May 2015 Record Setting May Rainfall Totals For Region

[jasons2k]

Forecast this week went from wet to dry to wet. I'm glad it's wet though, we still need all the rain we can get.

[BlueJay]

Cloudy. Sunny. Very dark and cloudy. Partly sunny. 6 rain drops.
Sprinkler time if this continues.

[srainhoutx]

The updated surface charts from the Weather Prediction Center suggests a very slow moving or stalling frontal boundary will set up shop across S Central/SE/E Texas this coming Sunday into early next week. Typically when we see such a pattern developing with a persistent onshore flow at the lower levels off of the Western Gulf as well as a robust upper low/rough to our West promoting SW flow aloft, heavy rainfall seems possible. We may see a brief break in rain chances Friday into Saturday, but even that is rather uncertain as we witnessed last night and early this morning across the Hill Country and NW of Metro Houston. Mesoscale features are very difficult to forecast and even the short term meso guidance cannot resolve such features well in advance.

[srainhoutx]

05062015 mcd0517.gif

MESOSCALE DISCUSSION 0517
NWS STORM PREDICTION CENTER NORMAN OK
0146 PM CDT WED MAY 06 2015

AREAS AFFECTED...PORTIONS OF SOUTHWEST TEXAS

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 061846Z - 062045Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...THUNDERSTORMS ARE DEVELOPING AND WILL BE EXPANDING IN
COVERAGE THROUGH THE AFTERNOON. A WEATHER WATCH IS POSSIBLE.

DISCUSSION...STRONG HEATING CONTINUES TO ERODE CONVECTIVE INHIBITION
WITH BOUNDARY-LAYER DEWPOINTS HOLDING IN THE MID-60S. SHOWERS AND A
FEW THUNDERSTORMS HAVE DEVELOPED ON THE NORTHERN EDGE OF A
PERSISTENT STRATUS FIELD OVER THE BIG BEND REGION. ADDITIONAL
THUNDERSTORMS ARE LIKELY...BOTH ALONG THE DRYLINE STRETCHING FROM
FORT STOCKTON TO MIDLAND AND POINTS NORTHEAST...AND WITHIN A
THICKENING FIELD OF CUMULUS WHERE MIXED-LAYER CAPE VALUES HAVE
INCREASED TO 1500-2000 J/KG. EFFECTIVE SHEAR VALUES OF 30-40 KT WILL
SUPPORT MULTICELL STRUCTURES WITH SOME SUPERCELL STRUCTURES LIKELY
WITH PERSISTENT UPDRAFTS. A NEGATIVE FACTOR FOR THUNDERSTORM
POTENTIAL IS A SIGNAL FOR MID-LEVEL SUBSIDENCE TO SPREAD IN FROM THE
WEST...POSSIBLY ASSOCIATED WITH THE EQUATOR-WARD SIDE OF THE
ENHANCED 400-250 MB FLOW. THE RESULTANT LOWERING OF MID-LEVEL LAPSE
RATES COULD INITIALLY LIMIT THE SEVERE POTENTIAL TO MARGINALLY
SEVERE HAIL...AND PERHAPS A FEW SEVERE WIND GUSTS GIVEN THE DRY
MID-LEVEL AIR SPREADING IN. THE TORNADO THREAT IS EXPECTED TO REMAIN
LOW INITIALLY BECAUSE OF WEAK LOW-LEVEL WINDS...AND IS EXPECTED TO
REMAIN WEAK UNTIL EARLY EVENING. THEREFORE THE INITIAL THOUGHT IS TO
ISSUE A SEVERE THUNDERSTORM WATCH IF ONE IS ISSUED...BUT THE WIND
FIELDS AND RADAR TRENDS OF THE DEVELOPING THUNDERSTORMS WILL
CONTINUE TO BE MONITORED FOR ANY UPTICK IN TORNADO POTENTIAL.

..CONIGLIO/HART.. 05/06/2015


ATTN...WFO...FWD...EWX...SJT...MAF...

[texoz]

Rough afternoon for folks in north TX, OK, and Nebraska.

