Tropical Summary for Friday, August, 24
Hi everyone! As a weather geek since infancy (literally -- I had a childhood phobia of thunder and lightning which created a fascination and obsession with weather!), I'm honored to have been invited to become a blogger for Weather Underground!
I will be posting a variety of types of entries, generally on the short side unless time permits for longer ones. I will also be posting tropical cyclone summaries like this one...
Image credit: NERC Satellite Receiving Station, Dundee University, Scotland
TROPICAL STORM ISAAC
- On the one hand, Isaac is still struggling to have persistent, deep, symmetric convection (thunderstorms). On the other hand, today it has become better organized: a more well-defined core has tightened up, aircraft reconnaissance has found flight-level winds that were stronger than had been present previously, and the central pressure (with which wind speed has a relationship) has dropped.
- This is occurring as Isaac approaches Hispaniola, and also an increasing amount of heavy rain is wrapping around the center to the north and northeast, and heading toward the Dominican Republic and Haiti with life-threatening urgency to the expectation of flash flooding and potential for mudslides/landslides. The storm has caused flash flooding, mudslides, downed trees and power outages in Puerto Rico yesterday and today.
- In addition to less ambiguity of where the true center of the storm is, i.e. it's not as broad and discombobulated anymore, Isaac also is making a decisive move more toward the northwest rather than west as it had been going. That, along with a steering feature evident on satellite imagery -- a trough of low pressure dipping south over the eastern Gulf of Mexico -- suggests that Isaac will move readily across Cuba to the Florida Straits and, with its large size and effects extending well in advance of the center, bring them into South Florida and the Keys beginning as early as late tomorrow night and Sunday morning.
- After Isaac enters the Gulf, the model ("European") which is normally thought to be the most accurate but had an epic FAIL with Debby has been erratic with its Isaac track forecast, shifting between a central and eastern Gulf Coast destination, whereas our other main model has been steadier and on the east side, into the Florida Panhandle and quickly. Thus there are still model differences, but regardless, the bottom line is that a tropical storm or hurricane is expected to hit the eastern or central Gulf Coast during the early-middle part of next week, and residents and visitors should stay abreast of the latest forecasts and information.
- Effects from Isaac in the U.S. will include wind, storm surge, high surf, and rainfall, and will be experienced for a longer time by people in the path of Isaac than would be the case with a storm which is tiny in size and dissipates quickly upon making landfall, such as was the case with Beryl when it hit Florida in May. Details of impacts in any given location will depend on the exact track, intensity, and structure of the storm at that time. Effects won’t be confined to the coast, and Isaac will also be capable of spawning tornadoes.
- The system which became Joyce did so briefly but just enough to tie the record for the second earliest date on which the 10th tropical storm of the season formed. It quickly met its demise and is now just a remnant low.
- Weather Underground reports that Typhoon Tembin brought 24 inches of rain in 24 hours in Hengchun, in the southern tip of Taiwan, breaking a 100-year record. Tembin is moving slowly and still rotating bands of heavy rain into southern Taiwan.
- Typhoon Bolaven is very intense -- the equivalent of a Category 4 hurricane -- and has a very large expanse of tropical storm force winds as it heads toward Okinawa this weekend.
- No tropical cyclones present or imminent, though an area of thunderstorms in the "monsoon trough" of low pressure offshore of Guatemala is being monitored.