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Posted at 5:35 PM ET, 09/ 5/2008

Hanna Not Quite a Hurricane as Showers Approach

By Capital Weather Gang

Ike and Josephine on Hanna's Heels

*Tropical Storm Warning issued for metro area and Eastern shore.*
*Flash Flood Watch for metro area Saturday morning through evening*

Clouds associated with Tropical Storm Hanna -- as of 5 p.m. a strong tropical storm with winds of 70 mph, just short of the 74 mph needed to be a hurricane -- are streaming overhead D.C. and vicinity this early evening, and the first showers are approaching from the south, even as the storm's center is 160 miles south-southeast of Charleston, S.C. The metro area will see about a 40-50% chance of showers during the early evening, with steady rains and increasing winds moving in as the night goes on.

The latest track from the National Hurricane Center has shifted slightly to the east, but that doesn't change the overall impacts we expect for the region. By tomorrow evening, 2-4" inches of rain is possible, with locally heavier amounts closer to 6", That much rain in a short period of time could cause flooding in spots. Winds may reach sustained speeds near 35 mph with occasional gusts to around or above 50 mph. Overcast skies will limit highs tomorrow to the 70s.

Keep reading for the latest on Hurricane Ike and Tropical Storm Josephine. See our comprehensive assessment of Hanna that includes a storm timeline, rainfall potential, wind projections, and frequently asked questions.

HURRICANE IKE

Hurricane Ike continues to churn out in the Atlantic, possibly on a collision course with the Northern Caribbean on Sunday and potentially South Florida early next week. While not as strong as it once was, it still maintains status as a major hurricane (Category 3) with sustained winds of 115 mph.

For the near future, Ike is expected to continue on its westerly (or just south of westerly) track as it is trapped beneath a strong ridge encompassing the western Atlantic. After Hanna departs the scene, the ridge is expected to back-fill west and be the main steering influence for Ike, keeping it suppressed to the south. The longer the ridge holds together and the stronger it becomes, the more south or west Ike will travel before starting an eventual turn to the north. If the ridge were to deteriorate quicker than expected, Ike could turn more quickly to the north, brining East Coast interests into play.


Satellite video of Hanna, positioned east of Florida this morning taken from the ISS via CNN.

TROPICAL STORM JOSEPHINE

Josephine is currently a storm in disarray out in the Atlantic Ocean, undergoing attack from wind shear that threatens to tear it apart. This should remain the case over the next few days, at which point conditions should turn more favorable for strengthening, assuming Josephine has survived this current beating. Josephine is expected to continue its movement toward the northwest, but is probably at least a week away from affecting any land mass.

By Capital Weather Gang  | September 5, 2008; 5:35 PM ET
Categories:  Forecasts, Tropical Weather  
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Next: Showers Streaming In Ahead of Hanna

Comments

Clouds: mainly Cu moving S to N with Ac cumulogenitus and some Ci. I did not see the type of progressively advancing cirrus invasion from the SE generally associated with tropical systems of this type.

Posted by: El Bombo | September 5, 2008 5:46 PM | Report abuse

Since we rarely have heavy wind around here i'm not really sure what the effect of sustained 30+ mph winds will be. Would you guys suggest bringing lawn furniture inside (chairs, grill, tables), or do you think that some items will be OK left outside?

Godspeed Hanna!!

Posted by: Brian in Alex | September 5, 2008 5:58 PM | Report abuse

Brian, my philosophy is it's better to be safe than sorry. I'd certainly secure lighter items like chairs and would consider also securing your grill & table (depending somewhat on how heavy -- i.e., wind resistant they are).

Also, if your house is prone to flooding, and you haven't already checked your gutters to make sure that they're clear of debris, then I'd do that too.

Posted by: Josh, Capital Weather Gang | September 5, 2008 6:06 PM | Report abuse

Clouds have gotten WAY thick. Looks like a storm is coming!

Posted by: Laura in NWDC | September 5, 2008 6:18 PM | Report abuse

El Bombo, the sky over Harpers Ferry was all cirrus clouds, lots of them (really beautiful), when I was out walking mid-morning. Maybe unrelated cirrus, that far ahead of the storm?

Murre and ~sg, good to see y'all on board! I'll be reading you.