Was watching one tornado chaser video from southwest of OK City. He was parked with his camera trained on another car that was 6 feet from him. The wind driven rain was so blinding I almost couldn't see the car 6 feet away. Was expecting to see it lift off the ground the wind was blowing so hard. Eventually, after the wind died down it became obvious he was parked in a gas station. Crazy video.

[srainhoutx]

The overnight guidance continues to trend toward an active unsettled pattern this weekend into next week. A very robust upper low/trough continues to dig south and should fully close off into a cold core upper low across Southern Nevada on Saturday. There are indications that a rather strong disturbance will rotate beneath the base of the trough Friday night into Saturday firing storms along the Rio Grande as well as a dryline across West Central Texas. The Storm Prediction Center has outlined a Moderate Risk for Severe Storms across portions of the Southern and Central Plains for Saturday.

By Sunday into early next week things become rather complicated as the Western upper trough takes on a negative tilt with embedded disturbances riding NE in the SW flow aloft over Texas. Add to the mix a very slow moving frontal boundary that appears to pull up stationary across portions of Central and SE Texas and you have a recipe for a heavy rainfall event. The medium to long range guidance suggests this sort of pattern may persist throughout most of next week. It is possible that we could see Flood Watches begin to be hoisted West to East across a large portion of the Lone Star State if he trends continue the next couple of days. Due to the the slow motion of any storms that develop over the weekend into next week, very heavy rainfall rates of 2+ inches per hour will need to be monitored.

[srainhoutx]

The 12Z GFS is rather insistent suggesting a very weak and defuse frontal boundary sags south across the Hill Country and basically washes the boundary out into next Thursday. Further to our West near Southern California/Arizona, the pesky upper trough remains sending ripples of upper air disturbances across the Southern half of Texas. Sunday into later next week could be rather wet and stormy, if the guidance is correct.

[srainhoutx]

The next couple of days will offer great concern for a potential severe weather outbreak across the Central and Southern Plains extending as far south as the I-20 Corridor into the Edwards Plateau.

Attention then shifts further S into the Hill Country and SE Texas as a weak stalling frontal boundary approaches the Coastal Plain Sunday afternoon into next Monday. A squall line appears likely overnight Sunday into Monday leaving a cold pool across South Central Texas extending ENE. To the West, a very pesky upper trough appears to hold strong until at least mid week. Embedded disturbances appear to ride ENE along the stalled boundary with a cold pool in place as well as left over boundaries assisting to focus bouts of heavy training storms. The QPF guidance continues to advertise rounds of strong to possibly severe storms developing every 6 hours or so training across already saturated grounds. Some of the various quantitative precipitation forecasts are suggesting 5 to 7 inches of rainfall with isolated totals approaching 11 inches. PW'S Increase to near 2 inches which raises an eyebrow. Flood and Flash Flooding concerns increase if such a scenario unfolds. The unsettled pattern may persist into late next week which is concerning. Upstream River flows are already high with almost daily flooding across NW and N Central Texas from the storms most of this week. It is difficult if not impossible to forecast various meso features beyond 6 to 12 hours, but the persistence displayed by the various computer model schemes do warrant monitoring as we enter the weekend and early next week. Stay Tuned!

[snowman65]

What is up with all this rain next week????...GEEZ...enough already

[jasons2k]

I'll take it. The trees are still under stress and recovering from the drought. Some of the pines are still going through cycles of bursting new needles with rain and them dropping them. There are still a lot in a slow decline cycle and are just now dying off.

Eric Berger's blog (it was either last Monday or the one before) had a writeup about the rain so far this year. Even with all the perceived wetness we are very close to normal. We just forgot what Houston climate is supposed to be like. And all this is with the help of El Niño. It's a little concerning about what lies ahead for us when this El Niño cycle is over. Enjoy the moisture and lack of water restrictions while we have it.

[srainhoutx]

Morning briefing from Jeff:

Significant Severe Weather/Tornado Outbreak:

Factors are coming together for a major severe weather and tornado outbreak across the southern and central plains on Saturday. Main threat region will extend from NC TX to KS. Intense supercell thunderstorms are forecasted to develop Saturday afternoon along a dry line over W OK into NC TX and move ENE Saturday evening. Wind profiles strongly support tornadic supercells with the potential for large long tracked life threatening tornadoes. This will likely be a significant tornado outbreak for OK, KS, and possibly N TX.

