Tropical Depression # 8 Forms…. Tropical Update 5pm Wednesday…


TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   1

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082012

500 PM EDT WED AUG 15 2012

THE LOW PRESSURE SYSTEM THAT HAS BEEN MOVING ACROSS THE EASTERN AND CENTRAL ATLANTIC OCEAN FOR THE PAST WEEK HAS FINALLY ACQUIRED ENOUGH PERSISTENT ORGANIZED CONVECTION TO BE CLASSIFIED AS A TROPICAL DEPRESSION. ALTHOUGH CLOUD TOPS ARE NOT PARTICULARLY COLD…THE CONVECTION IS DEEP ENOUGH TO MEET THE CRITERIA FOR DVORAK SATELLITE CLASSIFICATIONS…WHICH ARE T1.5/25 KT FROM TAFB AND SAB. HOWEVER…CONVECTIVE BANDING HAS IMPROVED SINCE THE 18Z CLASSIFICATIONS. ALSO…A RECENT UW-CIMSS SATELLITE INTENSITY ESTIMATE INDICATES THE INTENSITY IS NEAR 30 KT…AND THAT IS THE INTENSITY USED FOR THIS ADVISORY.

THE INITIAL MOTION ESTIMATE IS 355/16 KT BASED ON A BLEND OF VISIBLE AND MICROWAVE SATELLITE FIXES OVER THE PAST 12 HOURS. THE NHC MODEL GUIDANCE IS IN EXCELLENT AGREEMENT ON THE CYCLONE MOVING NORTHWARD AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE FOR THE NEXT 12 HOURS OR SO. AFTER THAT…A SHARP TURN TOWARD THE NORTHEAST AND EVENTUALLY TOWARD THE EAST IS EXPECTED AS THE CYCLONE BECOMES EMBEDDED IN THE DEEP-LAYER MID-LATITUDE WESTERLIES ACROSS THE NORTH ATLANTIC. BY DAYS 4 AND 5…THE CYCLONE IS FORECAST TO BECOME CAPTURED BY A SHORTWAVE TROUGH AND LIFT OUT TO THE NORTHEAST TOWARD THE AZORES ISLANDS. THE OFFICIAL TRACK FORECAST CLOSELY FOLLOWS THE CONSENSUS MODELS TVCA AND TV15.

THE DEPRESSION HAS A RELATIVELY SMALL CIRCULATION THAT IS SURROUNDED BY VERY DRY MID-LEVEL AIR. ALTHOUGH THE CYCLONE WILL REMAIN OVER FAVORABLE SEA-SURFACE TEMPERATURES FOR THE NEXT 2-3 DAYS AND IN A

LOW VERTICAL SHEAR ENVIRONMENT…OCCASIONAL INTRUSIONS OF DRY AIR ARE EXPECTED TO KEEP THE SYSTEM CONVECTIVELY CHALLENGED THROUGHOUT THE FORECAST PERIOD. ALTHOUGH NOT EXPLICITLY FORECAST…THE BEST OPPORTUNITY FOR THE CYCLONE TO ACHIEVE HURRICANE STATUS WOULD BE BETWEEN 48 AND 72 HOURS PRIOR TO THE ONSET OF STRONG WESTERLY VERTICAL WIND SHEAR ON DAY 3. THE OFFICIAL INTENSITY FORECAST IS BELOW THE MAJORITY OF THE GUIDANCE DUE TO THE POTENTIALLY NEGATIVE EFFECTS OF THE SURROUNDING DRY ENVIRONMENT…BUT ABOVE THE GFDL WHICH SHOWS LITTLE STRENGTHENING.

THIS SYSTEM IS EXPECTED TO REMAIN WELL TO THE EAST OF BERMUDA AND…THEREFORE…SHOULD NOT HAVE ANY DIRECT IMPACT ON THAT ISLAND.

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Richard Scott

WVUA Chief Meteorologist

rscott@wvuatv.com

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Active Weather Ahead… Wednesday Afternoon Forecast Update – 4:40pm

Good Wednesday afternoon to you! It’s turned out to be a mild August day across Alabama, with highs in the upper 80s across much of the area. A band of high and mid level clouds have moved into our area, and has really kept temperatures down a bit. Areas south of HWY 80 have seen more sunshine today, allowing temperatures to reach the 90s. The band of clouds over our area is in response to a weak upper air disturbance; that system will move to our south tonight. Clouds will gradually clear out tonight and on Thursday.

Thursday will remain mostly dry, with highs in the lower 90s. Expect a partly cloudy sky on Thursday, with the risk of a few storms. Most spots will remain dry on Thursday, but scattered afternoon storms are possible. Rain chance on Thursday stands at 20%. A deep upper air trough will develop and deepen over the northern US. The front will allow a cold front to move into the deep south on Friday, Saturday and Sunday. The front will become stationary somewhere across central or south Alabama over the weekend. Depending on the stall out point of the cold front will determine how much rain we get over the weekend. At this point, rain looks to be likely on Friday, with scattered to numerous storms at point on Saturday and Sunday. The best chance of rain may shift south of I-20/59 this weekend, but forecasting changes are possible, so stay with us for updates. Due to extra clouds and rain at times, highs will remain in the 80s all day on Friday, Saturday and Sunday. Rain totals may reach 3 inches in many spots between Friday morning and Sunday night. Some isolated flash flooding issues are possible.

The pattern will remain pretty active over the next couple of weeks, so rain chances will continue at times. This will help battle any mid to late summer extreme heat, so we’ll take the relatively mild summer days.

Send us your weather pictures! Send them to weather@wvuatv.com. Also, look us up on facebook and twitter. Like us on facebook by searching facebook.com/wvuaweather or WVUA-TV Weather. You can find us on twitter by searching weather@wvuatv.comor WVUA-TV Weather. Great way to get weather updates! Plus, facebook is a great way to send us weather pictures. Simply tag us!

Join us live on WVUA-TV weekdays at 4, 5, 6 and 10 pm and weekends at 10pm for the very latest on your news, weather and sports.

Richard Scott

WVUA Chief Meteorologist

rscott@wvuatv.com