May 2016: Shower/Storm Chances To End May

[jasons2k]

Hi-res radar shows some sort of E-W boundary skipping rapidly north across Montgomery County. Not sure what it is, maybe a subtle wind shift or mid-level boundary being picked-up...

Edited: On satellite it looked like the clearing line, too.

[srainhoutx]

Interesting to see such an anomalous cold signature across the Northern 2/3rds of the United States and likely a myriad of embedded disturbances riding along a stalled frontal boundary across portions of Texas, Arkansas and Louisiana.

[Katdaddy]

An awesome weather perspective from the radar, satellite, and the surface this evening. Looking W from League City, TX you can see streaming cirrus along the horizon from a cluster of severe storms in MX to the SW of Eagle Pass across the Rio Grande 380 miles away. Impressive.

[Ptarmigan]

Interesting to see such an anomalous cold signature across the Northern 2/3rds of the United States and likely a myriad of embedded disturbances riding along a stalled frontal boundary across portions of Texas, Arkansas and Louisiana.

05102016 CPC Day 8+ Analogs 610analog_off.gif

05102016 CPC Day 6 to 10 610temp_new.gif

05102016 CPC Day 6 to 10 610prcp_new.gif

Some these analog dates had heavy rain within two weeks of the date, like 2000, 2001, and 2006.

Heavy rain fell on May 19, 2000, June 5-9, 2001 (Allison), and Memorial Day 2006.

[brooksgarner]

Late season cold front around May 20th? EURO is really gunning for it. Maybe there's hope that we're not quite stuck in the summer-long humidity quite yet.

[srainhoutx]

Appears the major upgrade of the GFS went very smoothly and seamlessly with the 12Z output. This smooth transition is due to increased computing power with finer resolution sets the stage for another major upgrade to the HWRF Hurricane modeling system scheduled for early June.

Regarding that potential early next week cold front, not sure it will sweep all the way to the NW Gulf. The Central and Eastern areas of the Gulf Coast looks like a better solution since the coldest air will be well North and East of Texas. There may well be a frontal boundary stalled across portions of East/SE Texas that could be a focal point for training storms Sunday into Tuesday.

[unome]

Mixed Case

http://forecast.weather.gov/product.php ... roduct=AFD

[Katdaddy]

Another warm and muggy afternoon with a slight chance of thunderstorms across SE TX today. Slight thunderstorm chances to continue overnight and into Friday morning as a slow moving cool front drifts across the area. Saturday looks to be a nice day before additional thunderstorms chances arrive Sunday afternoon.

[srainhoutx]

Thursday morning briefing from Jeff:

Highly active weather pattern for the next week or longer….

Upper air pattern similar to 2015 in place over the southern plains with almost daily complexes of thunderstorms across TX. Overall trend over the next several days will be for surface boundaries and upper level disturbances to move closer and closer to SE TX and likely help generate convection with the help of daytime heating and a moist and unstable air mass.

Weak surface front over N TX this morning will edge southward into SE TX this afternoon. A few strong to severe thunderstorms will be possible along this feature late this afternoon from College Station to Lake Livingston. This weak boundary will sag toward the coast overnight with at least a chance of showers and thunderstorms as it progresses southward through the area. Boundary will push off the coast Friday morning with a slightly drier air mass moving into the region. This drying will be short lived and expect a humid air mass to return quickly on Saturday as the coastal boundary dissipates.

Forecast model disagreement increases late weekend into early next week as the next large scale storm system drops into the SW US and begins to eject disturbances across TX. Sunday night into Monday morning is potentially an active period with both the CMC and ECMWF showing a slow moving complex of thunderstorms across SE TX. There is certainly a heavy rainfall signal with 20-30kts low level inflow and PWS of 1.8 inches, but the GFS models is capped and dry during this period leading to low confidence. IF the GFS begins to trended wetter and toward the CMC and ECMWF then the potential for a heavy rainfall event will increase during this time period.

Pattern remains unsettled into next week with general troughing out west and disturbances moving across the region producing complexes of thunderstorms. Gulf of Mexico seems fairly wide open through the entire period supplying plentiful moisture. There appears little change in this overall pattern into late May and TX will remain under the threat for both severe weather and flooding rainfall likely late into this month.

