Irene roars into life; may become the season's first hurricane
Tropical Storm Irene roared into life this evening, transitioning from a tropical wave to a 50 mph tropical storm in just a few short hours. An Air Force hurricane hunter aircraft in the storm was finishing up its mission when it suddenly came across a region with intense thunderstorms and surface winds of 50 mph. The aircraft found that a center of circulation had barely closed off on the southwest edge of this region, though the plane found almost no winds from the west around the circulation center. The 6:10pm EDT center fix found a central pressure of 1007mb, which is quite high for the observed 50 mph winds. Dry air to the north and west is slowing development, as well as moderate wind shear of 10 - 20 knots, as analyzed by the University of Wisconsin CIMSS group. Infrared satellite loops and radar out of Martinique show the storm is poorly organized, with no evidence of spiral bands. The center of Irene is expected to cross over the Caribbean island of Dominica early Sunday morning, but the heaviest thunderstorms lie to the north of the center, and will affect Guadeloupe, Antigua, and St. Kitts and Nevis.
Figure 1. Evening satellite image of Irene.
The computer models have shifted southwards since yesterday, and now take Irene south of Puerto Rico on Monday, and along the south shore of the Dominican Republic on Tuesday. On Wednesday, Irene should pass near or over southern Haiti, Eastern Cuba, and Jamaica. On Wednesday and Thursday, the models agree that a trough of low pressure will dip down over the Eastern U.S., which is likely to turn Irene to the north. The exact timing and strength of this trough varies considerably from model to model, and will be critical in determining where and when Irene will turn to the north. We can expect that Irene will impact Central Cuba, the Bahamas, and the Florida Keys on Thursday, but it is uncertain whether Irene's turn to the north will take the storm into the Gulf of Mexico or not. Irene most reminds me of Tropical Storm Fay of 2008. Fay formed just off the coast of Puerto Rico, and was never quite able to get organized enough to become a hurricane, due to passage over Hispaniola and Cuba. Fay topped out as a strong tropical storm with 70 mph winds, and did over $500 million in damage in the U.S., mostly due to flooding rains in Florida that accumulated to over 25 inches in a few areas. Fay also dumped heavy rains on Hispaniola, triggering flooding that claimed eight lives.
Figure 2. Track of Tropical Storm Fay of 2008.
Irene will be battling dry air and moderate wind shear of 10 - 20 knots through Sunday, and it will take the storm 1 - 3 days to build up an eyewall and intensify into a hurricane. Irene is more of a threat than Tropical Storm Emily of early August was, since Irene has closed off a center farther east than Emily did and has more time to organize before encountering Hispaniola. I don't think passage over Hispaniola will destroy Irene, since it is a fairly large storm, and is likely to be a hurricane by then. However, if Irene follows the NHC forecast, it will have an extended encounter with Hispaniola and Cuba on Tuesday through Wednesday that will probably weaken the storm below hurricane force. Keep in mind that the average error for an official 5-day forecast from NHC for a developed storm is 200 - 250 miles. Irene could easily miss Florida and move up the East Coast and hit North or South Carolina, or pass through the Florida Keys and into Gulf of Mexico, ending up who knows where. Given the uncertainties, this weekend would be a good time to go over your hurricane preparedness if you live anywhere in the Caribbean, Bahamas, or U.S. coast, since Irene could well be paying you a visit as a tropical storm or hurricane sometime in the next week.
Harvey hits Belize
Tropical Storm Harvey made landfall at 2pm EDT on Saturday near Dangriga Town, Belize, as a tropical storm with 60 mph winds. Harvey continues to dump very heavy rains on northern Guatemala, Belize, and portions of Mexico's Yucatan Peninsula as the storm tracks westwards at 12 mph. Dissipation is expected Sunday as the storm pushes inland. Harvey was a small storm, and the strongest winds were confined to a short stretch of coast near where the center came ashore. Winds at Belize City, Belize on Saturday topped out at 15 mph.
Figure 3. Radar image of Harvey taken at 11:30am EDT on Saturday, August 20, 2011, a few hours before landfall in Belize. A small closed eye is visible just south of the offshore islands of Belize. Image credit: Belize National Meteorological Service.
An exceptionally active early part of hurricane season
It's been a strangely hyperactive season for weak storms in the Atlantic so far this year. Tropical Storm Irene is the 9th named storm this year, and its formation date of August 20 ties 2011 with 1936 as the 2nd earliest date for formation of the season's 9th storm. Only 2005 had an earlier date. The first eight storms this year have stayed below hurricane strength, making 2011 the first hurricane season since record keeping began in 1851 to have more than six consecutive tropical storms that did not reach hurricane strength. As I discussed in Friday's post, a major reason for this is the lack of vertical instability over the tropical Atlantic so far this year. We've had a large amount of dry, sinking air over the tropical Atlantic, and the usual amount of dry, dusty air from the Sahara, both helping to keep the atmosphere stable and stop this year's storms from intensifying into hurricanes. Hurricane activity typically ramps up big-time by August 20, with more than 80% of all the hurricanes and 65% of all the tropical storms occurring after that date. At our current pace, 2011 will become the second busiest Atlantic hurricane season on record, with 24 - 27 named storms. There are only 21 names in the list of names for a hurricane season, so we may have to break out the Greek alphabet again in late October this year, as occurred in 2005. Ironically, this was the last time the current set of names was used in the Atlantic, so 16 of this year's 21 names are repeats of 2005. I'm not too happy about seeing another hurricane season challenge the Hurricane Season of 2005 in any way, and let's hope we don't retire another five names this year, like occurred in 2005! With vertical instability much lower this year than in 2005, and that year having already seen one storm (Dennis) retired by this point in the season, I doubt that will happen, though.
