Dr. Jeff Masters' WunderBlog

92L still a threat to develop; record SSTs continue in the tropical Atlantic

Posted by: Dr. Jeff Masters, 13:44 GMT le 10 septembre 2010

A tropical disturbance (92L) over the Lesser Antilles Islands lost most of its heavy thunderstorms last night, due to an infusion of dry air. However, 92L has redeveloped a moderate amount of heavy thunderstorm activity this morning, and remains a threat to the Caribbean--though not as great a threat as it appeared yesterday. Satellite loops show that 92L's heavy thunderstorms are slowly growing in areal coverage, and are becoming more organized. St. Lucia reported sustained winds of 33 mph this morning in a heavy rain squall, and heavy rain showers and gusty winds can be expected throughout the southern Lesser Antilles Islands today. Martinique radar shows that heavy rains are now affecting that island, but there is no rotation to the radar echoes evident. Surface observations indicate that pressures continue to fall at a number of stations in the Lesser Antilles, but no surface circulation is evident in the wind reports. A strong flow of upper level easterly winds is creating a moderate 10 - 20 knots of wind shear on the south side of 92L. The waters are at near-record warmth, 30°C, and these warm waters extend to great depth. Water vapor satellite loops show a large area of dry air lies over the northern Caribbean, and this dry air could interfere with development over the next few days.

Forecast for 92L
The disturbance is moving westward at 5 mph, but steering currents favor a more west-northwest motion Saturday. Lower shear lies over the Central Caribbean, away from the coast of South America, so any northward component of motion will allow for more significant development. There is drier air to the north, but 92L is steadily moistening the atmosphere in the Caribbean, so dry air may not be a problem for it. Model support for development is less than it was yesterday. The GFS and NOGAPS models do not develop 92L. The HWRF, GFDL, and UKMET models predict development, with a track taking 92L into the Dominican Republic on Sunday as Tropical Storm Julia. These models predict the storm will continue west-northwest, affecting Haiti, Eastern Cuba, Jamaica, and the Southeast Bahamas early next week. The ECMWF model foresees a more southerly track, taking 92L into Mexico's Yucatan Peninsula seven days from now.

Residents of the northern Lesser Antilles Islands and Puerto Rico should anticipate the possibility of heavy rains from 92L affecting their islands on Saturday and Sunday, though most of the action will probably stay south and west. The southern Dominican Republic should see heavy rains of 3 - 6 inches on Sunday and Monday from 92L, and Haiti, Jamaica, and eastern Cuba should anticipate similar rains on Monday and Tuesday. Should 92L make a direct hit on the Dominican Republic, it could destroy the storm, though. NHC is giving 92L a 40% chance of developing into a tropical depression by Sunday, which is a reasonable forecast. The first Air Force Hurricane Hunter mission into 92L is scheduled for Saturday morning, but there will be two research missions into the storm today that will give us valuable information on 92L's large scale environment and potential for development.

Figure 1. Morning satellite image of 92L.

Igor
Tropical Depression Igor has survived a bout with high wind shear, and is now in an environment of moderate 10 - 20 knots of shear that should allow for steady strengthening. Waters are warm, 28°C, and the Saharan Air Layer (SAL) is probably not close enough to Igor to prevent development. The models continue to predict development of Igor into a hurricane 2 - 4 days from now. Igor will track west to west-northwest over the next week, with long range forecasts from the GFS and ECMWF models putting the storm several hundred miles northeast of the Lesser Antilles Islands about 6 - 8 days from now. Climatology shows that about 10% of all tropical cyclones that have existed at Igor's current position have gone on to hit the U.S. East Coast; these odds are about 5% for Canada. The forecast steering pattern for the coming two weeks from the GFS model shows a continuation of the pattern we've seen all hurricane season, with regular strong troughs of low pressure moving off the U.S. East Coast. This pattern favors Igor eventually recurving out to sea without affecting any land areas. The odds of Igor hitting land in the U.S. or Canada are probably close to their climatological 10% and 5% probabilities, respectively.

Elsewhere in the tropics
The GFS and ECMWF models predict the development of a new tropical wave off the coast of Africa 3 - 6 days from now.

