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Bertha over warmer waters, should strengthen

By: Dr. Jeff Masters, 4:15 PM GMT on July 06, 2008

Tropical Storm Bertha continues west-northwestward over the open Atlantic, and has now moved over some warmer Sea Surface Temperatures (SSTs) of 26°C. Wind shear has remained about 10-15 knots, and the storm appears to be responding to these slightly more favorable conditions by generating a larger area of heavy thunderstorm activity near the center. The tops of these more vigorous thunderstorms reach higher into the atmosphere, and thus show up as colder in infrared satellite loops. This morning's QuikSCAT pass showed winds of about 50 mph north of the center. Visible satellite loops show some increased organization of Bertha's low level spiral bands, and it appears the storm is beginning to intensify. Additional data on Bertha's current state will be available Monday afternoon, when the Hurricane Hunters are scheduled to pay their first visit.


Figure 1. Oceanic heat content along Bertha's forecast track. At 8am EDT today, Bertha had just finished crossing a region of near zero heat content (black colors), but is poised to cross a region of increasing heat content over the next 120 hours. The oceanic heat content is a measure of the total amount of heat in the ocean to a depth of about 150 meters. Hurricanes stir up water from down deep due to their high winds, so a shallow layer of warm water isn't as beneficial to a hurricane as a deep one. A high heat content in excess of 80 kilojoules per square centimeter is very beneficial to rapid intensification. Bertha is not passing over anything that warm in the next five days, so only slow intensification is anticipated. Image credit: NOAA/CIRA/RAMMB.

The intensity forecast
SSTs will warm quickly to 27°C by Monday morning and 28°C Tuesday morning underneath Bertha, and shear is expected to remain moderately low, in the 10-15 knot range. This should allow Bertha to intensify into a Category 1 hurricane by Tuesday. On Wednesday, Bertha is expected to hit a branch of the subtropical jet stream that will raise shear levels to 15-20 knots. The models have been steadily weakening the trough of low pressure associated with this shear in recent runs, and it now appears that the shear will not be strong enough to weaken Bertha, although it may be able to keep Bertha from intensifying further.

The track forecast
The models are now in better agreement that Bertha will track well north of the northernmost Lesser Antilles Islands, and tropical storm conditions are not likely in the islands. Bertha should continue to the west-northwest through Thursday, when a moderately strong trough of low pressure is forecast to exit the East Coast of the U.S. This trough is expected to turn Bertha to the northwest, and there is the potential for Bertha to affect Bermuda 6-8 days from now. Climatology, and the few models that we have that run out that far--the GFS and the ECMWF--suggest that this trough will be strong enough to fully recurve Bertha so that it misses the U.S. However, long range forecasts of this nature are highly erratic in their reliability, and if this trough is not strong enough to recurve Bertha, the storm may pose a risk to the U.S. East Coast 7-10 days from now.

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 Monday morning.
Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

2001. CATfour
NHC said in there 5am "Given the weak steering currents and lack of High-Amplitude trough over the western Atlantic during the next several days...IT IS NOT GUARANTEE THAT BERTHA WILL RECURVE."
2002. h6
1996. You are the only one talking about WSW and I think you are right.
My guess is still 60W before 20N.
Destin, were you serious about the W motion commensing and to expect even a WSW motion at one point?
Post #1998 yes my whole area is that misguided. My area just got and learned how how to use that fance in door plumbing and toilet. I'm glad that I got you here to learn me.
Wow i go to sleep, get up we got a hurricane, and the high pressure is stronger and building west......wow.
Looking at the steering currents wow you right about wsw movment coming. That strong high built west to texsas.
Are the BAMM models reliable? All 3 show a curve towards the west.
Post 2001. It's not absolutely certain and guarenteed to recurve but it's a likely possibility to recurve. And my area isn't misguided I mean NC gets it's fair share of t. cyclones but the majority of the models are showing a recurvature and the NHC shows it as well. Now if something should happen and it does come for the southeast coast my "misguided" area will do what we have to do to be safe and protect life & property but as of right now JMHO I see the high weakening and Bertha being pulled up and out to maybe or maybe not effect bermuda.
Jeff? LOL...so let it be written..so shall it be done? (Old Yul Brynner fan from WAAAAAY back)
Gang im getting an ill feeling about this....this is excatly the path and setup that i hate to use the Name but, "Andrew" did.
2015. Patrap
Technical Attachment

AN OVERVIEW OF NHC PREDICTION MODELS

Bernard N. Meisner
Scientific Services Division
National Weather Service Southern Region Link
I think all models will slowly start there bend westward. Did anyone notice how large of a swath at the end of the forcast period. Tells me they have not a clue where she will end up
Keep in mind that steering map could look different in 3-4 days.
2018. Patrap

Make sure you have all your Supplies,papers and start thinking about how you Would react..if a threat comes.

Hurricane Prep. Link

Ive had that feeling for a while tampaspin
The Bamm models show a bend back to the west but if they stil show that after several or more then one run and are consistent then I'll say ok it may be a trend to watch out for and look at closely but if they are just now showing a path back to the west I need to see what they show later to be concerned and/or impressed.
Quoting 2008. medic2luv:
Are the BAMM models reliable? All 3 show a curve towards the west.


