason why Oak Ridge tends to be a bit warmer during radiational cooling events than surrounding areas - it's on a small ridge. Conversely, the Conroe Airport is in a bowl and cold air drains into it, and it’s usually a cold spot.

As for the freeze warning, they did not include Montgomery County and most spots north of I-10 because according to the NWS they have already had the first freeze of the season. They won’t issue subsequent freeze warnings if you have already experienced a freeze.

That said, I think they are in error here. As I noted earlier, and as the maps clearly show, this freeze occurred in pockets, which is not unusual for radiational freezes. I have not had a freeze yet, so if they go by the book, they should indeed issue a freeze warning next time around. But I guarantee you they won’t. It’s actually happened a few times over the last few years.

I’m not the meteorologist in charge for the HGX office, but if I was, I’d err on the side of caution and continue to issue freeze warnings until there was a consistent freeze recorded across all reporting stations within the county in question. That’s what they do in Florida (Ruskin and Melbourne); they closely follow protocol and take it seriously; the same should apply here.

To be honest, as a gardening enthusiast, this lax attitude towards freeze warnings by our local NWS office is a bit irritating. I expect better of paid professionals working in the public interest.

[TexasBreeze]

This has nothing to do with Texas, but is an interesting tidbit. Some places just off the great lakes Erie and Ontario could see 70+ inches of snowfall with the lake-effect machine cranked up this week. I have family up there in Cleveland, OH! I could not imagine having that much snow!!!

http://forecast.weather.gov/showsigwx.p ... GvVrcnnbqA

[BlueJay]

There are a number of reasons for the discrepancies. Topography is a major factor, especially more into Montgomery County as it's not a flat as Harris County and locations closer to the coast. That's one reason why Oak Ridge tends to be a bit warmer during radiational cooling events than surrounding areas - it's on a small ridge. Conversely, the Conroe Airport is in a bowl and cold air drains into it, and it’s usually a cold spot.

As for the freeze warning, they did not include Montgomery County and most spots north of I-10 because according to the NWS they have already had the first freeze of the season. They won’t issue subsequent freeze warnings if you have already experienced a freeze.

That said, I think they are in error here. As I noted earlier, and as the maps clearly show, this freeze occurred in pockets, which is not unusual for radiational freezes. I have not had a freeze yet, so if they go by the book, they should indeed issue a freeze warning next time around. But I guarantee you they won’t. It’s actually happened a few times over the last few years.

I’m not the meteorologist in charge for the HGX office, but if I was, I’d err on the side of caution and continue to issue freeze warnings until there was a consistent freeze recorded across all reporting stations within the county in question. That’s what they do in Florida (Ruskin and Melbourne); they closely follow protocol and take it seriously; the same should apply here.

To be honest, as a gardening enthusiast, this lax attitude towards freeze warnings by our local NWS office is a bit irritating. I expect better of paid professionals working in the public interest.

This is interesting jasons. I did not know that the freeze warnings were handed out only one to a customer.
I don't understand this.

[srainhoutx]

A very informative evening briefing from Jeff:

First freeze of the winter season recorded at IAH this morning with the temperature falling to 32. Very interesting pattern of low temperatures outlined the urban sprawling across Harris and surrounding counties this morning defining heat corridors from development patterns. I will touch on this more below.

Temperatures have tumbled this evening with excellent radiative conditions in place. IAH fell 13 degrees since the sun has set from 53 to 40. Dewpoints currently in the upper 20’s and low 30’s support another freeze and this is favorable given this is night two after cold frontal passage which tends to be the coldest night. However the axis of the arctic surface high is centered in the Beaumont and Lake Charles area and surface observations show southerly winds across at least the western half of SE TX which suggest the temperature tumble will be halted as warmer air is brought inland from the Gulf of Mexico. With that said, would not be surprised to see temperatures approach freezing around midnight or shortly after along and northeast of US 290 and then rise some toward morning. It is very possible it will be colder at 1000pm tonight than at 600am tomorrow morning.

