Re: May Weather Discussions. Doin' A Rain Dance!
Posted: Thu May 12, 2011 8:40 am
A day of watching the radar and the meso discussions/watch boxes march E. Morning e-mail from Jeff:
Chance for severe weather this afternoon and evening across the entire region.
Good shot at much needed rainfall.
Disturbance yesterday produced a taste of what is about to unfold in the next 12 hours across the region with many places seeing more rainfall yesterday than in the past 2 months. Next upper air disturbance is currently crossing the Rio Grande and already numerous severe thunderstorms are ongoing west of San Antonio and north of Del Rio…our activity for late today.
Local meso high pressure cell is in place this morning from short wave passage yesterday and overnight. This high will weaken and shift eastward today allowing he air mass over SE TX and the coastal bend to become very unstable. At last mid level capping has weakened due to southerly track of the approaching shot wave making the atmosphere more favorable for surface based thunderstorms. ENE moving NE Mexico disturbance will cross the region during maximum heating this afternoon favoring severe thunderstorms. Forecasted high temperatures in the upper 80’s will yield tremendous low level instability on the order of 3000-4000 J/kg while mid levels cool allowing steep lapse rates (the rate of rise of surface based air parcels) the steeper the rate the faster the surface air will rise vertically. Good inflow from the Gulf of Mexico is noted which will pump mid 70 degree dewpoint air mass into the disturbance and keep moisture profiles favorable. It all points to a good shot at rainfall.
Severe:
Cannot deny the parameters are in place for severe weather mainly wind damage and hail. 4KM WRF model continues to show the current cluster of storms growing upscale into a forward propagating MCS/large scale bow echo as it plows ESE into the mean low level flow over the region. This meso model has been showing this for the past several runs and the setup is similar to the event yesterday afternoon over N TX which resulted in a large scale bow echo and widespread wind damage. Will hit the wind threat the hardest as that is tending toward where the models are showing with their forecasted convective evolution patterns. Expect the current activity to grow upscale into a linear MCS over the next 2-4 hours and then begin to bow forward between Corpus Christi and San Antonio. Damaging wind threat will greatly increase as the leading edge begins to bow out toward the east and meso low (comma head) forms on the northern end of the complex. Cold pool generation will race eastward with the complex acting as a mini cold front and helping to sustain/maximize lift. Line/bow should reach our western counties by early to mid afternoon and sweep across the entire region from mid afternoon to mid evening. Main threat will be damaging winds of 50-70mph. Dry and brittle trees limbs will likely suffer damage even from non severe winds.
Rainfall:
Best shot at rainfall the entire area has seen and the feeling is pretty high that everyone will see at least some rainfall. Best chances will be west of I-45 where Gulf of Mexico ridge is the weakest. Will go with widespread .5-1.0 inch west of I-45 with isolated amounts up to 2.0 inches. If a fast moving bow echo develops these totals may be a touch high as the forward speed of the activity will greatly limit the duration of the event. East of I-45 totals will likely average about .5 of an inch lower.
Note: Convection yesterday W of Waco, TX was able to produce 8-10 inches of rainfall (flash flooding). There is some possibility that the main punch of the complex/bow echo may leave behind a stalling outflow boundary along US 59 or near the coast this evening. Should this happen very close attention will have to be paid to potential cell training or cell redevelopment overnight as a low level jet tries to re-establish across the region ahead of the main cold front Friday morning. Slow moving convection on any trailing outflow boundaries will be prodigious rainfall producers and could produce rapid flash flooding even with the excessively dry grounds.
Extended:
Cold front will move across the region Friday morning, but main activity and moisture should be shunted eastward with the disturbance overnight. Much drier and cooler air mass will filter into the region making for a sunny and cool (for May) weekend and early next week. Highs near 80 and lows in the upper 50’s will be a treat for this time of year.
Drought:
Yesterday marked the 58th day without rainfall at Hobby Airport…the streak should end today.
Chance for severe weather this afternoon and evening across the entire region.
Good shot at much needed rainfall.
Disturbance yesterday produced a taste of what is about to unfold in the next 12 hours across the region with many places seeing more rainfall yesterday than in the past 2 months. Next upper air disturbance is currently crossing the Rio Grande and already numerous severe thunderstorms are ongoing west of San Antonio and north of Del Rio…our activity for late today.
Local meso high pressure cell is in place this morning from short wave passage yesterday and overnight. This high will weaken and shift eastward today allowing he air mass over SE TX and the coastal bend to become very unstable. At last mid level capping has weakened due to southerly track of the approaching shot wave making the atmosphere more favorable for surface based thunderstorms. ENE moving NE Mexico disturbance will cross the region during maximum heating this afternoon favoring severe thunderstorms. Forecasted high temperatures in the upper 80’s will yield tremendous low level instability on the order of 3000-4000 J/kg while mid levels cool allowing steep lapse rates (the rate of rise of surface based air parcels) the steeper the rate the faster the surface air will rise vertically. Good inflow from the Gulf of Mexico is noted which will pump mid 70 degree dewpoint air mass into the disturbance and keep moisture profiles favorable. It all points to a good shot at rainfall.
Severe:
Cannot deny the parameters are in place for severe weather mainly wind damage and hail. 4KM WRF model continues to show the current cluster of storms growing upscale into a forward propagating MCS/large scale bow echo as it plows ESE into the mean low level flow over the region. This meso model has been showing this for the past several runs and the setup is similar to the event yesterday afternoon over N TX which resulted in a large scale bow echo and widespread wind damage. Will hit the wind threat the hardest as that is tending toward where the models are showing with their forecasted convective evolution patterns. Expect the current activity to grow upscale into a linear MCS over the next 2-4 hours and then begin to bow forward between Corpus Christi and San Antonio. Damaging wind threat will greatly increase as the leading edge begins to bow out toward the east and meso low (comma head) forms on the northern end of the complex. Cold pool generation will race eastward with the complex acting as a mini cold front and helping to sustain/maximize lift. Line/bow should reach our western counties by early to mid afternoon and sweep across the entire region from mid afternoon to mid evening. Main threat will be damaging winds of 50-70mph. Dry and brittle trees limbs will likely suffer damage even from non severe winds.
Rainfall:
Best shot at rainfall the entire area has seen and the feeling is pretty high that everyone will see at least some rainfall. Best chances will be west of I-45 where Gulf of Mexico ridge is the weakest. Will go with widespread .5-1.0 inch west of I-45 with isolated amounts up to 2.0 inches. If a fast moving bow echo develops these totals may be a touch high as the forward speed of the activity will greatly limit the duration of the event. East of I-45 totals will likely average about .5 of an inch lower.
Note: Convection yesterday W of Waco, TX was able to produce 8-10 inches of rainfall (flash flooding). There is some possibility that the main punch of the complex/bow echo may leave behind a stalling outflow boundary along US 59 or near the coast this evening. Should this happen very close attention will have to be paid to potential cell training or cell redevelopment overnight as a low level jet tries to re-establish across the region ahead of the main cold front Friday morning. Slow moving convection on any trailing outflow boundaries will be prodigious rainfall producers and could produce rapid flash flooding even with the excessively dry grounds.
Extended:
Cold front will move across the region Friday morning, but main activity and moisture should be shunted eastward with the disturbance overnight. Much drier and cooler air mass will filter into the region making for a sunny and cool (for May) weekend and early next week. Highs near 80 and lows in the upper 50’s will be a treat for this time of year.
Drought:
Yesterday marked the 58th day without rainfall at Hobby Airport…the streak should end today.