Day 2 (Saturday) Severe Weather Outlook:

Sub-tropical storm Ana:

The low pressure system off the SE US coast has acquired enough organization to be classified as a sub-tropical storm and advisories were initiated on the system at 1000pm last night. Overall Ana is lacking much deep convection near its center and drifting (1-2mph) toward the north this morning roughly 170 miles off the Carolinas. While the overall health of the system is not that great, for an early May tropical system it is holding its own this morning.

Ana is in a very weak steering flow within a blocked upper air pattern over the US. This blocking should begin to break down over the weekend allowing the system to gradually move toward the NNW and N and approach/landfall on the SC/NC coasts. There is fairly good agreement on this track reasoning in an otherwise poor steering flow.

Ana is not fully tropical in nature (hence the sub-tropical naming). Without going into great detail on the why behind the tropical versus sub-tropical classifications…the point is that the system will be approaching the coast with gusty winds and heavy rainfall over the weekend. The intensity forecast is slightly more problematic since tropical and sub-tropical system gain their strength from different sources. Ana is sitting over the warm Gulf stream waters and this could allow for more intensification if the system was more tropical in nature…however dry air continues to wrap into the center from the W and SW and this is preventing sustained convection within the inner core region. Overall only slight intensification if any is expected before Ana reaches the coast.

Note: a tropical storm warning may be required later today for portions of the SC/NC coasts.

05082015 Jeff 2 unnamed.gif (43.18 KiB) Viewed 5897 times

Next Week:
Active weather to our west and north has largely missed SE TX over the last several days, but this will change late in the weekend into much of next week. The large upper level storm system currently over CA will slide into the SW US and then into the southern plains early next week. This will push a slow moving frontal boundary into SE TX while at the same time copious moisture surges into the region from the Caribbean Sea. Numerous disturbances will begin to cross the area as early as late Sunday and mid level capping gradually erodes with cooling of the middle levels. A very wet and stormy period appears likely Monday-Wednesday of next week and possibly the entire week. Flooding rainfall appears the primary threat given PWS of 1.8 inches although the severe threat is also present. Possibly a return of our late April active weather pattern by early next week.


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[snowman65]

You can have it all....My trees are doing just fine as well as my grass....take it, please! ...lol

I'll take it. The trees are still under stress and recovering from the drought. Some of the pines are still going through cycles of bursting new needles with rain and them dropping them. There are still a lot in a slow decline cycle and are just now dying off.

Eric Berger's blog (it was either last Monday or the one before) had a writeup about the rain so far this year. Even with all the perceived wetness we are very close to normal. We just forgot what Houston climate is supposed to be like. And all this is with the help of El Niño. It's a little concerning about what lies ahead for us when this El Niño cycle is over. Enjoy the moisture and lack of water restrictions while we have it.

[niner21]

There's no way this is average.

I didn't research it much but it looks to me like April was 2 times as wet as the average. The forecast on the weather channel ap had shown 80% EVERY DAY for about 2 weeks. We have trees falling over because the ground is soooooo wet up here. There's no way we need it, the ground is saturated. They've let water out of lake Conroe 5-6 times already this year.

Like the snowman said, you can have all my rain. Enjoy.

[texoz]

The Central Texas lakes still need A LOT of water. Here in Austin we're above average for the year, but storms have been missing the area 50-200 miles northwest of here where the watersheds are for the highland lakes. Current precip forecasts look somewhat favorable for that region, but the bullseye is farther northeast.

[srainhoutx]

The latest 12Z GFS and the Weather Prediction Center Extended Range Update continues to suggest a very active weather pattern developing across our Region. Stay Tuned. Rainfall amounts could lead to future Flood Watches being hoisted.

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1157 AM EDT FRI MAY 08 2015

VALID 12Z MON MAY 11 2015 - 12Z FRI MAY 15 2015

...SUBTROPICAL STORM 'ANA' TO IMPACT THE CAROLINAS...
...LARGE RAINFALL AMOUNTS LIKELY ACROSS THE WESTERN GULF
COAST/SOUTH TEXAS...