August SSTs in the tropical Atlantic set a new record
Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes had their warmest August on record, according to an analysis I did of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. SSTs in the Main Development Region (10°N to 20°N and 20°W to 80°W) were 1.23°C above average during August, beating the previous record of 1.01°C set in August 2005. August 2010 was the 7th straight record warm month in the tropical Atlantic. The five warmest months in history for the tropical Atlantic have all occurred this year; June 2005 comes in sixth place, and August 2010 in seventh. As I explained in detail in a post on record February SSTs in the Atlantic, the Arctic Oscillation (AO) and its close cousin, the North Atlantic Oscillation (NAO), are in large part to blame for the record SSTs, though global warming and Atlantic Multidecadal Oscillation (AMO) also play a role.

The Bermuda-Azores High was weaker than average during August, which drove slower than usual trade winds over the tropical Atlantic. These lower trade wind speeds stirred up less cold waters from the depths than usual, and caused less evaporational cooling than usual, allowing August SSTs to remain at record warm levels. The Bermuda-Azores High and its associated trade winds are forecast to be at near-average strength during the next two weeks, according to the latest run of the GFS model. This means that Atlantic SST anomalies will continue to stay at record warm levels during September, significantly increasing the odds of major hurricanes in the Atlantic.

Figure 2. The departure of sea surface temperature (SST) from average for September 9, 2010. Note the area of cool anomalies off the U.S. East Coast, due to the passage of Hurricane Earl. Cool anomalies are also evident east of Bermuda, due to the passage of Hurricane Danielle. Image credit: NOAA/NESDIS.

Next post
I'll have an update Saturday morning.

Jeff Masters

Categories: Hurricane

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601. Jedkins01 18:42 GMT le 10 septembre 2010
Remember guys, the only model that can give an accurate forecast for Igor is the EURO :) Member Since: 21 août 2008 Posts: 0 Comments: 5336

605. wayfaringstranger 18:44 GMT le 10 septembre 2010
Quoting sporteguy03: He is is an excellent resource and does not get paid to answer on the blog at least from my understanding, he has offered to allow people to see his forecasting planning in Palm Harbor, he is on the Barometer Bob show frequently answering questions. I could not dedicate the time he has to this blog to do the same. Can a blogger contact a person of his knowledge and get as fast a reply as Stormw does? Top few things on this blog: StormW's analysis Reed, Levi, Drak's analysis The ignore user button (the new poof) Destin J's avatars..... and of course the super dooper ECMWF squared model. Member Since: 12 juillet 2010 Posts: 0 Comments: 235

607. angiest 18:44 GMT le 10 septembre 2010
Quoting StormW: Correct...the NAO in it's negative phase so far, has been doing as I've found in research...if you have noticed the ridge has been 'bridging", and the trof in the center has been basically displaced a little further north. The trofs coming of have been anomalously strong, at least in my book. They look like something for October and on...not Aug and Sep. But as I've bolded that portion of your statement, that is how the negative setup essentially works. Thanks! Member Since: 26 août 2006 Posts: 16 Comments: 4766

608. RyanFSU 18:45 GMT le 10 septembre 2010
ECMWF 12z takes Igor on a hard right turn NNW... (forecast thru 168hrs) Member Since: 13 février 2005 Posts: 0 Comments: 308

609. Drakoen 18:45 GMT le 10 septembre 2010
Quoting Jedkins01: Remember guys, the only model that can give an accurate forecast for Igor is the EURO :) What year are you at FSU? Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

613. Jax82 18:47 GMT le 10 septembre 2010
I think we all know how accurate 5-7 day model forecasts are. Not very accurate. If I remember correctly with Earl we hardly knew when he would that NE curve and he was right off the east coast. Trying to figure out if Igor will hit the US when its 10 days away will just drive you crazy! Member Since: 2 septembre 2008 Posts: 1 Comments: 1261

615. CosmicEvents 18:47 GMT le 10 septembre 2010
Quoting Ryuujin: Amen. What I don't understand is how some bloggers on here constantly get by with simply posting models and data that only support their position, and when any model or any forecaster posts anything contrary they simply ignore it. This shouldn't about being one up on your fellow bloggers, but about trying to provide the best possible anaylsis of a situation and why you feel something will happen. The "I'm better than you" attitude of some of the bloggers here sickens me I agree. The more info the better and let the reader decide what they like best. Personally, for me it's not even close. After I read the NHC discussion I click on Weatherguy03 and watch his daily video blog. Or twice or 3 times a day if needed. Nicely presented so even people with no knowledge can understand. I've been recommending his blog for years and I've never had anyone say anything other than "thank you" after viewing them. Cuts to the chase, and in 10 minutes or less you're current with what's going on. Plus, fwiw, he remains the only trained met that's ever graced these blogs with his free analysis. And he's got a pleasant calming way of presenting the situation. No grouchies here. Member Since: 3 août 2005 Posts: 10 Comments: 5099