Similar patterns such as the current pattern have produced some significant severe weather and flash flood events in May 2015, May 2006 and May 2000.

[brooksgarner]

srainhoutx -- Great research into the analogues from may 2015, 2006 and 2000! Thanks!

[srainhoutx]

Thanks Brooks. One of the things I am watching is the trends that the off hour 06Z GFS 'sniffed' out particularly early next week. Will need to monitor the future trends for a potential Mesoscale Convective System possibly organizing over the Hill Country and moving SE toward the Upper Texas Coast next Tuesday. If the future runs of the GFS concur with the activity the ECMWF and the Canadian Global models are picking up on. Water vapor imagery does show at least two upper lows slowly moving East over the Pacific. As wave lengths slow down as we near our typical summertime pattern, those upper air features and any embedded shortwaves or wrinkles in the mean flow as well as abundant tropical moisture from the Eastern Pacific and the Western Caribbean could enhance shower/thunderstorm development where any boundaries stall or cold pooling becomes established particularly to our N and W. Thankfully we have had time to dry out for a couple of weeks. That may help in reducing any threat of a Regional Flooding beyond normal urban street flooding where heavier rainfall may occur. Looks like an active and unsettled pattern may well develop in the days ahead.

[brooksgarner]

Look at that moisture slug moving our way from the Gulf... high PWATS interacting with stalled frontal boundary? Hmmmm.

Here's a map I just put together for Sunday... Stalled front may focus a few meso convective systems Sunday-Thursday next week. Hard to forecast meso stuff, but that's the nature of this beast. Any one of those could flood us.

Fronts_Forecast.png

[srainhoutx]

Afternoon updated quantitative precipitation forecast valid through next Thursday.

[Ounce]

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
753 PM CDT THU MAY 12 2016

TXZ213-130145-
HARRIS TX-
753 PM CDT THU MAY 12 2016

...STRONG THUNDERSTORMS ACROSS CENTRAL HARRIS COUNTY THROUGH 845 PM
CDT...

AT 753 PM CDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM OVER
EASTERN ADDICKS PARK TEN...MOVING NORTHEAST AT 10 MPH.

HALF INCH HAIL AND WINDS IN EXCESS OF 30 MPH WILL BE POSSIBLE WITH
THIS STORM.

LOCATIONS IMPACTED INCLUDE...
JERSEY VILLAGE...HUNTERS CREEK VILLAGE...BUNKER HILL VILLAGE...PINEY
POINT VILLAGE...SPRING VALLEY...NORTHSIDE / NORTHLINE...SPRING BRANCH
WEST...ALDINE...ELDRIDGE / WEST OAKS...GREATER GREENSPOINT...SPRING
BRANCH NORTH...ADDICKS PARK TEN...MEMORIAL PARK...GREATER HEIGHTS...NEAR
NORTHSIDE HOUSTON...GREATER FIFTH WARD...HEDWIG VILLAGE...HILSHIRE
VILLAGE...WILLOWBROOK AND ACRES HOME.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

FREQUENT CLOUD TO GROUND LIGHTNING IS OCCURRING WITH THIS STORM.
LIGHTNING CAN STRIKE 10 MILES AWAY FROM A THUNDERSTORM. SEEK A SAFE
SHELTER INSIDE A BUILDING OR VEHICLE.

&&

LAT...LON 2980 9526 2972 9565 2976 9573 2978 9571
2982 9571 2988 9567 2994 9565 3004 9554
2995 9540
TIME...MOT...LOC 0053Z 232DEG 7KT 2982 9561

$$

[Ptarmigan]

Look at that moisture slug moving our way from the Gulf... high PWATS interacting with stalled frontal boundary? Hmmmm.

Here's a map I just put together for Sunday... Stalled front may focus a few meso convective systems Sunday-Thursday next week. Hard to forecast meso stuff, but that's the nature of this beast. Any one of those could flood us.

Fronts_Forecast.png

I have seen flood events in this type of setup.

