Leslie a threat to Bermuda; Isaac is gone
Tropical Storm Leslie is struggling today under a high 20 knots of wind shear, due to strong upper-level winds out of the northwest. The high shear is keeping heavy thunderstorms confined to the southeast quadrant of the storm, as seen on satellite loops. According to the latest SHIPS model forecast, the shear is expected to stay high through Wednesday, then drop to the low category, 5 - 10 knots, on Thursday and Friday. At that time, Leslie will be over warm ocean waters of 29°C, and may intensify to a hurricane by Friday, as predicted by most of the intensity forecast models. Steering currents for Leslie are expected to collapse by mid-week, as Leslie gets stuck between two upper level lows. The storm will slowly meander over the open ocean for many days, and the latest guidance from the GFS and ECMWF models shows Leslie making a very close pass by Bermuda on Saturday, and that island can expect a 3-day period of rough weather Friday through Sunday. Leslie will stay stuck in a weak steering current environment until a strong trough of low pressure approaches the U.S. East Coast on Saturday. This trough should be strong enough to pull Leslie to the north by Sunday, September 9. At that time, Leslie may be close enough to the coast that the storm will make landfall in Canada or New England by Monday, September 10. However, making forecasts of what a tropical cyclone might do a week in advance is a sketchy proposition. Leslie could miss land entirely; this all depends upon the timing and strength of the September 8 trough of low pressure. If Leslie survives its encounter with high wind shear early this week and becomes a hurricane late in the week, the storm will bring an extended period of high waves to the U.S. coast late this week. These waves will be capable of creating dangerous rip currents and beach erosion.
Figure 1. Morning satellite image of Tropical Storm Leslie.
Invest 99L in the Central Atlantic
An extratropical low pressure system that got cut off from the jet stream and is now spinning away in the Central Atlantic near 28°N 38°W has begun to develop a small amount of heavy thunderstorm activity, and was designated Invest 99L by NHC on Sunday morning. This storm is not a threat to any land areas, and in their 8 am EDT Tropical Weather Outlook on Sunday, NHC gave 99L a 10% chance of developing into a tropical cyclone by Tuesday morning.
Isaac declared non-tropical
Hurricane Isaac's remnants are no longer considered an organized tropical system, but ex-Isaac will bring 1 - 3" of rain to Indiana, Kentucky, and Tennessee today. Isaac's remnants may bring a few tornadoes to Tennessee, Alabama, and Mississippi today, and NOAA's Storm Prediction Center has placed portions of these states in their "Slight Risk" area for severe weather. As of late Saturday night, Isaac's preliminary tornado total was 39, putting it in a tie for 12th place for most tornadoes spawned by a tropical system, according to Dr. Greg Forbes of the Weather Channel. The record holder is Hurricane Ivan of 2004, with 127 tornadoes. Isaac brought storm surges as high as 13.6' to the coast (in Lake Borgne, LA), and dumped 20" of rain at one station in New Orleans. Isaac is being blamed for at least seven deaths in the U.S., 24 in Haiti, and five in the Dominican Republic.
A few notable rainfall totals from Isaac, through Saturday:
20.08" New Orleans, LA
17.63 Wilmer, AL
17.04" Kiln, MS
16.60" Vero Beach, FL
16.29" Royal Palm Beach, FL
15.02" Marion, MS
13.99" Pascagoula, MS
13.94" Baptist, LA
13.45" Hattiesburg, MS
10.85" Gulfport, MS
10.40" Slidell, LA
10.17" Biloxi, MS
9.85" Mobile, AL
9.08" Mount Pleasant, SC
8.64" West Palm Beach, FL
8.39" Pine Bluff, AR
7.36" Charleston, SC (2.8 mi NE)
5.95" Baton Rouge, LA
5.63" Greenville, IL
Figure 2. Rainfall total for Hurricane Isaac, ending at 8 am EDT Sunday September 2, 2012. Over ten inches of rain fell in portions of Louisiana, Mississippi, Alabama, Florida, and Arkansas. Image credit: NOAA/AHPS.
I'll have a short post on Monday.