617. IKE 18:47 GMT le 10 septembre 2010
ECMWF on day 8.....Link Member Since: 9 juin 2005 Posts: 23 Comments: 37044

618. Drakoen 18:48 GMT le 10 septembre 2010
Quoting Jedkins01: Freshman Same here Member Since: 28 octobre 2006 Posts: 57 Comments: 29010

621. NASA101 18:49 GMT le 10 septembre 2010
Quoting help4u: ECWMF TAKES IT STRAIGHT NORTH,bye bye Igor!!!!!!!!!! People on here are paying too much attention on a particular run! Lots of uncertainty out there for IGOR - we DO NOT yet have model consensus!!!! Member Since: 16 août 2007 Posts: 0 Comments: 276

623. NASA101 18:50 GMT le 10 septembre 2010
People on here are paying too much attention on a particular run! Lots of uncertainty out there for IGOR - we DO NOT yet have model consensus!!!! Member Since: 16 août 2007 Posts: 0 Comments: 276

624. SLU 18:50 GMT le 10 septembre 2010
374 WHXX01 KWBC 101848 CHGHUR TROPICAL CYCLONE GUIDANCE MESSAGE NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1848 UTC FRI SEP 10 2010 DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS. PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE AND SUBTROPICAL CYCLONE INFORMATION. ATLANTIC OBJECTIVE AIDS FOR DISTURBANCE INVEST (AL922010) 20100910 1800 UTC ...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS... 100910 1800 100911 0600 100911 1800 100912 0600 LAT LON LAT LON LAT LON LAT LON BAMS 13.2N 60.4W 13.9N 62.0W 14.7N 63.7W 15.2N 65.5W BAMD 13.2N 60.4W 13.9N 62.2W 14.7N 64.1W 15.4N 66.0W BAMM 13.2N 60.4W 13.8N 62.2W 14.5N 64.3W 15.0N 66.4W LBAR 13.2N 60.4W 13.7N 61.8W 14.6N 63.6W 15.5N 65.6W SHIP 25KTS 29KTS 36KTS 46KTS DSHP 25KTS 29KTS 36KTS 46KTS ...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS... 100912 1800 100913 1800 100914 1800 100915 1800 LAT LON LAT LON LAT LON LAT LON BAMS 15.8N 67.5W 16.7N 71.5W 17.4N 76.0W 17.9N 80.8W BAMD 16.2N 67.9W 17.7N 71.6W 19.4N 74.9W 20.2N 77.6W BAMM 15.6N 68.6W 16.6N 73.2W 17.5N 78.1W 18.4N 83.7W LBAR 16.3N 67.8W 18.1N 72.2W 20.6N 75.7W 22.7N 78.0W SHIP 59KTS 74KTS 82KTS 99KTS DSHP 59KTS 74KTS 82KTS 99KTS ...INITIAL CONDITIONS... LATCUR = 13.2N LONCUR = 60.4W DIRCUR = 300DEG SPDCUR = 5KT LATM12 = 12.7N LONM12 = 59.6W DIRM12 = 297DEG SPDM12 = 5KT LATM24 = 12.2N LONM24 = 58.3W WNDCUR = 25KT RMAXWD = 50NM WNDM12 = 25KT CENPRS = 1009MB OUTPRS = 1010MB OUTRAD = 120NM SDEPTH = S RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM $$ NNNN Member Since: 13 juillet 2006 Posts: 11 Comments: 2851

