Bertha slowly intensifies, continues west-northwest

By: Dr. Jeff Masters , 12:22 PM GMT on July 04, 2008

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Tropical Storm Bertha has slowly intensified overnight, with new heavy thunderstorm activity building up around the center. Sea Surface Temperatures (SSTs) are now slightly below the threshold of 26°C considered beneficial for tropical storms, and this is limiting Bertha's intensification. This morning's 4:01am EDT QuikSCAT pass revealed top winds of about 30 mph, but the satellite was not able to reliably detect Bertha's strongest winds, since QuikSCAT does poorly in heavy rain. Bertha's current intensity is based mostly on satellite imagery of the cloud patterns. The storm is under about 10 knots of wind shear. Bertha should continue to slowly intensify today.


Figure 1. Track chart of all Atlantic tropical storms that have formed east of 40°W longitude since 1851.

The forecast
Not much has changed in the forecast, with all of the computer models foreseeing a west-northwest track into the mid-Atlantic over the next five days, with a possible recurvature to the north by the end of the period. Whether this recurvature takes place depends on how strong Bertha gets. A larger, stronger storm will be more likely to "feel" the approach of the trough of low pressure expected to recurve Bertha, which a shallower, weaker storm might be able to avoid recurvature and continue west-northwest. Wind shear is expected to remain below 10 knots the next three days, then increase to 30-40 knots by day five, according to the GFS model, when Bertha hits a branch of the Subtropical jet stream. The GFDL model does not go along with this high shear forecast, and makes Bertha a Category 2 hurricane that begins recurving to the east of Bermuda. In contrast, the HWRF model keeps Bertha a weak tropical storm for the next six days. Suffice to say, there is a lot uncertainty in the long range intensity forecast for Bertha!

The hurricane season of 2008 sets a new record
Bertha's at 25° West longitude is the farthest east a tropical storm has ever formed in the Atlantic so early in the season. Reliable records of Eastern Atlantic storms go back to 1967, the beginning of the geostationary satellite era. It's remarkable that no other early July storm even comes close to matching how far east Bertha formed (Figure 1).

Is the formation of Bertha a harbinger of an active hurricane season?
Probably. According the the Hurricane FAQ, "as shown in (Goldenberg 2000), if one looks only at the June-July Atlantic tropical storms and hurricanes occurring south of 22°N and east of 77°W (the eastern portion of the Main Development Region [MDR] for Atlantic hurricanes), there is a strong association with activity for the remainder of the year. According to the data from 1944-1999, total overall Atlantic activity for years that had a tropical storm or hurricane form in this region during JJ have been at least average and often times above average. So it could be said that a JJ storm in this region is pretty much a "sufficient" condition for a year to produce at least average activity."

Elsewhere in the tropics
A tropical wave (93L) that passed through the Lesser Antilles Islands Wednesday night is now in the central Caribbean and is very disorganized, thanks to high wind shear. This wave is not expected to develop, and no computer models are predicting development anywhere else in the Atlantic over the next seven days.

I'll post an update Saturday morning. Happy 4th of July weekend!
Jeff Masters

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238. reedzone
2:44 PM GMT on July 04, 2008
Nice update Masters, it's a tough forecast.
New Blog on Bertha with my 2nd run!
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237. weathersp
10:45 AM EDT on July 04, 2008
229. Sure thing HurricaneGeek

http://euler.atmos.colostate.edu/~vigh/guidance/

Go to North Atlantic Basin and Frame 1 will be Bertha.
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235. apocalyps
04:45 PM CEST op 04 Juli, 2008
93L is coming back.
I dont trust 93L.
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234. MrSea
2:45 PM GMT on July 04, 2008
thank you!
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232. extreme236
2:44 PM GMT on July 04, 2008
Here MrSea:

Link

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231. weathersp
10:43 AM EDT on July 04, 2008
According to DORVAK Bertha is at 51kts which is approximately 59 mph.
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230. Tazmanian
7:38 AM PDT on July 04, 2008
this is for Ex 93L

