A storm in the Free State on Sunday 2 October
This past week has definitely not been short of excitement weather wise, last week severe storms ripped through Oklahoma in the United States; dropping the widest ever recorded tornado, which was estimated to be a supposed conservative 3.7 kilometers wide. Unfortunately it was this tornado that also brought us our first ever storm chasing related deaths recorded in the U.S. Of the three deceased, were the infamous and veteran storm chaser Tim Samaras and his son Paul. We then saw an historic storm hit the Western Cape, bringing with it thunderstorms, hail, heavy rain and more.
Which brings us to today…
Hurricane season is now under way with Tropical Storm Andrea forming in the Gulf of Mexico overnight. There has been an area of disturbed weather which moved up from the southern Gulf of Mexico over the past few days, the area has been monitored by the NHC for a while now, with the potential for development slowly increasing, but at some point late yesterday night the storm got its act together and formed into what is now Tropical Storm Andrea, marking the first storm of the season – and right on time, just five days after the official start of the season.
Andrea finds herself in a difficult position, now located in the north eastern Gulf of Mexico, Andrea is surrounded by only marginally favourable conditions with shear and dry air being the main inhibiting factors. In fact, when looked at on water vapour imagery you can see a mass of extremely dry air to her west and south-west sides. Despite this large and extremely dry area, which is preventing her from developing convection in the SW quad, she is currently doing well with her NE and SE quads having impressive convection. The storm is moving towards the north east, heading towards the Florida coast. Due to the proximity of land, there have been recon flights into the storm already, spending the early hours of the morning inside the storm. The recon mission discovered some interesting facts, while recon was originally sent to establish whether the system had a closed circulation and could be named a tropical system, what they found later in the morning was a strengthening system. Recon reported lightning and moderate turbulence in one of the heavier bands on the northern side of the circulation too.
Dry air visible in the SW quad of Andrea
Convection visibly restricted to the E, N and NE of the storm on IR imagery.
Despite early forecasts by the NHC for the storm to remain at 45mph for the duration of its life, recon found pressures dropped down to 996hpa and that associated winds had increased to 60mph. Andrea, at the time of the 11am (South African Time) advisory – was a 60mph tropical storm, which is forecast to maintain strength until landfall tomorrow.
It looks unlikely that Andrea will manage to build convection in her SW quad, but with 60mph winds and heavy rain bands on the northern side, heavy rains, gale force winds and even tornadoes are likely for parts of Florida over the next 24 hours.
Pressure deepening visible through plotted recon data.
Below is an extract from the 11:00 advisory mentioned above:
TROPICAL STORM ANDREA DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL012013
400 AM CDT THU JUN 06 2013
SATELLITE IMAGERY AND DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER PLANE INDICATE THAT ANDREA IS STRONGER. THE PLANE REPORTED FLIGHT-LEVEL WINDS OF 63 KNOTS AT 5000 FEET AND BIAS-CORRECTED SFMR WINDS OF 49 KNOTS IN THE EASTERN QUADRANT. THE CENTRAL PRESSURES REPORTED BY THE AIRCRAFT WERE 997 MB FROM A DROP AND 996 MB EXTRAPOLATED. ON THIS BASIS…THE INITIAL INTENSITY HAS BEEN INCREASED TO 50 KNOTS. WE MUST EMPHASIZE THAT THESE STRONG WINDS ARE CONFINED TO THE EASTERN SEMICIRCLE.
ANDREA IS PROBABLY NEAR ITS PEAK INTENSITY SINCE STRONG SHEAR SHOULD HALT ANY SIGNIFICANT INTENSIFICATION BEFORE LANDFALL. ANDREA WILL INTERACT WITH AN UPPER-LEVEL TROUGH AND BEGIN TO LOSE TROPICAL CHARACTERISTICS IN ABOUT 36 HOURS…BUT TROPICAL STORM FORCE WINDS ASSOCIATED WITH THE CYCLONE ARE FORECAST TO AFFECT THE EAST COAST OF THE UNITED STATES.
FIXES FROM THE RECONNAISSANCE PLANE INDICATE THAT ANDREA IS MOVING TOWARD THE NORTH-NORTHEAST ABOUT 11 KNOTS. GIVEN THE FORECAST STEERING PATTERN PROVIDED BY GLOBAL MODELS…ANDREA SHOULD SOON BEGIN TO ACCELERATE AND TURN MORE TO THE NORTHEAST. THE OFFICIAL TRACK FORECAST IS A BLEND OF THE SLOWER ECMWF AND THE FASTER GFS MODELS.
REGARDLESS OF THE EXACT TRACK OF THE CENTER OF ANDREA…THE PRIMARY EFFECTS ARE EXPECTED TO BE HEAVY RAINFALL ACROSS MUCH OF THE FLORIDA PENINSULA AND INTO THE COASTAL SECTIONS OF THE SOUTHEASTERN UNITED STATES…STORM SURGE FLOODING ALONG PORTIONS OF THE WEST COAST OF FLORIDA…AND ISOLATED TORNADOES TODAY ACROSS THE FLORIDA PENINSULA.
FORECAST POSITIONS AND MAX WINDS
INIT 06/0900Z 27.0N 85.9W 50 KT 60 MPH
12H 06/1800Z 29.0N 84.5W 50 KT 60 MPH
24H 07/0600Z 32.0N 82.0W 40 KT 45 MPH…INLAND
36H 07/1800Z 36.0N 78.0W 40 KT 45 MPH…INLAND
48H 08/0600Z 39.0N 73.5W 40 KT 45 MPH…POST-TROP/EXTRATROP
72H 09/0600Z 46.5N 59.5W 35 KT 40 MPH…POST-TROP/EXTRATROP
96H 10/0600Z 46.5N 37.0W 35 KT 40 MPH…POST-TROP/EXTRATROP
120H 11/0600Z 52.5N 23.0W 45 KT 50 MPH…POST-TROP/EXTRATROP
To stay up to date with developments of this system, be sure to follow it in the forum: Tropical Storm Andrea Thread