Jeff Masters
Reader Comments
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I know, I feel we aren't getting enough play about how bad it is out there. Everyone is talking about the LA area. We've got areas that are still flooded from rain that was 7 days ago. It's crazy, I've never seen it that bad here ever.
it's shear size will cause up-welling that combined with it's slow movement.
Hey Largo I saw your post and the Tampa Bay discussion may be addressing what you're seeing?
.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.
...THUNDERSTORM IMPACT...
ISOLATED THUNDERSTORMS ARE EXPECTED THE NEXT FEW DAYS. THERE IS A
LOW CHANCE FOR A FEW STRONG STORMS WITH A POTENTIAL FOR PRODUCING
SMALL HAIL AND WIND GUSTS OF 40 TO 50 MPH ACROSS INTERIOR
COUNTIES ON TUESDAY. COVERAGE OF STORMS WILL INCREASE LATE IN THE
WEEK AND INTO THE WEEKEND AS MOISTURE POOLS UP ACROSS THE STATE AHEAD OF
A WEAK COLD FRONT. THIS ACTIVITY IS EXPECTED TO BE MORE TROPICAL
IN NATURE AND NOT SEVERE.
This is from a blog Dr M done a few days ago.
Wouldn't these rain amounts account for the deficit in South and central Florida as shown on this rainfall map.
Its movement will be slow, not nearly non-existent. It's not like it will be moving at 2 mph.
While we may have a deficit of the normal amount of rain....we are by no means anywhere near a drought condition. I believe that deficit comes from us having a very dry Jan-March.
...STRONG STORMS POSSIBLE EASTERN AND INTERIOR AREAS TODAY...
.UPDATE...
AN UPPER LEVEL LOW PRESSURE SYSTEM WAS LOCATED OVER THE NORTHERN
BAHAMA ISLANDS THIS MORNING. THE UPPER LEVEL LOW WILL MOVE SLOWLY WEST
TOWARDS SOUTH FLORIDA TODAY ALLOWING FOR THE ATMOSPHERE TO BECOME
MORE UNSTABLE OVER THE EASTERN AREAS OF THE CWA. THE WESTERN AREAS
OF THE CWA WILL STILL REMAIN UNDER THE DRY AIR THAT IS SURROUNDING
THE UPPER LEVEL LOW. THEREFORE...THE POPS WILL RANGE FROM 30
PERCENT OVER THE SOUTHEAST PORTIONS OF THE CWA TO A SLIGHT 10
PERCENT OVER THE WEST COAST AND AREAS WEST OF LAKE OKEECHOBEE.
THE 12Z MIA SOUNDING IS ALSO SHOWING THAT THE MID TO UPPER LEVEL
OF THE ATMOSPHERE HAS COOLED TO AROUND -9C THIS MORNING...AND
SHOULD REMAIN AROUND -9C TODAY. THIS WILL ALLOW FOR ANY STORMS
TODAY TO BECOME STRONG WITH HAIL AND GUSTY WINDS. SO WILL CONTINUE
TO MENTION STRONG STORMS IN THE HWO MAINLY OVER THE INTERIOR AND
EAST COAST AREAS.
.DAY ONE...TODAY AND TONIGHT
THUNDERSTORMS: ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED
ACROSS THE INTERIOR AND EAST COAST METRO AREAS OF SOUTH FLORIDA
TODAY. THE MAIN IMPACT FROM THESE STORMS WILL BE LOCALLY HEAVY
RAIN, FREQUENT LIGHTNING STRIKES, GUSTY WINDS, AND HAIL.
WINDS: WIND GUSTS UP TO 50 MPH ARE POSSIBLE OVER THE THE INTERIOR
AND EAST COAST METRO AREAS TODAY WITH THE STRONGEST STORMS.
HAIL: NICKEL SIZE TO EVEN QUARTER SIZE HAIL IS ALSO POSSIBLE WITH
THE STRONGEST STORMS OVER THE INTERIOR AND EAST COAST METRO AREAS
SOUTH FLORIDA TODAY.
FLOODING: ALTHOUGH SOME AREAS HAVE IMPROVED OVER THE PAST FEW
DAYS...FLOODING CONTINUES ACROSS PORTIONS OF EAST CENTRAL PALM BEACH
COUNTY...ESPECIALLY IN LOXAHATCHEE GROVES AREA. AS A RESULT...THE
FLOOD WARNING REMAINS IN EFFECT FOR THIS AREA.
