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Ntxw wrote:When winter was summer, and now summer is the new winter?
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Heavy rainfall and severe weather possible over the next 48 hours.
A strong storm system currently over S AZ will swing E then ENE across the southern plains over the next 48 hours providing lift across a moisture and unstable air mass over TX. Low level southeasterly flow over the last 3 days has brought an extremely moist western Caribbean air mass into the region with surface dewpoints of 72-77 over the region and PWS of 1.8-2.0 inches. Lead short wave is starting to eject across TX currently with lift increasing along the I-35 corridor where local radars show the formation of showers and thunderstorms. Capping is still evident over SE TX and will require mid 80 degree temperatures to break…which should be attainable once the low cloud deck burns off.
Not sure really any of the short range high resolution models have a good handle on the convective development today. TX TECH WRF is way overdone so think it may be too aggressive, but the HRRR does not look all that better. Both models show significantly more development this morning than what is taking place…possibly due to the capping in place. Will favor the western and NW counties for the greatest storm chances starting later this morning and peaking this afternoon/evening. Overall meso pattern is one of favorable forced low level boundaries within a highly moist and unstable air mass supporting strong to severe thunderstorms and very heavy rainfall.
One concern is the potential for any sustained outflow boundary to become perpendicular to the decent 20kts of low level inflow this afternoon and evening which would greatly raise the flash flood threat and the severe threat. Think the best chances of this happening would be from Columbus to Huntsville, but these types of setups almost always like to attempt to drift SE into the low level Gulf feed.
Friday looks like an even better setup for severe thunderstorms and heavy rainfall, but will greatly depend on just much development and where this development occurs today. Main trough axis approaches which will help to erode the capping over the area and the upper level winds become strongly divergent supporting sustained lift. Do think it is going to take much to get storms going. Latest meso models…if they are to be believed…show both an early morning round of storms followed by a second round of slower moving storms dropping SE from NC TX during the late afternoon and evening hours. Low confidence that this is going to work out this way with the potential for any morning storm complex to stabilize the air mass.
Memorial Day Weekend:
Unlike 2015 which brought devastating flooding to TX, 2016 should be more tranquil with weak ridging attempting to develop aloft. Could still see some activity on Saturday before moisture levels drop. SW US mean upper trough position reloads by late Sunday into Monday and the next slow moving strong upper level storm system begins to head for TX early to mid next week in a pattern that has been locked in place now for the last 6 weeks.
ATL: 91L
Surface low pressure has developed over the SW ATL north of the Caribbean Sea on the tail end of an old frontal trough. 25-30kts of SW wind shear have resulted in little to no thunderstorm formation around this surface low, but conditions are expected to become increasingly favorable for development as the system drifts toward the WNW and NW this weekend allowing deep convection to build closer or over the low level center.
The National Hurricane Center currently gives the system a 70% of tropical cyclone formation over the next 5 days. Interest along the SE US coast from NC to FL should closely monitor the progress over this system. A USAF hurricane hunter mission is currently scheduled for early Friday to determine if a tropical depression or tropical storm is forming.
NOTE: effective with the 2016 hurricane season, storm surge inundation graphics will be provided by NHC with each advisory package when a tropical system is within 48 of landfall. These maps will show the reasonable worst case storm surge above ground level based on the expected forecast track of the tropical system. These maps should be available roughly 1 hour after the official advisory package is released from NHC.
4.60 inches in 1-hr at Lake Conroe Dam.
Excessive rainfall moving into Harris County as slow moving line of intense thunderstorms sags southward. Hourly rainfall rates of 3-5 inches per hour are likely with rapid onset flash flooding. 2-hr totals over 6.0 inches over SW/W Montgomery County and 3-hr totals nearing 10-12 inches over Washington and N Waller Counties.
Expect this line to progress into Harris County with similar rainfall rates and rapid onset flash flooding.
***Dangerous flash flood event ongoing over SE TX***
10-14 inches of rain has fallen this afternoon over Washington County with 6-8 inches over N Waller and southern Montgomery Counties.
Damaging flash flooding is in progress over the area with numerous roadways impacted and some homes flooding in N Waller and S Montgomery Counties.
Large MCS responsible for this is slowly sagging S while training W to E along and N of I-10. Line has become increasing fragmented in the last few hours, but cells along this line remain strong and capable of intense hourly rainfall rates of 2-4 inches. 1-hr rainfall rate of 4.6 inches was recorded in Conroe earlier this evening.
Significant flash flooding is in progress in many locations and travel should be avoided. Do NOT drive into high water.
Hydro:
Working several developing situations…especially the Brazos where rain “bomb” near Brenham will send a major flood wave down this system. Early forecast looks like Memorial Day 15 levels for Waller, Fort Bend, and Brazoria Counties, but we are not done and may need to push more water into the system.
Worried about the West Fork at Humble also with 6-8 inches over the headwaters of this basin.
Tremendous flow is going into Spring Creek and rises to overbanks is likely upstream of SH 249.
Man I hope not. Seems like all the rain has fallen elsewhere lately. I shouldn't complain, some rain has fallen the last few days. Nothing major though. The blob of beautiful rain west of here might make it.
I counted 5 100+ days, which all occurred in August over a consecutive day period. I'll take that.
. I know Larry Cosgrove is thinking hot summer but his analogs are too straightforward La Nina climo. You have to consider the 500mb weakness shown in the maps I posted in the summer thread. Over the past 90 days evidence is getting more clear of that weakness vs a 1998 or 2010 which were hot, dry Nina changes. More in li e with the 1973/2007 group