Sustained warming trend will begin on Wednesday after over a week of well below normal temperatures. In fact the gravity of this cold air outbreak can be noted in the record low recorded at Amarillo this morning of 5 degrees and across the nation with nearly 50% of the country with snow cover (33% is average on Christmas Day). The entire state of OK was covered in snow yesterday morning and Dallas recorded a record snow amount of a trace on Monday morning with many locations over N TX having a dusting of snow. Currently November 2014 is running an astounding 8.0 degrees below average for Houston and is currently ranked as the 9th coldest November on record. While a colder and wetter than normal winter is expected across the southern plains, the current cold air outbreak has little bearing on what the rest of winter may exhibit especially with respect to any sustained severe cold air outbreaks and one should be cautious in drawing any conclusions from the recent cold spell and how the rest of winter may play out.

As the large arctic high moves eastward southerly onshore winds will begin to promote moisture return northward. A coastal surface trough will form off the lower TX coast Wednesday and help sling moisture over the top of the surface cold dome. This will result in an increase in cloud cover and can many times slow air mass modification. Chances for rain return by Thursday as a lead short wave in the developing flow aloft moves across TX and interacts with the developing moisture return. Warm front should move inland on Friday with scattered showers continuing to stream northward off the Gulf. Temperatures will warm into the 70’s south of the warm front and dewpoints will rise into the low to mid 60’s. While normally November is not a big sea fog month along the upper TX coast, the recent cold has chilled the bay and nearshore waters into the 50’s. With dewpoints rising into the 60’s or above that of the water temperatures, sea fog will be possible Friday afternoon into Saturday.

Saturday:
Strongly dynamic storm system suggested by model guidance for this Saturday with potential threats for both severe weather and heavy rainfall. Powerful short wave will dive into the southern jet and eject rapidly out of New Mexico into TX on Saturday while the system takes on a slight negative tilt or from SE to NW which suggest little to no SW flow in the mid levels to cap off the air mass. Mid level temperatures look very cool with the storm system which will help promote an unstable air mass only with surface temperatures in the 70’s. Low level shear values look favorable for updraft rotation. Main severe limiting factor at the moment looks to be instability (CAPE of 500-1000 J/kg) across the area. SPC has already highlighted all of SE TX for a severe risk on Saturday with damaging winds and tornadoes likely being the main threats. The far southward placement of the core dynamics with this system suggest a threat is justified. It should be noted that October and November are our secondary severe weather season in SE TX and one of our worst tornado outbreaks ever recorded happened on November 21, 1992 when 4 large supercell thunderstorms produced 6 long tracked tornadoes across Harris County including a devastating ¾ of a mile wide F4 tornado in Channelview. The rest of the week focus will be on the Saturday system and its potential impacts.

The Urban Heat Core:
It has been known for a long time that urban sprawl can alter temperature and weather patterns on local scales. This was first studied in Atlanta in the 1990’s when it was noticed that unusually heavy rainfall was occurring in the late night hours during the summer months. Houston has been no exception to urban development especially on its west and northern flanks in the last few decades and is very clearly noted on clear and cold nights such as last night. Technology and the plethora of temperature data now available between official reporting sites gives a glimpse into just how widely varying the temperatures extremes can be over just a few miles. Low temperature data last night showed very interesting patterns of significantly warmer temperatures along I-10W, US 59S, I-45N, and along HWY 6 between US 290 and I-10. Temperatures along these “urban corridors” ranged anywhere from 3-8 degrees warmer than temperatures only a few miles away. What was striking is how closely the temperature patterns mirrored the major freeways and how “warm” western Harris County temperatures were especially in the Hwy 6 corridor. These observations are far from scientific as the various sensors being reported from home temperature gages are surely not all uniform nor likely all installed equally. Additionally, many of these sensors are likely within subdivisions which already create a warmer background temperature effect so the data set is not easily ready for direct comparison. Another consideration last night was the high clouds which crossed the area and what affect that may have had on the low temperature patterns. A better case could probably be made for tonight if winds were not shifting to the south late.