625. SLU 18:50 GMT le 10 septembre 2010
374 WHXX01 KWBC 101848 CHGHUR TROPICAL CYCLONE GUIDANCE MESSAGE NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1848 UTC FRI SEP 10 2010 DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS. PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE AND SUBTROPICAL CYCLONE INFORMATION. ATLANTIC OBJECTIVE AIDS FOR DISTURBANCE INVEST (AL922010) 20100910 1800 UTC ...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS... 100910 1800 100911 0600 100911 1800 100912 0600 LAT LON LAT LON LAT LON LAT LON BAMS 13.2N 60.4W 13.9N 62.0W 14.7N 63.7W 15.2N 65.5W BAMD 13.2N 60.4W 13.9N 62.2W 14.7N 64.1W 15.4N 66.0W BAMM 13.2N 60.4W 13.8N 62.2W 14.5N 64.3W 15.0N 66.4W LBAR 13.2N 60.4W 13.7N 61.8W 14.6N 63.6W 15.5N 65.6W SHIP 25KTS 29KTS 36KTS 46KTS DSHP 25KTS 29KTS 36KTS 46KTS ...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS... 100912 1800 100913 1800 100914 1800 100915 1800 LAT LON LAT LON LAT LON LAT LON BAMS 15.8N 67.5W 16.7N 71.5W 17.4N 76.0W 17.9N 80.8W BAMD 16.2N 67.9W 17.7N 71.6W 19.4N 74.9W 20.2N 77.6W BAMM 15.6N 68.6W 16.6N 73.2W 17.5N 78.1W 18.4N 83.7W LBAR 16.3N 67.8W 18.1N 72.2W 20.6N 75.7W 22.7N 78.0W SHIP 59KTS 74KTS 82KTS 99KTS DSHP 59KTS 74KTS 82KTS 99KTS ...INITIAL CONDITIONS... LATCUR = 13.2N LONCUR = 60.4W DIRCUR = 300DEG SPDCUR = 5KT LATM12 = 12.7N LONM12 = 59.6W DIRM12 = 297DEG SPDM12 = 5KT LATM24 = 12.2N LONM24 = 58.3W WNDCUR = 25KT RMAXWD = 50NM WNDM12 = 25KT CENPRS = 1009MB OUTPRS = 1010MB OUTRAD = 120NM SDEPTH = S RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM $$ NNNN Member Since: 13 juillet 2006 Posts: 11 Comments: 2851

626. Cotillion 18:50 GMT le 10 septembre 2010
The ECMWF building. 'case anyone wants to add it to the shrine. (The most perplexing thing is that it's based in Reading. Of all places?) Member Since: 23 août 2008 Posts: 7 Comments: 5300

630. help4u 18:52 GMT le 10 septembre 2010
Igor heading toward positive NAO.Lesson learned. Member Since: 18 septembre 2006 Posts: 0 Comments: 1072

632. IKE 18:52 GMT le 10 septembre 2010
Day 9 ECMWF...Link Member Since: 9 juin 2005 Posts: 23 Comments: 37044

634. help4u 18:53 GMT le 10 septembre 2010
No i do hurricane relief work. Member Since: 18 septembre 2006 Posts: 0 Comments: 1072

638. JNCali 18:54 GMT le 10 septembre 2010
I can't help but wonder.... How is it possible to accurately determine the mean temperature worldwide at any given time, presently, let alone historically? When I look at the different worldwide maps showing the different climate related variables I always wonder if they in fact always average out throughout the area spanning the surface of the earth to the upper atmosphere... Member Since: 9 septembre 2010 Posts: 5 Comments: 1032

641. TheDawnAwakening 18:55 GMT le 10 septembre 2010
Quoting txag91met: -NAO and hurricanes recurving is probably not a 1 to 1 ratio. I agree, but it is pretty close. Member Since: 21 octobre 2008 Posts: 215 Comments: 3159

643. Stormchaser2007 18:56 GMT le 10 septembre 2010
SHIPS takes 92L up to 99 knots. Member Since: 9 juin 2007 Posts: 4 Comments: 15248

649. CosmicEvents 18:57 GMT le 10 septembre 2010
Quoting StormW: No grouchiness here either. You're kinda wearing out Bobs blog anyway...people can get the same on mine as well, with a better explanation. Maybe you can explain why he doesn't explain the upcoming change like I have, or go into things like the difference between the NAO phases, or the MJO Index? I don't think I'm wearing it out. Many don't know about it as he's not here to promote it due to his day job. You'd really have to ask him about the NAO and MJO stuff. It's my understanding, and my understanding only, that he feels that science is valid but we really haven't seen any strong correlations yet in that area to forecast quantity or track. But again, this is a question for expert to expert. Ask him. Member Since: 3 août 2005 Posts: 10 Comments: 5099

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