RIP CURRENTS: THERE IS A SLIGHT RISK OF RIP CURRENTS AT THE
ATLANTIC BEACHES DUE TO EASTERLY ONSHORE WINDS.
.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY
SCATTERED THUNDERSTORMS AFFECTING PRIMARILY THE INTERIOR AND EAST
CAN BE EXPECTED. THERE WILL ALSO BE AN INCREASE IN THE RISK OF RIP
CURRENTS ALONG THE WEST COAST BEACHES OF SOUTH FLORIDA THROUGH THE
WEEK.
.SPOTTER INFORMATION STATEMENT...
WIDESPREAD SPOTTER ACTIVATION IS NOT ANTICIPATED, HOWEVER
INDIVIDUAL SPOTTERS ARE ENCOURAGED TO REPORT HIGH WIND, HAIL AND
FLOODING TO THE NATIONAL WEATHER SERVICE FORECAST OFFICE IN
MIAMI.
Damn, looks like I am going to have to go buy some more tarps for the roof. There not replacing my roof for another 2 weeks.
I was noticing this last night and for 2 runs in a row the GFS shows something as well as the Euro and the Canadian.
Could be something like TS Henri in 2003:
TROPICAL WAVES...
AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 20N35W 16N35W 13N36W.
THE WAVE HAS BEEN MOVING WESTWARD 15 KNOTS DURING THE LAST 24 HOURS. SCATTERED MODERATE TO ISOLATED STRONG CONVECTIVE PRECIPITATION IS FROM 11N TO 13N BETWEEN 28W AND 33W. IT IS POSSIBLE THAT THIS PRECIPITATION MAY BE MORE RELATED TO THE MONSOON TROUGH/ITCZ. THIS WAVE LIES ON THE WEST SIDE OF A SURGE OF DEEP LAYER MOISTURE THAT IS EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY.
next aoi imo
it's moving at 8mph right now. in 1 day at it's present movement it center will travel 192miles. It's tropical wind field is 205miles, which mean's it will be in the shadow of it's previous 24hr. Wind over water for 24hrs to 36hrs will cause up-welling.
In 5 days the NHC is forecasting Leslie to travel 7, which equates to 345.55miles (1
Lat = 69.11miles)
This seems suspicious. Off Canadian coast.
Looks like about 1/3 of Isaac + some trough.
Nope. Isaac or what's left of his circulation is just NW of Louisville.
Link
It's odd how they are stacked with that N of Leslie...Meteocane stacked N over that huge blob over Africa.
North Atlantic Water Vapor Loop
Phase Diagrams (http://moe.met.fsu.edu/cyclonephase/)
especially CMC do give it some sub-tropical cyclone characteristics, and it stays over warm enough water for the next few days..
It is over KY but watch the CMC..trough comes along, splits the moisture shoving some south into the Gulf of Mexico.
Wow, that's a really cool wind map.
That pic of Presslord in a dress was 1st posted by Presslord several years ago and has been re-posted many times since.. I think it had something to do with a fund raiser for PORTLIGHT but I'm a bit hazy on that. Point is, no one was offended and it was never removed, untill today. So a big thankyou goes out to all of the blog cops and Wunder admins for being such killjoys. I speak only for myself.
So it's possible we get Michael from 99L, Nadine from the wave around 30W/11N, and maybe Oscar and Patty from those two waves over the African continent. What are your guys' thoughts?
I'm surprised the NHC didn't make a mention of that area of convection. It looks somewhat impressive.
IIRC the eastern border of the NHC's area of responsibility is 0 East/West.
The last years storm was named Rolf by the FU Berlin. Since about sixty years, highs and lows have been named by the Free University of Berlin, alternating men's names and women's names each year, 2012 the lows are female and the highs are male. (Next year it will be vice versa.)
Those names used to be common within Germany first but beginning with Lothar 1999 came to be used in other countries as well and nowadays are used through the greater part of Europa. Those names are not used in the U.K. and probably not in Norway either since in Norvay they have their own naming pattern.
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