What can be drawn from the data is that urbanization is certainly resulting in warmer temperature readings especially under strong raditional cooling conditions. It is also noted that significant temperature differences over a very short distance are almost certainly creating microscale surface temperature boundaries during the warmer season which could help foster thunderstorm development. These boundaries are likely on the order of a few miles long and maybe less than 1/4th of a mile wide which cannot be detected on Doppler radar nor high resolution model guidance, but given the temperature discontinuity noted in the data on a clear cold night suggest a similar pattern is likely present on a hot summer day. It is likely that the climate record at BUSH IAH is starting to be skewed due to urban development surrounding the airport with Hooks (Tomball) likely a more representative station for the remaining rural areas of Harris County. The urban heat core has loosely been defined as the area within the 610 loop, but it is clear that development has been sustained enough to likely expand that area to include areas inside Beltway 8 and also to include areas near/along the major freeway systems. It is almost certain that construction of the Grand Parkway system and its resultant urban development along that system will expand the urban heat core outward to the far outer reaches of Harris County over the next decade and into surrounding counties. Had I been at my office computer I would have “snagged” the temperature map, but I am sure another clear cold night without cloud cover will happen again in the next 2-3 months.

[unome]

great write up by Jeff, thanks for that, srain

hgx also has a link posted on their front page for freeze info, good stuff

http://www.srh.noaa.gov/hgx/?n=freeze_info

[Ptarmigan]

A very informative evening briefing from Jeff:

First freeze of the winter season recorded at IAH this morning with the temperature falling to 32. Very interesting pattern of low temperatures outlined the urban sprawling across Harris and surrounding counties this morning defining heat corridors from development patterns. I will touch on this more below.

Temperatures have tumbled this evening with excellent radiative conditions in place. IAH fell 13 degrees since the sun has set from 53 to 40. Dewpoints currently in the upper 20’s and low 30’s support another freeze and this is favorable given this is night two after cold frontal passage which tends to be the coldest night. However the axis of the arctic surface high is centered in the Beaumont and Lake Charles area and surface observations show southerly winds across at least the western half of SE TX which suggest the temperature tumble will be halted as warmer air is brought inland from the Gulf of Mexico. With that said, would not be surprised to see temperatures approach freezing around midnight or shortly after along and northeast of US 290 and then rise some toward morning. It is very possible it will be colder at 1000pm tonight than at 600am tomorrow morning.

Sustained warming trend will begin on Wednesday after over a week of well below normal temperatures. In fact the gravity of this cold air outbreak can be noted in the record low recorded at Amarillo this morning of 5 degrees and across the nation with nearly 50% of the country with snow cover (33% is average on Christmas Day). The entire state of OK was covered in snow yesterday morning and Dallas recorded a record snow amount of a trace on Monday morning with many locations over N TX having a dusting of snow. Currently November 2014 is running an astounding 8.0 degrees below average for Houston and is currently ranked as the 9th coldest November on record. While a colder and wetter than normal winter is expected across the southern plains, the current cold air outbreak has little bearing on what the rest of winter may exhibit especially with respect to any sustained severe cold air outbreaks and one should be cautious in drawing any conclusions from the recent cold spell and how the rest of winter may play out.

As the large arctic high moves eastward southerly onshore winds will begin to promote moisture return northward. A coastal surface trough will form off the lower TX coast Wednesday and help sling moisture over the top of the surface cold dome. This will result in an increase in cloud cover and can many times slow air mass modification. Chances for rain return by Thursday as a lead short wave in the developing flow aloft moves across TX and interacts with the developing moisture return. Warm front should move inland on Friday with scattered showers continuing to stream northward off the Gulf. Temperatures will warm into the 70’s south of the warm front and dewpoints will rise into the low to mid 60’s. While normally November is not a big sea fog month along the upper TX coast, the recent cold has chilled the bay and nearshore waters into the 50’s. With dewpoints rising into the 60’s or above that of the water temperatures, sea fog will be possible Friday afternoon into Saturday.

