January: Increasing Clouds/Rain & Warmer To End Month

[srainhoutx]

HGX afternoon forecast discussion is out with a lot of information concerning our weather event in the coming week. This may well be one of those situations where you want to let your family and friends know that may not be so weather wise, IMO...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
353 PM CST SUN JAN 22 2012

.DISCUSSION...
SOUTH TO SOUTHWEST WINDS CONTINUE TO BE GUSTY ACROSS SOUTHEAST
TEXAS THIS AFTERNOON AS STRONGER WINDS FROM ALOFT MIX DOWNWARD. A
FEW SHOWERS HAVE TRIED TO DEVELOP ACROSS THE EASTERN HALF OF THE
REGION THIS AFTERNOON BUT THE CAP HAS HELD OUT ACROSS THE REGION
AND NOT EXPECTING ANYTHING MORE THAN A FEW DROPS OF RAIN OUT OF
ANY OF THE ACTIVITY TODAY. FRONTAL BOUNDARY WILL MOVE THROUGH THE
AREA AFTER MIDNIGHT BRINGING SLIGHTLY DRIER AIR INTO THE REGION
FOR MONDAY.

THE WEATHER WILL BECOME MUCH MORE ACTIVE FOR THE MIDDLE OF THE
WEEK AS A STRONG UPPER LEVEL TROUGH DIGS INTO SOUTHERN NEW MEXICO
AND BEGINS TO APPROACH THE REGION ON TUESDAY. MOISTURE WILL SURGE
NORTHWARD ACROSS THE REGION ON TUESDAY AHEAD OF THIS FEATURE AND
HAVE INCREASED POPS ACROSS THE ENTIRE REGION FOR TUESDAY. THE
HEAVIEST RAINFALL WILL OCCUR FROM LATE TUESDAY EVENING THROUGH
EARLY WEDNESDAY AFTERNOON AS A SURFACE LOW DEVELOPS ACROSS THE
LOWER RIO GRANDE VALLEY AND EXPANDS EASTWARD AS AN ELONGATED
SURFACE TROUGH ACROSS THE CENTRAL TEXAS COAST. STRONG UPPER LEVEL
FLOW ALONG THE AXIS OF THIS TROUGH AND PW VALUES OF BETWEEN 1.6
AND 1.8 INCHES WILL ALLOW FOR A THREAT OF HEAVY RAINFALL ACROSS
ALL OF SOUTHEAST TEXAS ON WEDNESDAY MORNING. MODEL QPF OUTPUT HAS
RAINFALL AMOUNTS OF 2 TO 4 INCHES DURING THIS PERIOD WITH THE GFS
EVEN HAVING A FEW 4 TO 6 INCH TOTALS ACROSS OUR NORTHERN
COUNTIES. IN ADDITION TO THE HEAVY RAINFALL THREAT SOME
THUNDERSTORMS MAY BE SEVERE WITH ISOLATED TORNADOES BEING THE
PRIMARY THREAT. A STRONG LOW LEVEL JET AND BACKED SURFACE WINDS
WILL PRODUCE 0-3 KM HELICITY VALUES IN EXCESS OF 250 ACROSS THE
REGION WEDNESDAY MORNING WITH LI VALUES OF BETWEEN -2 AND -4.
INSTABILITY WILL BE SOMEWHAT LACKING WITH CAPE VALUES OF BETWEEN
500-800 ACROSS THE REGION. HAVE NOT INCLUDED MENTION OF SEVERE IN
THE GRIDS AT THIS TIME BUT THIS MAY NEED TO BE ADDED IF THE THREAT
CONTINUES TO BECOME MORE WELL DEFINED.

THE RAINFALL WILL END FOR MOST OF THE REGION WEDNESDAY NIGHT AS A
COLD FRONT MOVES THROUGH THE REGION. WILL KEEP SOME POPS IN FOR
THE NORTHERN COUNTIES THROUGH THURSDAY TO ACCOUNT FOR ANY LIGHT
WRAP AROUND PRECIPITATION AS THE UPPER LOW CROSSES THE REGION.
DRIER WEATHER WILL BE ON TAP FOR FRIDAY AND SATURDAY WITH ONSHORE
FLOW RETURNING BY SUNDAY.

[jasons2k]

Linked on The Chronicle's home page now:
http://blog.chron.com/sciguy/2012/01/lo ... this-week/

[Portastorm]

@Jason -- that sounds like one crazy weather day. I cannot imagine what that must have been like, but admittedly, I wouldn't mind experiencing it sometime! My high school senior has Tech high on his list so who knows, maybe I will! LOL.