Very reliable. One of the best 3 to 5 day models out there for tropical systems.
2022. KRL
Enhanced Pic Of Bertha (click to enlarge)

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 7.2.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 07 JUL 2008 Time : 114500 UTC
Lat : 19:19:59 N Lon : 50:39:12 W

CI# /Pressure/ Vmax
4.8 / 975.1mb/ 84.8kt

Final T# Adj T# Raw T#
(3hr avg)
4.8 5.3 5.3

Latitude bias adjustment to MSLP : +1.5mb

Estimated radius of max. wind based on IR : 15 km

Center Temp : +2.1C Cloud Region Temp : -55.3C

Scene Type : EYE

Positioning Method : RING/SPIRAL COMBINATION

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

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

****************************************************

Now 85 kt according to ADT
2012 I apologize i shouldn't have gotten snippy.
like oh cares if it re curve or not whats wait in tell wed and we will sure no more on what this storm will do and if the re curve it re curve and if it dos not re curve then them ones thats been saying it will be a fish or it will re curve i fixs them some nic crows to eat how you like your crows to be cook ???
can I get a link to the bamm
2028. Patrap
UNCLASSIFIED FNMOC
Back
FNMOC WXMAP Model: NOGAPS Area: Tropical Atlantic DTG: 2008070706 Link
Destin you are also correct as the weakness is forecasted and hasn't come to pass but is trying to say whats going to happen in the future. I also, don't know everything and am still learning and am not a degree having qualified Met. but will be in 2 yrs. but that still doesn't mean i know it all.
WOW it made a new jump from 79.6kt too 84.8kt and mb went from 978mbs to 975mbs
2032. Boca
Are the SSTs at surface or 100 meters?
Thanks for the clarification DestinJeff...

The cone has shifted so many times on this storm...I know a lot of storms are like this but this storm will have us all surprised before she's dissipated...
I have not looked at everything yet but the models are all starting to shift W and South.
Ok everyone...I was a bit surprised...

TAFB T5.0/5.0 90 knots
2032. Boca 7:40 AM CDT on July 07, 2008
Are the SSTs at surface or 100 meters?


At the surface; SST = Sea Surface Temperature
this storm has been rapidly strengthing all AM from the time i got up at 3:35am my time
This is what the NHC is thinking for the intensity. They might raise it higher than this but this is likely the next advisory intensity:

...INITIAL CONDITIONS...
LATCUR = 19.4N LONCUR = 50.7W DIRCUR = 285DEG SPDCUR = 13KT
LATM12 = 18.8N LONM12 = 47.9W DIRM12 = 284DEG SPDM12 = 16KT
LATM24 = 17.7N LONM24 = 44.4W
WNDCUR = 80KT RMAXWD = 20NM WNDM12 = 55KT
CENPRS = 975MB OUTPRS = 1013MB OUTRAD = 200NM SDEPTH = D
RD34NE = 100NM RD34SE = 60NM RD34SW = 40NM RD34NW = 100NM
...INITIAL CONDITIONS...
LATCUR = 19.4N LONCUR = 50.7W DIRCUR = 285DEG SPDCUR = 13KT
LATM12 = 18.8N LONM12 = 47.9W DIRM12 = 284DEG SPDM12 = 16KT
LATM24 = 17.7N LONM24 = 44.4W
WNDCUR = 80KT RMAXWD = 20NM WNDM12 = 55KT
CENPRS = 975MB OUTPRS = 1013MB OUTRAD = 200NM SDEPTH = D
RD34NE = 100NM RD34SE = 60NM RD34SW = 40NM RD34NW = 100NM

Upgraded to 80 kts (official)
2035-Where did you find that? TIA
SHIPS model now forecasted a peak of 87 knots, with weakening after 24 hours.
2042. Patrap
er,,a new Blog is up..this ones passe guys.
2040.

Ok, I was gonna keep it a secret but here ya go...just click on the file that has 022008

Link
post #2036 I understand what SST means but if the warm water was just at the surface then how would storms strengthen & maintain so doesn't the warmth have to be at least a little bit further down then just at the surface? especially since I hear talk about if storms sit over a place too long and upwell or churn the water and it brings the cooler water up to the surface? I may be wrong but I just believed that the warm water was a little bit deeper then just at the surface.
Good morning from Jupiter...

Can't wait to read Dr. Masters' next update!
2046. Patrap
er,,MAsters has a NEW Blog...this ones das kaput.
Boca
Scroll up to Dr. Masters last blog. The Oceanic Heat Content chart goes 150 meters deep. We can see where a more westerly track will put Bertha.
EST INTENSITY 976 84 KTS
EST LOC 50.1W/19.1N
TRACKMARK
52.3W/19.3N 02L/H/B/C1
54.0W/19.6N
55.1W/19.8N
57.1W/19.7N
59.3W/19.9N 02L/H/B/C2
60.8W/20.1N
***STOP***
wow 80kt winds now its been rapidly strengthing and the nhc forcast the winds to olny be at 80kt in 36hrs well ooops
2052. Patrap
NEw BLOG..Dr. Masters Link
2053. Patrap
Are ya'll deaf?

LOL
I may be wrong but I just believed that the warm water was a little bit deeper then just at the surface.

It is, in a layer that is usually around 50 meters deep, deeper in the Caribbean, as this map of the depth of the 80*F isotherm shows:



(from http://www.aoml.noaa.gov/phod/cyclone/data/at.html)
2014. TampaSpin 12:33 PM GMT on July 07, 2008


ooooo you had to say the A WORD. I sure hope this thing isn't going to take the gutter ball track.