I've learned a lot about hurricanes this season. For some reason the barometric pressure isn't usually reported anymore. Millibars of central pressure are reported. At sea level pressure is 1013 millibars. Then there are "spaghetti models." I'm sure I've seen them before, but why did I only just learn the term? Probably because of watching Youtube. I used to get my hurricane knowledge from TV. Then also, there's the internet search where it's easy to check hurricane history. I learned about knots of windspeed. I've figured out how to locate projections of the hurricane path. Harvey and Irma have been remarkable and alarming hurricanes that fueled my desire to get a handle on what is going on with these hurricanes. Mostly the "news" on TV seems to be an attempt at entertainment which is very lightweight on anything I am trying to find out about the situation. If they run low on human interest stories they have started inventing them. It's great to be able to check things on the internet. "Only Hurricane Allen ... striking a relatively unpopulated area of Texas .... reached higher speeds." What a mindset. Unpopulated? It made landfall in Brownsville, Texas, population 183,000 +, sixteenth largest city in Texas.
2017 is quickly becoming a season for the record books with Harvey and now Irma.
We are quickly running out of adjectives to describe the destructive potential of Hurricane Irma. As of 2pm ET on Tuesday, the National Hurricane Center upgraded the storm's sustained winds to 185mph. This is near-record speed for a storm in the Atlantic basin, which includes the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico.
Such high, sustained winds tie Irma for the second-strongest storm on record in the Atlantic, along with Hurricane Wilma (2005), Hurricane Gilbert (1998), and the 1935 Florida Keys hurricane. Only Hurricane Allen, which reached 190 mph in 1980 before striking a relatively unpopulated area of Texas, reached a higher wind speed. Globally, the all-time record for hurricanes is held by Patricia, which reached a staggering 215 mph in the Pacific Ocean in 2015.
Although sustained winds capture the most public attention, meteorologists generally measure the intensity of a storm based upon central pressures, which are considerably lower than sea-level pressure on Earth, 1,013 millibars. Typhoon Tip, in 1979, holds this record at 870 millibars. For now, at least, Irma has a relatively high central pressure of 927 millibars. Why the storm has such an odd wind-speed-pressure relationship isn't entirely clear.
A grim forecast
Unfortunately, the forecast for Irma remains grim. The official forecast calls for Irma to bring catastrophic winds and potential storm surges to the US Virgin Islands, Puerto Rico, Dominican Republic, and the UK territory of Turks and Caicos this week. Then the forecast brings the storm to the Florida Keys as a major hurricane by late Saturday night or Sunday.
Enlarge/ Irma's ensemble model forecast from 12z run of the Global Forecast System.
Weather Bell)
There remains a fair amount of spread in the model forecasts at that point. Irma's intensity as it approaches Florida will depend considerably on whether the hurricane spends a lot of time over Cuba or if its center remains north of the island as it approaches the Straits of Florida.
What seems clear at this point is that a major wind and storm surge threat exists for Florida and the southeastern United States this weekend. While there is no certainty, clearly Irma has the potential to be a deadly and destructive hurricane. Whereas the majority of damage caused by Hurricane Harvey at the end of August was the result of inland flooding, Irma at this time has a much larger field of hurricane-force winds. Its primary threats will therefore be winds and storm surge.
No comments:
Post a Comment