Figure 2. The annual cycle of average hurricane frequency in the Atlantic. Historically, about 35% of all the tropical storms and 15% of all the hurricanes will have occurred by August 20.
Invest 98L near the Cape Verde Islands
A tropical wave near Cape Verde Islands off the coast of Africa, Invest 98L, is spreading heavy rains and strong gusty winds to those islands today. So far this morning, top sustained winds measured in the Cape Verde Islands were 23 mph at Mindelo. 98L has a long stretch of ocean to cross before it could affect any land areas. Approximately 70 - 80% of all tropical cyclones that pass this close to the Cape Verde Islands end up curving out to sea and not affecting any other land areas, according to Dr. Bob Hart's excellent historical probability of landfall charts. The latest set of long-range model runs go along with this idea, and I'd be surprised if 98L threatens any land areas.
Jeff Masters
Reader Comments
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And they are now overloaded to the east due to the initial repositioning.
I suspect we see a shift back to the west albeit just slightly.
Totally agree. Remember Ivan? When it was in the Caribbean it was suppose to hit West FL or ride up the spine. Then as it approached Jamaica the high strengthened a little bit and it shifted 200 miles west to Pensacola. As of right now, the trend has been east due to the northern shift of the center. Strength of high will be key.
Puerto Rico Update
Update from Caimito Alto, San Juan, Puerto Rico
Published: Sun, Aug 21 06:58 EDT
By Joan Santos
Good morning all,
We are now under a tropical storm warning and hurricane watch. Let's pray that the latter is just a precaution! Currently, the eye of the storm is about 341 miles away from the San Juan area and is moving toward the west at about 21 MPH. According to the National Huricane Center, the storm will continue to move west or west-northwest and motion is expected to slow. It looks as though it will intensify as it passes Puerto Rico and heads toward Hispanola.
About an hour ago, it was eerily quiet - the calm before the storm. As Irene approaches, it has become windy and very rainy with thunder in the distance. Visibility is way down as well.
The most recent rains have left many of the local roads with huge potholes while some have been partially washed away. We're hoping for the best here. In the meantime, we are prepared. We've moved our plants and patio furniture indoors and have cards and dominoes to entertain us should the cable go out.
Stay safe!
Joan
High pressure always builds in behind Low pressure. When its tropical that is warm air that is spinning counter clockwise.
14.3n55.0w, 14.6n57.0w, 15.0n59.0w, 16.0n60.4w, 16.8n62.4w are now the most recent positions
Starting 20August_12pmGMT and ending 21August_12pmGMT
The 3 eastern line-segments represent TropicalStormIrene's path
and the westernmost line-segment is the straightline projection.
Using straightline projection of the travel-speed&heading derived from the ATCF coordinates spanning the 6hours between 6amGMT then 12pmGMT :
TS.Irene's travel-speed was 24mph(38.6k/h) on a heading of 292.8degrees(WNW)
TS.Irene was headed toward passage over CanegardenBay,St.Crois ~5&2/3rdshours from now
Copy&paste ptp, 14.3n55.0w, 14.6n57.0w-15.0n59.0w, 15.0n59.0w-16.0n60.4w, 16.0n60.4w-16.8n62.4w, stx, 16.0n60.4w-17.7n64.72w, pse into the GreatCircleMapper for more info
The previous mapping (for 21August_6amGMT)
On balance a TS or low level Cat1 may weigh in on the more beneficial side vs. the harm.
indeed. i'm worried about those people that are not tech savvy and rely on local mets. disaster written all over it.
So if the storm is far enough to your East, don't count on to much interaction, especially since the East side of a storm tends to create the worst weather
I can't post it but someone already did. Maybe someone else can post it or go to my WU Blog.
24.5 and 80.5 is Islamorada, fl
Just took a look...Barilla pasta, prego pasta sauce, Luziann iced tea bags, Frosted Flakes, Red Baron Biscuit Style Scrambles...these are among the highlights!
Link
yep, yep, and yep....see you got a good sleep....:)
Latest Tracks......
but its south of that track and right or dead on with the NHC track
Link
IIRC, Ivan was also expected to travel directly across Jamaica. It wobbled a little to the west right before landfall and skirted the island.
30 miles one way or the other can really change the story in this part of the world.
That's not their job. There are PEOPLE living on those islands, and frankly those people have MUCH less ability to cope with the impact of a hurricane than people in Florida.
Let's try to cut down on wishing that a disaster will befall some of the poorest people on earth...
Models are favoring the East Coast of Florida.....and if you live in Georgia and South Carolina.....HEADS UP!
Yes but that was issued prior to the updated forecast track by the NHC being issued at 5am. that entry locations shifts about 100 plus miles east under the new track
You're following a pocket of dry air. That's not the real center.
I noticed that the models are now taking the storm over a lot of those mountains....shouldn't the storm weaken and die over hispanola? Thanks!
Andrew was also a compact storm, a larger and more developed hurricane can create effects across the entire state. Still too early to tell.
The 144h run of the NAEFS shows the split track solution in the ensembles rather well, with 1 zone of uncertainty in the surface pressure field east of FL and another in the central Gulf of Mexico. Since all the pressure fields (40 ensemble members from CMC and GFS) are averaged, the intensity of Irene gets washed out in this product. Still a tough call to make for the NHC.
Yes, for sure! The larger mountains will tear the hell out of the low level center.....but, we have seen LLC jump and reform very quickly before and reorganize very quickly in those very warm waters in the Bahamas and Keys.
No it's not.
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