Saturday:
Strongly dynamic storm system suggested by model guidance for this Saturday with potential threats for both severe weather and heavy rainfall. Powerful short wave will dive into the southern jet and eject rapidly out of New Mexico into TX on Saturday while the system takes on a slight negative tilt or from SE to NW which suggest little to no SW flow in the mid levels to cap off the air mass. Mid level temperatures look very cool with the storm system which will help promote an unstable air mass only with surface temperatures in the 70’s. Low level shear values look favorable for updraft rotation. Main severe limiting factor at the moment looks to be instability (CAPE of 500-1000 J/kg) across the area. SPC has already highlighted all of SE TX for a severe risk on Saturday with damaging winds and tornadoes likely being the main threats. The far southward placement of the core dynamics with this system suggest a threat is justified. It should be noted that October and November are our secondary severe weather season in SE TX and one of our worst tornado outbreaks ever recorded happened on November 21, 1992 when 4 large supercell thunderstorms produced 6 long tracked tornadoes across Harris County including a devastating ¾ of a mile wide F4 tornado in Channelview. The rest of the week focus will be on the Saturday system and its potential impacts.

The Urban Heat Core:
It has been known for a long time that urban sprawl can alter temperature and weather patterns on local scales. This was first studied in Atlanta in the 1990’s when it was noticed that unusually heavy rainfall was occurring in the late night hours during the summer months. Houston has been no exception to urban development especially on its west and northern flanks in the last few decades and is very clearly noted on clear and cold nights such as last night. Technology and the plethora of temperature data now available between official reporting sites gives a glimpse into just how widely varying the temperatures extremes can be over just a few miles. Low temperature data last night showed very interesting patterns of significantly warmer temperatures along I-10W, US 59S, I-45N, and along HWY 6 between US 290 and I-10. Temperatures along these “urban corridors” ranged anywhere from 3-8 degrees warmer than temperatures only a few miles away. What was striking is how closely the temperature patterns mirrored the major freeways and how “warm” western Harris County temperatures were especially in the Hwy 6 corridor. These observations are far from scientific as the various sensors being reported from home temperature gages are surely not all uniform nor likely all installed equally. Additionally, many of these sensors are likely within subdivisions which already create a warmer background temperature effect so the data set is not easily ready for direct comparison. Another consideration last night was the high clouds which crossed the area and what affect that may have had on the low temperature patterns. A better case could probably be made for tonight if winds were not shifting to the south late.

What can be drawn from the data is that urbanization is certainly resulting in warmer temperature readings especially under strong raditional cooling conditions. It is also noted that significant temperature differences over a very short distance are almost certainly creating microscale surface temperature boundaries during the warmer season which could help foster thunderstorm development. These boundaries are likely on the order of a few miles long and maybe less than 1/4th of a mile wide which cannot be detected on Doppler radar nor high resolution model guidance, but given the temperature discontinuity noted in the data on a clear cold night suggest a similar pattern is likely present on a hot summer day. It is likely that the climate record at BUSH IAH is starting to be skewed due to urban development surrounding the airport with Hooks (Tomball) likely a more representative station for the remaining rural areas of Harris County. The urban heat core has loosely been defined as the area within the 610 loop, but it is clear that development has been sustained enough to likely expand that area to include areas inside Beltway 8 and also to include areas near/along the major freeway systems. It is almost certain that construction of the Grand Parkway system and its resultant urban development along that system will expand the urban heat core outward to the far outer reaches of Harris County over the next decade and into surrounding counties. Had I been at my office computer I would have “snagged” the temperature map, but I am sure another clear cold night without cloud cover will happen again in the next 2-3 months.

Tornado outbreaks happened in November 1993 and 2003. Flooding has happened in November 1940, 1985, and 2004. November is quite a stormy month like October and Spring. Like Spring, Fall is a transitional season.