...MODEL PREFERENCES/UNCERTAINTY ASSESSMENT...
WEST COAST--
HE 8/00Z DETERMINISTIC GUIDANCE HAS INSUFFICIENT AGREEMENT HEADING
INTO THE DAY 4-5 PERIOD. THE CHALLENGE REMAINS TO BE---THE ENTRY
POINT OF THE 500MB CIRCULATION---AND EXPECT TO MAINTAIN AN
ECENS/NAEFS/GEFS APPROACH IN A 50/30/20 BLEND RATIO UNTIL THE
TRANSFER OF PACIFIC ENERGY INLAND (EASTWARD) TO THE NORTHERN
ROCKIES/NORTHERN GREAT BASIN CAN COME IN TO BETTER FOCUS. AT THE
VERY LEAST...THE ENSEMBLES AND THEIR MEANS CAPTURE THE CLOSED
UPPER-LEVEL HIGH FEATURE (PREDOMINANT SOLUTION CLUSTER) OVER
NORTHERN ALBERTA AND A SERIES OF MID-LEVEL WAVES IN A BROAD
NORTHWESTERLY FLOW PATTERN ORIGINATING IN THE GULF OF ALASKA.

THE CENTRAL PLAINS...MIDWEST AND THE ST LAWRENCE VALLEY CYCLONE--
COULD GET AWAY WITH USING ASPECTS OF THE 8/00Z DETERMINISTIC
UKMET/ECMWF FOR DAY 3 TO DAY 4 (11/12Z TO 12/12Z) IF A DEEPER
SURFACE SOLUTION OVER QUEBEC IS PREFERRED. THIS SHOULD NOT RAISE
MANY ISSUES---AS THE MEANS DO MAINTAIN A FLATTER...WESTERLY FLOW
ALOFT OVER NEW ENGLAND---AND CARRY REMNANTS OF 'ANA' OUT TO SEA
WITHOUT MUCH FANFARE.

SOUTHERN PLAINS--
A RETURN FLOW FROM THE WESTERN GULF (A SOUTHEASTERLY UPSLOPE WIND
COMPONENT INLAND) WILL GRADUALLY BROADEN---AND COUPLED WITH AN
'OVER-RUNNING TYPE MID-LEVEL PACIFIC FLOW PATTERN---SHOULD
GENERATE A RE-OCCURRING SCENARIO FOR SLOW-MOVING DIURNAL
CONVECTION ALONG THE DECAYING COLD FRONT.

UPPER-LEVEL DISTURBANCE ALONG THE SOUTHEAST COAST ('ANA')--8/00Z
GUIDANCE WAS CONSISTENT AND STABLE REGARDING THE SYSTEM'S
'MEANDERING' PROGRESSION TOWARDS THE CAROLINAS. THE SYNOPTIC-SCALE
FORECAST PHILOSOPHY REMAINS UNCHANGED AND THE ENSEMBLE MEANS HAVE
HAD A DECENT HANDLE ON THE PATTERN FOR 3 DAYS RUNNING.
PLEASE REFER TO THE NHC FOR THE LATEST INFORMATION CONCERNING THIS
SYSTEM.

...SENSIBLE WEATHER HIGHLIGHTS...
PRECIPITATION AND COOL NORTHEAST ONSHORE FLOW INFLUENCE ALONG THE
MID-ATLANTIC COAST WILL BE THE KEY FEATURES OF THE PATTERN---IN
ASSOCIATION WITH SUB-TS 'ANA'.

WELL-ABOVE NORMAL RAINFALL IS EXPECTED FOR SOUTH AND SOUTHEAST
TEXAS AND THE LOWER MISSISSIPPI VALLEY IN ASSOCIATION WITH A
DECAYING COLD FRONT...OVER-RUNNING WESTERN GULF MOISTURE AND
SLOW-MOVING DIURNAL CONVECTION.
VOJTESAK

[srainhoutx]

The 12Z European also suggests additional shortwaves and potentially yet another closed core upper low drops into the Great Basin next week with a stationary frontal boundary draped across the Southern half of Texas. The pattern next week shows no indications of relaxing through at least Thursday into Friday...if then.