[srainhoutx]

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
759 PM CDT THU MAY 12 2016

THE NATIONAL WEATHER SERVICE IN LEAGUE CITY HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
CENTRAL HARRIS COUNTY IN SOUTHEASTERN TEXAS...

* UNTIL 830 PM CDT

* AT 759 PM CDT...A SEVERE THUNDERSTORM WAS LOCATED OVER GREATER
INWOOD...OR NEAR JERSEY VILLAGE...MOVING NORTHEAST AT 25 MPH.

HAZARD...60 MPH WIND GUSTS AND QUARTER SIZE HAIL.

SOURCE...RADAR INDICATED.

IMPACT...HAIL DAMAGE TO VEHICLES IS EXPECTED. EXPECT WIND DAMAGE
TO ROOFS...SIDING...AND TREES.

* LOCATIONS IMPACTED INCLUDE...
HUMBLE...JERSEY VILLAGE...SPRING...SPRING BRANCH WEST...ALDINE...GREATER
GREENSPOINT...SPRING BRANCH NORTH...ADDICKS PARK TEN...NORTHERN
NORTHSIDE / NORTHLINE...KINGWOOD...WILLOWBROOK...ACRES HOME...FAIRBANKS
/ NORTHWEST CROSSING...GREATER INWOOD...WESTBRANCH...HIDDEN VALLEY...
SPRING BRANCH CENTRAL...BUSH INTERCONTINENTAL AIRPORT...SPLASHTOWN
AND CARVERDALE.

[Katdaddy]

With 1983 being an analog year for the upcoming 2016 hurricane season; it brought back some weather memories this evening. 33 year's ago we were also transitioning away from an active El Nino. I remember May 83 very well for the May 19-21st severe weather event across SE TX. The NW and N side of Houston had streaks of damaging downburst winds gusting to 100MPH. An active 2 weeks of weather ahead for TX beginning Sunday afternoon so enjoy the nice weather tomorrow afternoon and Saturday. Here are some scanned images of the 1983 Texas Severe Thunderstorm Outbreak, May 19-21, 1983 analysis report from the NSSFC and NWS.

[srainhoutx]

The overnight guidance continues to advertise an active weather pattern developing Sunday through next Friday. Rounds of showers and heavy thunderstorms are a possibility as a slow moving frontal boundary draped across the Region with embedded upper air disturbances rotating around a very deep NE trough and yet another slow moving Western upper low organizes creating a very unsettled pattern. PW's are expected to increase to near 2 inches suggesting a potential risk for excessive rainfall rates. Those storms appear to be slow movers and could be capable of dropping 2-3 inch per hour rainfall rates. Since it appears that storm development will be mesoscale driven, it is impossible to know where, when and how much rainfall any particular neighborhood can expect. Will go with an Area Wide 2-4 inches with isolated higher amounts of 5-7 inches possible as of this morning. We will need to monitor the future guidance carefully throughout the weekend into early next week as this will be a challenging and complicated forecast.

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CDT FRI MAY 13 2016

VALID 161200Z - 211200Z

...DISCUSSION...
A MODESTLY PROGRESSIVE SOUTHERN STREAM IN CONJUNCTION WITH A
MOIST/POTENTIALLY UNSTABLE AIR MASS NEAR/SOUTH OF A SLOW-MOVING
FRONT SHOULD RESULT IN MULTIPLE DAYS OF SEVERE THUNDERSTORMS ACROSS
THE SOUTH-CENTRAL TO SOUTHEAST CONUS NEXT WEEK...ALTHOUGH
PREDICTABILITY IS LIMITED REGARDING SOME OF THE MESOSCALE-RELATED
SPATIAL DETAILS.

FOR DAY 4/MONDAY...THE MAIN SEVERE RISK SHOULD BE FOCUSED ACROSS THE
SOUTH-CENTRAL HIGH PLAINS TO THE EAST OF A SURFACE LOW AND NEAR A
FRONT...ALTHOUGH SOME NORTH/SOUTH-SPATIAL VARIABILITY EXISTS AMONG
AVAILABLE GUIDANCE AS FAR AS THE PEAK SEVERE RISK.

