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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988. kmanislander
9:54 PM GMT on July 04, 2008
Puerto Cabezas, Nic, 1010.8 mb and falling

Wind from the N @ 5mph
Member Since: August 19, 2006 Posts: 0 Comments: 15982
987. kmanislander
9:49 PM GMT on July 04, 2008
The other interesting point is that the blow up continues during the heat of the day !

It will be interesting if we start to see the "charcoal grays" in the AVN images tonight
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986. cantoriesnumber1fan
9:49 PM GMT on July 04, 2008
Impressive convection could spell trouble in the NW Carribean.
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985. northtxhurricane
9:48 PM GMT on July 04, 2008
AI. It won't pull an Humberto but it may very well pulled a Cindy...Cindy happened in early July, with similar relaxing-shear conditions if I can remember correctly.
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984. weathersp
5:47 PM EDT on July 04, 2008
Wow.. Huge convection spin just before sunset.. Its getting stronger.

Link
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983. northtxhurricane
9:43 PM GMT on July 04, 2008
TD 3 and then Cris will form in the NW Caribbean out of this disurbed weather once the SFC low comes to the area in the W Caribbean as shear lowers with the upper-level high moving on in out of the EPAC. Might even become Cindy's younger brother in terms of track and intensity. Wait and see at this point. Really the only thing to watch in the tropics right now as it is fairly close to home.
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982. weathersp
5:45 PM EDT on July 04, 2008
976. jphurricane2006 5:42 PM EDT on July 04, 2008
um sp lows can form, he said next week not next hour lol

also if that vortex from 93L moves under it, who knows


a. This is not gonna pull a Humberto...too early.

b. Yes thats true. Exept 93L is gonna have to move over the yucatan.

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981. beell
9:19 PM GMT on July 04, 2008
Happy Fourth Folks,
Not ready to defend the HWRF yet with its early turn but the ULL looks better-with a little dig to the south and what looks like an attempt to work lower down towards the surface.
SSD NW ATL Visible Loop
SSD NW ATL Water Vapor Loop
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980. kmanislander
9:42 PM GMT on July 04, 2008
Hi Keeper

Left the computer for a while. All is well here save for that shield of rain coming up from the South. Someone asked if the remnants of 93L could combine with the convection off the coast of Nicaragua and the answer is absolutely yes. In fact, Arthur was the product of the remnants of the EPAC system that came up and merged with convection in the Gulf of Honduras.

Picture it this way. The remnant low has no convection and the heavy convection has no low ( that we know of ). Seems like a likely match no ? LOL
Member Since: August 19, 2006 Posts: 0 Comments: 15982
979. bballerf50
9:44 PM GMT on July 04, 2008
Is it just me or is bertha going through more than just the dimin?
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977. KYhomeboy
9:40 PM GMT on July 04, 2008
Persistent convection from a disturbance such as the one which looks like it is developing in the caribbean can create at first...and area of broad low pressure...and once that is persistent enough a cyclone can form. This may be just a flare of convection but it must be watched as it isn't in a particularly hostile environment at present and if the convection can maintain itself....we may have issues. It doesn't have to wait until remnants of 93L creep under it to help start something in that vacinity
975. northtxhurricane
9:41 PM GMT on July 04, 2008
With the Upper Level High moving into the area, combined with the remnant surface low of 93L and the MJO phase...we will get a tropical storm out of this for sure.
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974. cajunkid
4:39 PM CDT on July 04, 2008
GOM looks interesting but the buoys are about normal...who knows though
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973. weathersp
5:38 PM EDT on July 04, 2008
969. northtxhurricane 5:38 PM EDT on July 04, 2008
I still think we will have Christobal in the NW Caribbean/GOM sometime early next week out of all this. Do not think we will get nothing out of all this convection/MJO phase.


I disagree with you here... there is NO central area of low pressure associated with that "blob" of convection. Clouds does not nessarally mean Tropical Storms.