Meanwhile, yesterday I was chirping on this forum about my local NWSFO (EWX-Austin/San Antonio, located in New Braunfels) and how I couldn't understand why they were looking at rainfall amounts much less than what model guidance was spitting out. This snippet from this afternoon's discussion answers it, I guess. We in the Austin area are supposed to get roughly 2 inches or less per our NWS.

FORECAST QPF PERHAPS SHOWS SLIGHTLY MORE RAIN THAN IS ACTUALLY EXPECTED...BUT THIS IS DUE TO THE 24 HOUR WINDOW OF HIGHER POPS WHICH COULD SHRINK IN TIME AS CONVECTIVE FOCUS NARROWS.

[niner21]

I'll bet that we get a dusting of rain and that's it.

[Andrew]

GFS comes in a little faster compared to the 12z mainly due to the fact that the ULL never full detaches from the energy up north. That shifts the higher QPF totals farther to the east.

[srainhoutx]

The SPC issues Slight Risk for Central and parts of S Texas in their new day 2 outlook...

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CST MON JAN 23 2012

VALID 241200Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF CENTRAL AND
SRN TX...

...SYNOPSIS...
AS A NRN STREAM UPPER TROUGH CONTINUES EWD ACROSS ERN CANADA AND THE
NERN U.S. THIS PERIOD...A SECOND TROUGH OVER THE DESERT SW IS
FORECAST TO MOVE SLOWLY EWD ACROSS THE SRN ROCKIES AND INTO THE SRN
PLAINS.

AT THE SURFACE...A COLD FRONT ASSOCIATED WITH THE NERN U.S. TROUGH
SHOULD BE SHIFTING OFF THE NEW ENGLAND AND MID-ATLANTIC COASTS AT
THE START OF THE PERIOD...BUT WILL LAG WSWWD/WWD ACROSS THE GULF
COAST REGION. ALONG THE WRN FRINGE OF THIS BOUNDARY -- I.E. INVOF
THE RIO GRANDE...EXPECT THE UPPER TROUGH APPROACHING THE S CENTRAL
CONUS TO DRIVE FRONTAL CYCLOGENESIS -- WITH A WEAK LOW MOVING
INTO/ACROSS S TX THROUGH THE END OF THE PERIOD.

...CENTRAL AND SRN TX...
SELY LOW-LEVEL FETCH OFF THE GULF OF MEXICO WILL SUPPORT
BOUNDARY-LAYER MOISTENING ACROSS TX THIS PERIOD...WITH 50S DEWPOINTS
REACHING AS FAR NWWD AS THE TRANSPECOS REGION AND TX S PLAINS.
WHILE WEAK ELEVATED INSTABILITY AND LOW-LEVEL WARM ADVECTION WILL
LIKELY SUPPORT CONVECTIVE DEVELOPMENT ACROSS CENTRAL AND N TX
EARLY...LITTLE SEVERE THREAT IS EVIDENT WITHIN THIS REGIME.
HOWEVER...AS COOLING ALOFT ASSOCIATED WITH THE UPPER TROUGH
OVERSPREADS THE MOISTENING BOUNDARY LAYER...AN ENVIRONMENT
THERMODYNAMICALLY SUPPORTIVE OF MORE ROBUST/SURFACE-BASED CONVECTION
WILL EVOLVE. AFTERNOON CONVECTIVE DEVELOPMENT SHOULD OCCUR -- AIDED
BY LARGE-SCALE UVV IN ADVANCE OF THE UPPER SYSTEM -- E OF THE
TRANSPECOS REGION INTO PORTIONS OF CENTRAL TX. WITH SHEAR
SUFFICIENT FOR ORGANIZED/SUPERCELL STORMS...THREAT FOR ISOLATED
DAMAGING WINDS AND HAIL -- AND POSSIBLY A TORNADO -- SUPPORTS
INCLUSION OF SLIGHT RISK ACROSS THIS AREA.

THE SLIGHT RISK WILL ALSO BE EXTENDED EWD TO THE MIDDLE TX
COAST...WHERE EARLIER/SLIGHTLY ELEVATED CONVECTION WHICH WILL LIKELY
HAVE SHIFTED NWD MAY BE REPLACED BY ISOLATED/SURFACE-BASED STORMS AS
THE SURFACE LOW DEVELOPS ESEWD. HERE...ISOLATED STRONG GUSTS AND A
TORNADO OR TWO MAY ACCOMPANY A FEW STRONGER/ROTATING CELLS THROUGH
THE END OF THE PERIOD.