DAY 5/TUESDAY...CURRENT THINKING IS THAT THE MAIN SEVERE POTENTIAL
WILL BE ACROSS TX...ESPECIALLY A LARGE PART OF CENTRAL AND EAST TX
AND POSSIBLY OTHER PARTS OF THE ARKLATEX/LOWER MS RIVER VALLEY...AS
A COLD FRONT STEADILY MOVES SOUTHEASTWARD. NEAR/AHEAD OF THE
FRONT...A COMBINATION OF AMPLE MOISTURE AND MODERATE TO STRONG
BUOYANCY IN THE PRESENCE OF MODEST VERTICAL SHEAR COULD SUPPORT
SCATTERED SEVERE THUNDERSTORMS CAPABLE OF SEVERE HAIL AND WIND.

DAY 6/WEDNESDAY...AS THE FRONT CONTINUES SOUTHWARD ACROSS TX...THE
RISK FOR SEVERE THUNDERSTORMS MAY SHIFT INTO SOUTH/WEST TX...WITH
OTHER SEVERE THUNDERSTORMS POSSIBLE AS FAR EAST AS THE TN VALLEY AND
CAROLINAS IN VICINITY OF THE FRONT.

..GUYER.. 05/13/2016

[srainhoutx]

Friday morning briefing from Jeff:

***Active weather the next several days will bring several rounds of thunderstorms to the region***

Large scale upper air pattern will bring several storm systems across TX over the next 5 days each of which will produce a chance of heavy rainfall and severe weather.

Surface boundary has stalled this morning from Victoria to Pearland to Orange and may drift a few more miles southward. Strong surface heating will result in the “cooking” of this boundary and once temperatures reach the mid 80’s and the seabreeze begins to advance inland from the Gulf expect storms to fire along the seabreeze and old frontal zone. Weak steering flow again today will produce slow storm motions with rainfall of 1-2 inches in an hour or less. Instability will also be high once peak heating is reached with hail and damaging winds possible from pulse severe storms.

Saturday:
Another frontal boundary approaches from the north and slows into our northern counties by late afternoon. Air mass becomes unstable and expect storms to develop both along the front and the inland moving seabreeze. An isolated severe storm will be possible during this period also with large hail and gusty winds the main threats.

Sunday-Monday:

***Active period with flash flooding possible***

Weak frontal boundary stalls over the region on Sunday while a strong upper air disturbance approaches from the west Sunday afternoon and evening. Expect thunderstorms to develop both along the front and across the TX Hill Country and move into SE TX. Parameters are pointing toward 20-30kts of low level Gulf inflow, surging moisture levels, good low level focus with a boundary in place, and decent upper level venting suggestive of slow moving heavy rainfall.

Will need to watch this period very carefully for a slow moving or stalling thunderstorm complex with high intensity rainfall rates. Much will be focused on the meso scale so there is only so much confidence at this time…but the overall pattern looks favorable for heavy rainfall.

Wednesday-Thursday:

***Active period with flash flooding and severe weather possible***

Another strong disturbance will impact TX during this period with a frontal boundary stalled across SE TX. SW flow aloft really increases on Wednesday and will likely support widespread thunderstorm development…some severe and some with excessive rainfall.

This is still many days away…but model agreement is there to be concerned with this period.

Hydro:

Central, north, and east TX rivers remain well above base flow with several basins in flood. Water supply and flood control lakes are full or into their flood pools from the recent rainfall. Thunderstorm complexes over N and NC TX the last few days have added more water into the upper and middle Brazos Basin and the upper Colorado Basin.

Widespread heavy rainfall over the next 5 days will once again result in rises on area rivers…some may return to flood stage.

Addicks and Barker Reservoirs in western Harris County remain elevated and additional rainfall across these watersheds could result in return flooding on recently opened roadways in and around the reservoirs.

Rainfall Amounts:
QPF has been increased overnight into the 2-3 inch range for the next 7 days with isolated higher totals likely. Much of this will fall during a couple of time periods and given the moist air mass 2-3 inches in an hour will be possible. Think amounts will need to be increased more as confidence builds on location and timing of upcoming thunderstorm complexes.

[Cromagnum]

Pretty nasty thunderstorms down near Angleton and Sweeney. Pretty intense hail.