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI JUL 04 2008


TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 70W/71W S OF
18N MOVING W 15-20 KT. ADDED A WEAK 1013 MB LOW ALONG THE AXIS
NEAR 15N BASED ON A SMALL SWIRL EVIDENT ON SHORTWAVE IR IMAGES.
THIS LOW MAY BE 1-2 MB LOWER IN PRES CURRENTLY BASED ON
SURROUNDING
BUOY DATA. ASSOCIATED SCATTERED SHOWERS AND TSTMS HAVE INCREASED
THIS MORNING...NE OF THE EXPOSED LOW-LEVEL SWIRL DUE TO S-SW
SHEAR...FROM 15N-17N BETWEEN 66W-70W.
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229. HurricaneGeek
10:41 AM EDT on July 04, 2008
Hi! happy 4th of July... now america is 232 years old... that's old.

anyway, I see post 161, weathersp, if you could, could you give me a link. Thanks! =)
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228. atmoaggie
2:42 PM GMT on July 04, 2008
then that person defaults to ignore for the rest of the readership!

Awesome idea and would be very nice. Why? Then others wouldn't be quoting everything said by someone 90% have ignored. Sounds like utopia.
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227. K8eCane
2:42 PM GMT on July 04, 2008
220.
Hi breald
i was in wilmingtn in Fran
worst i can remember being in
am still in wilmington btw
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226. MrSea
2:43 PM GMT on July 04, 2008
extreme where do you find the early 12z runs?
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224. extreme236
2:41 PM GMT on July 04, 2008
HWRF seems to have increased its forecasted intensity peak to about 55 knots on the 12Z run based upon the early cycle intensity run.
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223. atmoaggie
2:38 PM GMT on July 04, 2008
only place in the world where a HUMAN Mind can beat a computer mind..

partly because the physical equations have no real solution and can only be estimated (think calculus). They all use a Taylor series carried out to some limited number of terms, then truncated...Ta-da ERROR. A slight one that grows over time.

Our human minds are capable of sifting through the results and finding a solution that meets our real world experiences and expectations.
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222. Weather456
10:41 AM AST on July 04, 2008
206. extreme236 10:38 AM AST on July 04, 2008

Not exposed but skewed. She is showing the shear pattern.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
221. MrSea
2:40 PM GMT on July 04, 2008
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220. breald
10:33 AM EDT on July 04, 2008
FranAteMyRoof, were you in North Carolina at that time? I was in Raleigh and did not expect the ddmage that was done.
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218. philliesrock
2:38 PM GMT on July 04, 2008
2 things about the 12z early models:

1. Another shift west, no model forecasting a recurve yet (except the LBAR).

2. Over 80% of the models bring Bertha to over 50 kts.
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217. K8eCane
2:39 PM GMT on July 04, 2008
206
i personally think the center is under the deepest convection and we are gonna see some strengthening today and especilly tonite
just my dumb opinion
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216. MZV
2:33 PM GMT on July 04, 2008
Interesting, StormKat is already hidden from me, and I've never clicked ignore... Maybe the blog software has some kind of threshold. If too many people put someone on "ignore", then that person defaults to ignore for the rest of the readership!
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215. extreme236
2:40 PM GMT on July 04, 2008
I'm not saying the convection is very deep but the center itself isn't exposed.
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214. chessrascal
10:39 AM EDT on July 04, 2008
Blob off of mexico:

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213. Nolehead
2:40 PM GMT on July 04, 2008
is that blob in GOM what the models was picking up yesterday...looks to be getting bigger off the mex-tex border, and could 93L make a comeback...i see that little swirl again.
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211. weathersp
10:37 AM EDT on July 04, 2008
Woo.. We have DORVAK:
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 7.2.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 04 JUL 2008 Time : 141500 UTC
Lat : 14:41:05 N Lon : 29:39:35 W

CI# /Pressure/ Vmax
3.3 / 999.3mb/ 51.0kt

Final T# Adj T# Raw T#
(3hr avg)
3.3 3.4 3.4

Latitude bias adjustment to MSLP : +2.9mb

Center Temp : -30.8C Cloud Region Temp : -44.8C

Scene Type : SHEAR (0.04^ TO DG)

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF
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209. pandorasbox
10:34 AM EDT on July 04, 2008
weathersp and other: thanks for your answers without making me like an idiot..i am new to the board, lurked for a awhile..however ..since i dont have experience in forecasting, I'll resort to staying quiet..and look for other boards..once again for those that answred my insignificant questions...thank you
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207. Weather456
10:37 AM AST on July 04, 2008
199. JFV 10:35 AM AST on July 04, 2008

Dont worry....They will change alot over the upcoming days.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
206. extreme236
2:37 PM GMT on July 04, 2008
Jp if you look at the latest 14:15UTC image the center is tucked back under some more convection again.