[srainhoutx]

It looks like a fairly healthy upper air disturbance is heading ENE out of Mexico. Showers and isolated stronger storms are firing across portions of S Central Texas generally headed toward SE Texas this afternoon.

[srainhoutx]

The overnight guidance continues to suggest our Region is heading toward a multi-day heavy rainfall event that could last into next weekend. The much talked about blocking pattern of a Ridge to the East and a trough to our West creates a pattern conducive for deep tropical moisture to stream N from the Western Caribbean into the Western Gulf then inland over Texas. This synoptic pattern appears stuck and should linger into at least next Saturday...possibly longer.

The very cold core upper low to our West that has been responsible for the Severe Weather Outbreak this week should eventually lift NE into the Central Plains by Monday. The Storm Prediction Center has outlined an Enhanced Risk for Severe Storms Sunday across portions of East Texas into Arkansas and a Slight Risk for Severe Storms on Monday across portions of Central and SE Texas extending NE into Louisiana and the Mississippi River Valley. What Central and SE Texas has been missing as a 'trigger' or a focal point for generating enough lift for storm development will be present Sunday well into next week. A stalling frontal boundary somewhere near or just N of the I-10 Corridor will be the culprit for an extended period of heavy rainfall. The upper ridge that eventually will turn Ana NE after making landfall along the Carolinas looks to build while the next in a series of upper lows drop SE from the Gulf of Alaska into the Great Basin allowing the very pesky upper trough to remain entrenched from Northern Mexico into the Great Plains. Embedded disturbances both from the Eastern Pacific and the Gulf of Alaska look to continue dropping into the base of the upper trough and stream ENE across Mexico into Texas next week. PW's steadily increase to near or above 2 inches which is about 2 and half Standard Deviation above normal for this time of year, appears locked in place across at least the Southern half of Texas into late next week.

Embedded disturbances are suggested by all available computer models throughout next week, but are extremely difficult to forecast beyond 6 to 12 hours in advance. The upcoming pattern will be mesoscale driven, so expect a lot of day to day changes on exactly who and where the greatest threat for heavy rainfall could occur. The overnight QPF guidance suggests a large area of 10 inch rainfall amounts with some isolated totals approaching15+ inches potential through next Friday, but has shifted both East and West the past several cycles as the guidance attempts to resolve this very complicated pattern. Strong to severe storms are possible developing across the Sierra Madre mountains of Mexico and spreading ENE from the Rio Grande Valley on into Central and SE Texas almost daily next week. It does appear that the Hill Country Lakes could see some significant replenishment during the week as both upstream flooding from very heavy rainfall late this week moves down stream and very heavy possibly training storms develop this coming week across the Region. I urge those of you that are weather savoy to advise those that may not be so weather wise to pay attention to the weather during the next several days into next week. Stay Tuned!

[srainhoutx]

Briefing from Jeff last evening:

Potentially prolonged excessive rainfall event for a large part of TX next week.

Factors will be coming together over the weekend to produce several days of excessive rainfall across a large part of TX starting on Sunday and lasting through almost all of next week. Potential for river flooding and flash flooding is increasingly possible.

A slow moving and strong upper level storm system will settle into the SW US over the weekend while a strong fetch of southeasterly winds begins to bring deep tropical moisture from the Caribbean Sea NW across the Gulf of Mexico and into TX by late Sunday. Upper level flow aloft will become increasingly SW over time allowing jet stream disturbances to ride across the region starting on Sunday and lasting all next week. Most important a slow moving/stalling front boundary will enter into the picture Monday and linger across the region much of next week interacting with the copious moisture in place and the disturbances aloft.

Expect numerous rounds of excessive rainfall starting as early as late Sunday, but most likely on Monday and lasting through all next week. Will not attempt at this point to indicate any time period for better rainfall production over another at this range. I am concerned with some of the model guidance attempting to develop a 850mb circulation over SC/C TX around Wednesday which would likely be somewhat warm core and behave like a tropical system in such a tropical air mass. Such systems in the past have produced “incredible” rainfall amounts and some of the most devastating floods in the past.

Total rainfall amounts from Sunday-next Friday will likely average 4-5 inches over much of SE/SC/C TX with isolated totals of 10-15 inches possible.