[srainhoutx]

The 06Z GFS is back with a closed core low over S Texas and is a bit slower. Heavy rains/storms are a bit further W on Tuesday and some 'cooler air' is now suggested NW of the U/L suggesting some. Possible wintry mix for southern New Mexico and W TX behind the ULL. The U/L low and Coastal low both pass near SE TX late Wednesday/early Thursday suggesting 2-3 inch rainfall with isolated 4+ amounts N and E of Metro Houston. The Euro remains very wet as well and severe storms appear possible during the day on Wednesday. We'll see if the SPC expands the Slight Risk further E in time as the dynamics still appear very impressive with high pw's of 1.7 which is 2 standards above normal for January and instability is still impressive across the eastern half of Texas and points E. All that said, it does appear the best chance for the heaviest rains will be along and N of the HWY 59 corridor for this event and hopefully those that missed out on January 9th will do better in the rainfall department. IAH is running behind while Hobby is ahead for the month of January. We'll see how all this plays out later today and Tuesday evening into Wednesday does appear to be rather active across the area.

[jasons2k]

During my walk yesterday, I noticed the maple and ash trees are already blooming. I even saw a couple of Azaleas with some blooms. Crazy!

[srainhoutx]

Morning e-mail from Jeff:

Highly active storm system will move into to Texas mid week to produce the threat for severe weather and excessive rainfall.

Short Term (Today-Tuesday AM):
Pacific cold front responsible for the massive western TX wind/dust event yesterday is pushing off the coast this morning with a much drier air mass building into the nearshore waters ending the sea fog that has plagued the area since last Friday. NW winds today will help push drier NC TX air mass into the region, but this will be short lived as the central US high pressure cell moves quickly eastward and low pressure develops in the lee of the southern Rockies. Winds will turn east by late tonight with clouds increasing.

Tuesday Afternoon-Wednesday Afternoon:

Severe weather and heavy rainfall possible.
Powerful upper level trough will drop into northern Mexico which in turn forces downstream pressure falls over southern TX early Tuesday. Surface low pressure will develop across the SW Rio Grande plains and help promote a rapidly intensifying low level jet across TX from the western Gulf toward DFW. Models are in agreement that the low level jet will increase to near 40kts by Tuesday afternoon pumping copious Gulf moisture from the western Gulf into the coastal bend and then northward into central and SE TX. Old frontal boundary offshore from today will retreat northward as a warm front. Combination of this boundary, increasing large scale ascent from the upper level storm, and strong warm air advection regime all point to showers/thunderstorms developing near/north of this boundary on Tuesday. Forecast models show low level winds backing during the afternoon toward the ESE while mid level WSW flow increases…this will begin to create favorable low level turning of winds. Current thinking is that instability will be limited, but given the strong low level shear that will be developing supercell structures may begin to develop within northward moving cells off the Gulf.

Entire area should become warm sectored by Tuesday evening, but showers and thunderstorms will continue to stream northward out of the Gulf of Mexico in SSW to NNE lines. Cold front and main lift will begin to impinge on the area after midnight along with favorable jet dynamics as the upper low wobbles into western TX. Expect a line of strong thunderstorms to move ESE out of central TX into very favorable low level inflow. Main concern overnight into Wednesday morning will be the threat for supercells moving northward out of the Gulf and embedded supercells in the main line approaching from the west. These cells will have the threat to produce low level rotation and possible tornadoes. Low LCL’s and high moisture levels will result in very low cloud bases and any tornadoes will likely be wrapped in rain. Warning lead times in these sort of situations tend to be lower than average and heavily radar based. All severe modes will be possible: large hail, damaging winds, and tornadoes from late Tuesday through early afternoon Wednesday. SPC has outlooked a large part of the coastal bend, SE TX, and central TX for severe thunderstorms (see attached map below).

Surface low stretches out to the northeast Tuesday night while strong low level jet remains anchored off the western Gulf pumping rich moisture northward. PWS increase to 1.46 in on the GFS by early Wednesday morning and near 1.55 in by Wednesday midday which is nearing the 99th percentile and +2 SD for late January moisture levels. This high moisture combined with the threat for storm cells to become parallel to the mean steering wind flow raises an excessive rainfall/flash flood red flag. Other potential will be for large supercells to slow/anchor in the strong low level flow producing extremely high rainfall rates in a very short period of time. Air mass will be capable of some 2-3 inch per hour rainfall rates which can create problems very quickly in urban areas. Expect widespread 1-2 inches of rainfall with isolated totals of 3-5 inches. Main axis of excessive rainfall currently appears to focus along and north of a line from Victoria to Conroe to Lufkin, but any southward shift in this axis would bring the core of the excessive rainfall along the US 59 corridor and into the more urban areas. As noted with the 1-9-12 event high short term rainfall rates can result in significant street flooding in a very short period of time. DO NOT drive into high water!