CIMSS ADT location:

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204. chessrascal
10:36 AM EDT on July 04, 2008
jp's right noone really knows whats gonna happen we just have to wait, see, and wishcast
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203. atmoaggie
2:34 PM GMT on July 04, 2008
Ya know, I hear folks say this all the time...models are a very good tool, and ya have to pick which one has the best handle on the pattern. I've seen folks say "Throw out the model information, you can't trust them" Well, these are some of the most rediculous things I've ever heard in meteorology. Where in the world do you think the NWS and NHC get there info from? It's up to the Met. to determine which the best information is. If you're tellin me you don't utilize ANY of the model info, then I don't expect any REAL forecast.

Exactly. Validate some other aspect of the models (such as upper level wind at radiosonde locations) and decide for yourself if the model has a credible solution. I also look for the model to initialize the TS in the correct location (a small beginning error can grow exponentially).
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202. extreme236
2:35 PM GMT on July 04, 2008
I think the GFDL is way too bullish on the intensity forecast. However, if you notice, the ICON intensity model is now on board with hurricane strength. It looks like there will be a halt in strengthening for a bit then some strengthening
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201. weathersp
10:34 AM EDT on July 04, 2008
191. StormW 10:32 AM EDT on July 04, 2008
Ya know, I hear folks say this all the time...models are a very good tool, and ya have to pick which one has the best handle on the pattern. I've seen folks say "Throw out the model information, you can't trust them" Well, these are some of the most rediculous things I've ever heard in meteorology. Where in the world do you think the NWS and NHC get there info from? It's up to the Met. to determine which the best information is. If you're tellin me you don't utilize ANY of the model info, then I don't expect any REAL forecast.

Rant over!


a. good rant
b. Weather is still one of the only place in the world where a HUMAN Mind can beat a computer mind.. and thats one of the reasons I love weather so much.

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198. extreme236
2:34 PM GMT on July 04, 2008
194.

lol I should have had him on there too, just never got around to it but while im thinking about stormkat it reminded me to do so. Stromtop was lucky number 10 on the list.
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197. Nolehead
2:29 PM GMT on July 04, 2008
is that blob in GOM what the models was picking up yesterday...looks to be getting bigger off the mex-tex border, and could 93L make a comeback...i see that little swirl again.
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196. atmoaggie
2:34 PM GMT on July 04, 2008
Look almost half of the intensity forecasts are calling for Bertha's development to stagnate (or weaken). Don't know if I trust them, though. This is a decent validation study, though. Making me decide where to look when a real threat is coming in for potential forecasts.

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195. weathersp
10:31 AM EDT on July 04, 2008
183. extreme236 10:30 AM EDT on July 04, 2008
180.
I know he can have his opinion but if you look at stormkat's statement, he says it like that is the fact and there is no way around it.

Ok...well..still..
don't poke the bear..
good idea..ignore.
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194. chessrascal
10:33 AM EDT on July 04, 2008
lol 236 iv had him on my list for a few months already lol
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192. extreme236
2:32 PM GMT on July 04, 2008
Oh well I added stormkat to ignore...oops forgot to add his other personality, stromtop to list...brb
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190. Tazmanian
7:30 AM PDT on July 04, 2008
i think will have 94L with in the next day or two
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189. chessrascal
10:31 AM EDT on July 04, 2008
Ouch! that dry air is really gonna hurt
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188. weathersp
10:30 AM EDT on July 04, 2008
179. pandorasbox 10:29 AM EDT on July 04, 2008
good morning folks..is this general thinking still that bertha will turn north, even though the a model shows otherwise?


Everything that I've seen shows that it will take a turn west in the next 6 hours or so. Remember though the higher N it goes the less chance it will impact land... Bermuda is on its own this time. lol
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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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