Hydro:
Grounds are already soggy over much of the state east of I-35 and several river systems are elevated from recent rainfall…especially the Brazos and Trinity. Forecasted rainfall next week along with the widespread nature on top of saturated grounds and elevated rivers is cause for concern. Such forecasted rainfall amounts on near normal flow conditions would likely result in rises to flood stage, so a very close watch on area rivers and watersheds will be needed next week.

Rainfall rates will be potentially excessive in the short term with PWS surging to 1.8 inches or greater early next week. Could easily see 2-4 inches per hour or even greater in slow moving/training convection leading to rapid flash flooding across C TX and in urban areas.

Of all the forecasted rainfall events this spring (and there have been several) this one has me the most concerned due to the stalling frontal boundary and deep tropical moisture suggesting repeat rounds of excessive rainfall.

7-Day Forecasted Rainfall Totals (QPF):

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[srainhoutx]

Morning briefing from Jeff:

Heavy Rainfall Event increasingly likely next week.

Factors, including a slow moving/stalling cool front/surface trough, deep tropical moisture from both the Pacific and Caribbean Sea, and a slow moving upper level storm system, point to a very active period of weather from late Sunday-Friday of next week.

Moisture levels greatly increase Sunday into Monday as a slow moving frontal system stalls across the region Tuesday-Thursday. Expect numerous rounds of heavy thunderstorms with excessive rainfall rates of 2-3 inches per hour or greater. Air mass will be extremely moist and capable of some really big rainfall totals in a short period of time. Threat is there for slow storm motions and cell training making the overall situation worse in the face of widespread excessive rainfall totals over the next 7 days.

Forecasted Rainfall Amounts:
Rainfall amounts Monday-Friday will likely average 4-5 inches with isolated totals of 8-10 inches possible. Current WPC rainfall forecast attached below shows a very large area of excessive rainfall over a large portion of central and SE TX. Should these rainfall totals verify over the middle Colorado River basin, significant improvement would likely occur in the long term hydrologic drought on the Highland Lakes including Lake Travis.

The highest totals will be in strong relation to cell training and this is impossible to determine much more than a few hours in advance.

There is some potential for the trough axis to morph into a closed 850mb low over central TX toward the middle of the week. Such systems in a very tropical air mass can act like a decaying tropical cyclone and take on the daily rainfall pattern of intense nocturnal rainfall events in the late evening and early morning hours near/around the low center at which time the center of any such low pressure would become critical in forecasting where the greatest rainfall would likely occur.

Hydro:
Harris County watersheds are near base flow today and will likely be near base flow at the onset of the rainfall at some point on Monday. Repeated rounds of storms will raise watershed levels over time, but the main question is how long are the breaks between rounds and does any cell training setup over Harris County. Short term rainfall rates of 2-3 inches per hour support urban street flooding and ponding and this will be possible all week.

Rivers:
Area rivers are already high from the recent rainfall especially the Brazos and Trinity and the forecasted rainfall amounts and widespread nature of the event will support significant rises on area rivers with some likely going above flood stage. Only the San Jacinto River affects Harris County however persons traveling outside of Harris County especially toward central TX should be aware of the river/flash flood threat and messaging should encourage “Turn around don’t drown” as this is the type of rainfall setup that has in the past resulted in loss of life in normally dry river bottoms in central TX and at low water crossings.

Tides:
ESE fetch has really increased overnight in response to lowering pressures over NW TX. Nearshore buoys have been running 20-25mph this morning and this has resulted in higher than expected waves along the Gulf beaches. Tides are already running about 1-1.5 feet above normal and when combined with the current lunar cycle total water levels along the Gulf beaches and in Galveston Bay are nearing 3.0 ft. Currently the Galveston North Jetty is running at 2.6ft and Morgan’s Point is 1.6ft. There has been some wave run-up on Bolivar this morning pushing water levels near the top of the beaches. For the most part tides will remain at or below the 3.0 ft mark today and Sunday. Winds will weaken as the frontal boundary approaches Monday and this should begin to slowly lower tide levels.

Forecasted Rainfall Totals (Next 7 Days):

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