Dr. Jeff Masters' WunderBlog

Bertha may pose a long-range threat to the U.S.
Posted by: Dr. Jeff Masters, 12:43 PM GMT on July 05, 2008 +6
Tropical Storm Bertha has maintained it's strength overnight, but is having trouble with Sea Surface Temperatures (SSTs) of 25°C--one degree below the threshold of 26°C considered beneficial for tropical storms. This morning's QuikSCAT pass missed Bertha, but last night's pass confirmed winds of at least 40mph. Satellite estimates of Bertha's strength have consistently put the storm's strength at 50 mph over the past day. The storm is under about 10-15 knots of wind shear.


Figure 1. Latest satellite image of Bertha.

The forecast
The models are now more confident that Bertha will not take a turn to the north east of Bermuda, with two models--the UKMET and NOGAPS--calling for the storm to pass very near the northern Lesser Antilles Islands by Tuesday night and Wednesday morning. These islands should anticipate the possibility of tropical storm conditions as early as Tuesday night, even though the current official track keeps Bertha well north of the islands. Bertha may be large enough to bring tropical storm force winds 100-200 miles from the center by Tuesday. A threat to the East Coast of the U.S. is now possible, with such an event most likely to occur about 7-10 days from now. It is also possible that high wind shear will tear apart Bertha (as predicted by the ECMWF model), or that the storm will recurve to the north just east of North Carolina, missing the U.S. The long range track of Bertha is highly uncertain, and it is too early to speculate how likely each of these scenarios is.

By Sunday morning, Bertha will be over SSTs of 26°C, which will warm to 27°C by Monday and 28°C Tuesday. this should allow Bertha to intensify to near Category 1 hurricane strength. However, by Tuesday, wind shear is expected to increase to 20 knots and remain high for several days, as Bertha encounters a branch of the subtropical jet stream. The higher shear should weaken the storm.

Elsewhere in the tropics
There are no threat areas to discuss in the tropical Atlantic, and none of the models are forecasting tropical storm formation in the next seven days.

I'll post an update by Sunday afternoon.
Jeff Masters
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2801. IKE 4:23 PM GMT on July 06, 2008    
The GFS has been showing a weaker system for a few runs...it did that last year on systems.
Member Since: June 9, 2005 Posts: 23 Comments: 37047
2802. Cavin Rawlins 4:24 PM GMT on July 06, 2008    
The only model I need is my common sense.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
2804. IKE 4:25 PM GMT on July 06, 2008    
I wouldn't put a lot into the strength it shows...it would show Dean last year at 1008 mb's when it was a strong hurricane.
Member Since: June 9, 2005 Posts: 23 Comments: 37047
2805. extreme236 4:26 PM GMT on July 06, 2008    
Well the GFS isn't an intensity model so its not worth putting much stock in to how strong it shows a system to be.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
2806. IKE 4:26 PM GMT on July 06, 2008    
2803. JFV 11:25 AM CDT on July 06, 2008
The models seriously need to get their acts together, this constant unpredictabilty from then is simply not tolerable any longer to say the least! I saw it too already IKE! where does it take it by the way?


Parks it south of Bermuda...I guess she's considering a vacation on the tax-free island.
Member Since: June 9, 2005 Posts: 23 Comments: 37047
2807. extreme236 4:27 PM GMT on July 06, 2008    
2802.

Yea and my Common Sense 12Z model run doesn't show an open wave lol
Member Since: August 2, 2007 Posts: 19 Comments: 19234
2808. rareaire 4:28 PM GMT on July 06, 2008    
im with you 0311. probably an error in Judgement but I have looked it over made an novices informed decision and I heard JIm Cantore was in Miami!! lol
Member Since: August 19, 2007 Posts: 0 Comments: 1598
2809. beell 4:29 PM GMT on July 06, 2008    
2787.
Good vid JFV,
Thanks
Member Since: September 11, 2007 Posts: 125 Comments: 12890
2810. weathersp 4:30 PM GMT on July 06, 2008    
GFS has been an outlier for a few runs.. so its either dead wrong or its right.
Member Since: January 14, 2007 Posts: 17 Comments: 4112
2811. MZV 4:30 PM GMT on July 06, 2008    
#2787 - Yes that vid from Hurricanecity was interesting. I would agree that when things get tough, the low-level flow predominates on movement. (I remember watching the upper levels of TS Chris get completely separated from the low level... which continued moving west.)
Member Since: July 3, 2008 Posts: 0 Comments: 227
2812. moonlightcowboy 4:31 PM GMT on July 06, 2008    
NEW BLOG
Member Since: July 9, 2006 Posts: 179 Comments: 28121
2813. Cavin Rawlins 4:31 PM GMT on July 06, 2008    
new blog
Member Since: July 24, 2005 Posts: 407 Comments: 19076
2815. WXHam 4:39 PM GMT on July 06, 2008    
NHC Model Composite over Google Earth. img

Member Since: July 1, 2008 Posts: 0 Comments: 33
2816. msphar 4:43 PM GMT on July 06, 2008    
Should miss the islands and Puerto Rico as it continues to climb in Latitude the next couple of days.
Member Since: August 20, 2006 Posts: 0 Comments: 258
2817. sarasotaman 4:57 PM GMT on July 06, 2008    
JFV great vid! So it backs up that the storm will stay more west than north. now with the slow down in speed we should see a near cat2 close to the Bahammas.
2818. oddspeed 8:29 PM GMT on July 06, 2008    
an interesting model

Member Since: September 4, 2007 Posts: 0 Comments: 225

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About JeffMasters
Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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