Long Term (Wednesday night-Friday)
Upper level storm system will slowly progress across the state, but the main trigger for showers and thunderstorms should move eastward into Louisiana by early Wednesday evening. Cold front will move off the coast at this point and while a few showers may linger into Thursday and severe and heavy rainfall threat will be over. Colder air mass will filter southward and the GFS model is showing a period of trapped low level moisture under the frontal inversion leading to possibly an extended period of low level clouds. May not see any sun on Thursday which will keep highs on the colder side. Should see the low level deck break out on Friday, but I am sometimes wary of moisture trapped under the frontal inversion as it can be difficult to scour out the low clouds.

[MontgomeryCoWx]

excited for this storm... if we're going to have this oppressive winter heat, we might as well throw some severe weather in there with heavy rains.

[wxman57]

During my walk yesterday, I noticed the maple and ash trees are already blooming. I even saw a couple of Azaleas with some blooms. Crazy!

You're probably seeing the smaller Encore azaleas in bloom, not the larger varieties that typically bloom in later March and April. My Encore azaleas are in full bloom, but they're in bloom most of the year. My larger (non-Encore variety) azaleas are showing no signs of blooming.

Sure is great winter weather, though. Nice to be able to bike in short sleeves in January, though I was a little bit cool yesterday afternoon with the clouds and upper 70s.

There's really no way to tell what areas are going to be hardest hit by rain on Wednesday. It all depends on where the training echoes set up. Could be north of 59, could be to the south again.

[txflagwaver]

So biggest threat for severe weather Tuesday night to Wednesday morning??

[srainhoutx]

So biggest threat for severe weather Tuesday night to Wednesday morning??

Much hunch is an early morning Wednesday throughout the day. This will be another one of those hour by hour, minute by minute type events similar to what we saw on January 9th. The one thing that is different, is this system appears to be stronger with better dynamics and higher available moisture.

[tireman4]

PW rates of 1.55 in January. Goodness gracious.

[MontgomeryCoWx]

Whats the mean PW rate in January for Houston?

[txflagwaver]

Early morning 6am or early morning 2am?

[jasons2k]

You're probably seeing the smaller Encore azaleas in bloom, not the larger varieties that typically bloom in later March and April. My Encore azaleas are in full bloom, but they're in bloom most of the year. My larger (non-Encore variety) azaleas are showing no signs of blooming.

Sure is great winter weather, though. Nice to be able to bike in short sleeves in January, though I was a little bit cool yesterday afternoon with the clouds and upper 70s.

There's really no way to tell what areas are going to be hardest hit by rain on Wednesday. It all depends on where the training echoes set up. Could be north of 59, could be to the south again.

I think they were - they were the smaller variety. I have another neighbor with a yard full of traditional azaleas and they are not blooming at all.

I just hope we don't get dry-slotted on Wed afternoon like the NWS was hinting at. Seems to happen more often than not.

I'm with you on the warmth. This pattern is more like March than January.

Did anyone else notice all the dust in the air this morning?

[svrwx0503]

Whats the mean PW rate in January for Houston?

The link below has a nice statistical breakdown of PW values from all of the radiosonde sites around the Nation. Unfortunately there is no site for Houston but I think the Lake Charles data would be a close enough representation of what we see here locally on average.

http://www.crh.noaa.gov/unr/?n=pw

As you can see from the LCH data, PW's around 1.50'' would be 2SD above normal and with several models forecasting values to possibly peak around 1.55-1.6'' that would put the values around the 99th percentile.

[srainhoutx]

Early morning 6am or early morning 2am?

Exactly at 2:38.25 AM...lol... your guess is as good as mine...

[Big O]

With respect to longer range, the models are all over the place with respect to the teleconnection indices. I tend to side with the European, which at 0z has a slightly negative NAO, slightly negative AO, and negative EPO at days 8-10. What we need is a +PNA to get things going, but I see nothing to suggest that will come to fruition, yet. Perhaps Srain can offer some words of wisdom and HOPE.