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972. sporteguy03
9:36 PM GMT on July 04, 2008
hurricane23,
Are you still feeling the fishy track today?
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971. naplesdreamer28
5:31 PM EDT on July 04, 2008
so are we in for it in florida or what?
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970. hurricanejam
9:38 PM GMT on July 04, 2008
CIMSS/NESDIS-USAF/NRL AMSU TC Intensity Estimation:
TROPICAL STORM BERTHA
Friday 04jul08 Time: 1838 UTC
Latitude: 15.39 Longitude: -30.98
Storm position corresponds to AMSU-A FOV 13 [130]
-----------------------------------------------------------------
| Estimated MSLP: 1001 hPa
| Estimated Maximum Sustained Wind: 48 kts
| Estimate Confidence: Good ( +/- 5mb +/- 7 kts )
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969. northtxhurricane
9:35 PM GMT on July 04, 2008
I still think we will have Christobal in the NW Caribbean/GOM sometime early next week out of all this. Do not think we will get nothing out of all this convection/MJO phase.
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968. KEEPEROFTHEGATE (Mod)
9:32 PM GMT on July 04, 2008
it should have already die off jlpr in fact the early convection is or has died with new popin to replace it things are happening fast and iam checking bouys in area to confirm any pressure drops
Member Since: July 15, 2006 Posts: 192 Comments: 59074
966. druseljic
9:32 PM GMT on July 04, 2008
Very interesting and informative graphic hurricane! Thanks!
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965. hurricane23
5:28 PM EDT on July 04, 2008
CLICK HERE to view the westward trend.
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964. OUSHAWN
9:26 PM GMT on July 04, 2008
I'm keeping a very close eye on the southern BOC right now. Still looks like there is a spin in that little blow up of convection down there when I look at the visibles. Considering that is the area that a couple of the models were suspicious of yesterday it has caught my attention.
Member Since: September 20, 2007 Posts: 0 Comments: 44
963. Thundercloud01221991
9:27 PM GMT on July 04, 2008
where did everyone go I am assuming the grill???
Member Since: August 1, 2006 Posts: 28 Comments: 3716
959. hurricane23
5:19 PM EDT on July 04, 2008
Do not like the slight bend back to the left on the 5:00pm track.The trend continues.
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958. Levi32
1:17 PM AKDT on July 04, 2008
Ok right now the convection in the western Caribbean is nothing but just that, convection, due to the MJO pulse. If 93L's remnant low gets under the upper-level anticyclone in the western Caribbean then we will have to keep an eye on it as it moves into the GOM. The convection near Nicaragua will most likely die before 93L gets there, but being under that high will mean we have to keep an eye on it.
Member Since: November 24, 2005 Posts: 635 Comments: 26754
957. JLPR
9:16 PM GMT on July 04, 2008
it sure does keeper
lets hope all the convection dies tonight =) With high TCHP in the region it may explode easily but wind shear is till rather high in the area =P
Member Since: September 4, 2007 Posts: 36 Comments: 5223
956. Huracaneer
9:17 PM GMT on July 04, 2008
I noticed that the buoys near that blob by Nicaragua are starting to drop see here and here. This range of pressure drops seem fairly drastic to me. I think something is starting to develop.
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955. bballerf50
9:11 PM GMT on July 04, 2008
Is it really possible for 93L to slide under the new convection in the NW car and create a combined disturbance?
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954. 7544
9:15 PM GMT on July 04, 2008
if the blob does become 94l where will it head tia
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953. KEEPEROFTHEGATE (Mod)
9:13 PM GMT on July 04, 2008
post 937 jlpr
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952. KEEPEROFTHEGATE (Mod)
9:11 PM GMT on July 04, 2008
kman hows it going got my eyes peeled watchin blob ssw of ya things could happen real fast if it catches the right conditions at the right time
Member Since: July 15, 2006 Posts: 192 Comments: 59074
951. JLPR
9:11 PM GMT on July 04, 2008
umm that would be very interesting maybe 93L's circulation in combination with the convection in the Western Caribbean could become 94L?
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950. KEEPEROFTHEGATE (Mod)
9:09 PM GMT on July 04, 2008
kman keep a close eye if it happens to catch it will be fast
Member Since: July 15, 2006 Posts: 192 Comments: 59074
949. MississippiWx
9:11 PM GMT on July 04, 2008
946. kmanislander 9:07 PM GMT on July 04, 2008

Was just about to say that! The merger could possibly start up a stronger low pressure center. Interesting stuff indeed!
Member Since: July 15, 2006 Posts: 17 Comments: 10285
947. Levi32
9:07 PM GMT on July 04, 2008
Former 93L's circulation has become completely detached from the convection due to shear, and by tomorrow will be in the NW Caribbean in a more favorable area for development as the upper-level anticyclone moves into the area.
Member Since: November 24, 2005 Posts: 635 Comments: 26754
946. kmanislander
9:07 PM GMT on July 04, 2008
The surface low remnant from 93L is about to go underneath the high in the W Caribbean and merge with the blow up East of Nicaragua



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945. MississippiWx
9:06 PM GMT on July 04, 2008
Someone should check out the upper level analysis maps in the Western Caribbean. According to the NOAA satellite, there appears to be a small upper level high over that area of deep convection.
Member Since: July 15, 2006 Posts: 17 Comments: 10285
944. 7544
9:06 PM GMT on July 04, 2008
941. JLPR 9:04 PM GMT on July 04, 2008
whoaa lol I opened the wide Atlantic view and I was very surprised by that blob close to Central America =O it looks better than Bertha lol =P


seems to be drifting northward too
Member Since: May 6, 2007 Posts: 0 Comments: 6884
943. jscs
9:06 PM GMT on July 04, 2008
Relax...
THE NEW INTENSITY FORECAST IS UNCHANGED FROM THE
PREVIOUS ADVISORY AND KEEPS BERTHA'S INTENSITY BELOW HURRICANE
STRENGTH. THE GFDL CONTINUES TO SHOW BERTHA REACHING HURRICANE
STATUS...BUT THE SHIPS MODEL HAS BACKED OFF A LITTLE...AND IS IN
LINE WITH THE OFFICIAL FORECAST.
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942. surfmom
9:05 PM GMT on July 04, 2008
Gulf looks like a pot of hurricane soup..just waiting for the next ingredient or two
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941. JLPR
9:04 PM GMT on July 04, 2008
whoaa lol I opened the wide Atlantic view and I was very surprised by that blob close to Central America =O it looks better than Bertha lol =P
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940. extreme236
9:03 PM GMT on July 04, 2008
BBL
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939. OUSHAWN
9:02 PM GMT on July 04, 2008
The blow up off Nic. does look mighty impressive. Have a feeling it will probably die off later tonight but if it doesn't it could get very interesting over the weekend in the NW Caribbean.

Looks like there may be a little spin to the blow up in the southern BOC as well. Isn't this where the GFS and NOGAPS were wanting to spin something up in their runs yesterday?
Member Since: September 20, 2007 Posts: 0 Comments: 44
938. MississippiWx
9:01 PM GMT on July 04, 2008
What I've learned through the years is that if the models initially point your way, don't worry. They almost always shift away from their initial direction, sometimes 500 miles from their first point.

Bertha is not a storm to discount just yet.

Also, very interesting flare up of thunderstorms in the Western Caribbean. Probably will die out later, but could get interesting if it persists.
Member Since: July 15, 2006 Posts: 17 Comments: 10285

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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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