Cloud Stalker: from the Sert homepage

Wednesday, August 15, 2007

from the Sert homepage

Wednesday, August 15, 2007

Tropical Storm Dean Strengthens As It Continues Westward…Tropical Storm Erin Forms in Western Gulf…No Threat to Florida…Heat Advisory in Effect Again Today for Western Panhandle…Triple-Digit Heat Indices Continue Statewide…Scattered Afternoon Showers and Thunderstorms Expected…

At 11 AM EDT Wednesday, Tropical Storm Dean was located about 1050 miles east of the Lesser Antilles, or about 2400 miles southeast of the southern Florida coast. Movement is quickly toward the west at 20 mph. Maximum sustained winds have increased to near 60 mph, and Dean could become a hurricane by tomorrow as it moves further west into an area of weaker wind shear and increasingly warmer waters. An aircraft is scheduled to investigate Dean on Thursday afternoon. The current forecast from the National Hurricane Center keeps this system moving toward the west or west-northwest, bringing the storm across the Lesser Antilles by Friday as a Category 1 hurricane and into the eastern Caribbean Sea this weekend. Please note that there are significant uncertainties regarding long-range track and intensity forecasts for tropical cyclones. At the moment, this storm poses no threat to Florida, but it will be closely monitored.
In the western Gulf of Mexico, Tropical Depression 5 was upgraded this morning to Tropical Storm Erin. At 11 AM EDT Wednesday, Tropical Storm Erin was located about 250 miles east of Brownsville, Texas. Erin is a minimal tropical storm, with maximum sustained winds at around 40 mph. Movement is toward the west-northwest near 12 mph. A strong ridge of high pressure over the southern Plains will steer Erin toward the west, bringing the storm onto the south Texas coast sometime Thursday. This storm will have no impact upon Florida.

Meanwhile, high pressure will remain anchored over the southern Plains, keeping conditions sweltering across the state, particularly in the western panhandle, where dangerous heat and humidity is likely once again. A Heat Advisory is in effect through 7 PM CDT this evening for Escambia, Santa Rosa, and Okaloosa counties as heat indices there could climb as high as 113 degrees. Although slightly lower humidity levels and heat indices are expected over the remainder of Florida, it will still be hot, with temperatures in the mid to upper 90’s and heat indices of 100-108 degrees. Heat indices will reach the 100 degree mark before noon over many areas, falling below triple digits around 7 or 8 PM. Although no heat-related advisories are in effect for the remainder of the state, excessive heat safety should still be practiced.

If you must be outdoors, take precautions to avoid heat-related illnesses such as heat cramps, heat exhaustion, or heat stroke. Drink plenty of water, take frequent breaks, and check on the elderly as well as pets. Click here for more information and safety tips on excessive heat.

Isolated to widely scattered sea breeze-triggered showers and thunderstorms will be possible this afternoon, mainly over South Florida due to more low-level moisture. No widespread severe weather is expected, but any thunderstorms that happen to develop could become quite strong. Deadly cloud-to-ground lightning strikes, brief gusty winds, and locally heavy rain will be the main threats. Thunderstorm activity will subside after sunset.

Hurricane Local Statement forTropical Storm ERIN issued from Houston / Galveston, TX
Issued at 535 PM CDT WED AUG 15 2007

Atlantic Tropical Weather Outlook
000 ABNT20 KNHC 152102 TWOAT TROPICAL WEATHER OUTLOOK NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 530 PM EDT WED AUG 15 2007 FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO... THE NATIONAL HURRICANE IS ISSUING ADVISORIES ON TROPICAL STORM ERIN...LOCATED ABOUT 195 MILES EAST OF BROWNSVILLE TEXAS...AND IS ISSUING ADVISORIES ON TROPICAL STORM DEAN...LOCATED ABOUT 910 MILES EAST OF THE LESSER ANTILLES. ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS. PUBLIC ADVISORIES ON TROPICAL STORM ERIN ARE ISSUED UNDER WMO HEADER WTNT35 AND UNDER AWIPS HEADER MIATCPAT5. FORECAST/ADVISORIES ARE ISSUED UNDER WMO HEADER WTNT25 AND UNDER AWIPS HEADER MIATCMAT5. $$ FORECASTER LANDSEA/BROWN

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HAIL (3/4 inch or greater)

Hail can cause significant damage to your vehicle, break windows and damage roofs of homes and businesses.
Hail can cause significant bodily injuries such as broken bones and even blindness if wind blown.
Softball (4.5 inches) sized hail was reported in Lake Wales, Florida on March 30, 1996.
Haildrifts, up to four feet deep of dime to nickel sized hail, occurred in low-lying areas near Zephyrhills, Florida on January 29, 1997.
Hailstones the size of softballs can fall at speeds faster than 100 mph

supercell

Supercells derive their rotation through tilting of horizontal vorticity (an invisible horizontal vortex) caused by wind shear. Strong updrafts lift the air turning about a horizontal axis and cause this air to turn about a vertical axis. This forms the deep rotating updraft, the mesocyclone.
A cap or capping inversion is usually required to form a downdraft of sufficient strength. The cap puts an inverted (warm-above-cold) layer above a normal (cold-above-warm) boundary layer, and by preventing warm surface air from sinking too far, allows one or both of the following:
Air below the cap warms and/or becomes more moist
Air above the cap cools
This creates a warmer, moister layer below a cooler layer, which is increasingly unstable (because warm air is less dense and tends to rise). When the cap weakens or moves, explosive development follows.
In North America, supercells usually show up on Doppler radar as starting at a point or hook shape on the southwestern side, fanning out to the northeast. The heaviest precipitation is usually on the southwest side, ending abruptly short of the rain-free updraft base or main updraft (not visible to radar). The rear flank downdraft, or RFD, carries precipitation counterclockwise around the north and northwest side of the updraft base, producing a "hook echo" that indicates the presence of a mesocyclone.