Posted by: tinkerbelle | September 5, 2008 6:32 PM | Report abuse

Hey folks, Charleston is in SOUTH Carolina, not NC!!

Posted by: marhar | September 5, 2008 6:52 PM | Report abuse

Judging from the latest GOES visible loop and Charleston radar, it appears Hanna has taken a jog to the west, the center appears to be at 31.5 N and 79.3 W at the moment. This is about 30 or so miles west of the forecast path, not sure how that will affect the projected path. At this point, radar, reconnaissance reports, and satellite are usually more helpful in figuring out what's going to happen than the forecast models.

Posted by: Steve Wasko | September 5, 2008 6:55 PM | Report abuse

i'm hopin for sustained winds of 40-50 mph with gusts of 65, not enough to do major damage but would be cool.

Posted by: gideon | September 5, 2008 7:01 PM | Report abuse

Latest GOES IR loop shows an impressive CDO and what looks like an eye forming. Very possible considering the ocean temp off Myrtle Beach is 86 degrees. Wouldn't be suprised to see NHC upgrade Hanna for the 8 PM advisory.

Posted by: Steve Wasko | September 5, 2008 7:03 PM | Report abuse

There were a lot of beautiful cirrus clouds in Arlington around 4:30 p.m., at least in the west-ish sky (looking down Lee Highway).

Now the clouds are much thicker and someone with better identification skills than I would have to tell me what kinds of clouds they are! (I at least know that they look really cool).

Posted by: dinergirl | September 5, 2008 7:06 PM | Report abuse

Other outlets are calling for the low end of your rainfall prediction. I just saw Channel 4, which is predicting 2-3", or less is the storm tracks further east. TWC says 2"

Posted by: steve takoma park md | September 5, 2008 7:21 PM | Report abuse

never trust the weather channel. they always underrate stroms. for example, in th past 2 years they never predicted more than 2 inches of snow and they predict winds of only 15 mph.

Posted by: sam | September 5, 2008 7:28 PM | Report abuse

Hanna has really developed over the past few hours and an eye seems to have formed on the latest satellite frames. The storm has got to be a hurricane with winds of at least 80 mph. I would be surprised if the 8 pm NHC advisory hasn't upgraded Hanna to a hurricane. I concur with Steve that the storm center appears to be to the west of the forecast track. All of this seems to be good news for DC severe weather lovers.

Godspeed Hanna!!

Posted by: Brian in Alex | September 5, 2008 7:50 PM | Report abuse

As I had mentioned in the chat session, predicting the AMOUNT of rain at a specific location - not just whether it's going to rain or not - is one of the most difficult problems in meteorology.

No one can reliably discriminate with any reasonable degree of confidence in forecasts - even only one day ahead - between, for example, between 2" and 2-3" or less than/greater than 3-4".

That includes our experts at CWG (sorry guys). Yes, we can say with virtual certainty it will be a major, long duration rain event, as opposed to a brief heavy thunder shower, or day of generally light and steady rain - but not the actual amount to even a few inches. There are simply too many variables and interactions to sort out even with today's state of the art models and/or by the most experienced human forecasters. The time may come when our capabilities will be significantly improved, but we're not there yet.

So, trying to make something meaningful of the varying forecasts that are out there might be fun, but in reality it is an exercise futility. It's just another weather fact of life!

Posted by: Steve Tracton | September 5, 2008 7:50 PM | Report abuse

36A just came out--she's still a TS at 70 mph.

Posted by: John | September 5, 2008 7:57 PM | Report abuse

LAIR!!!

Posted by: gideon | September 5, 2008 8:00 PM | Report abuse

To give an example of how difficult tropical systems can be to forecast, one need only look at Hanna's current position in comparison to the NHC's 3-day forecast cone from today's 5 pm advisory. A storm's position is expected to remain within the forecast cone ~66% of the time through 3 days. Yet within 3 hours of today's 5 pm advisory, Hanna had already moved outside the cone.

Posted by: Brian in Alex | September 5, 2008 8:15 PM | Report abuse

Brian: moved west? That WOULD be big news for us, and a possible sign of further shifts in the track to come.

8:35 pm: 535 Dominion Electric customers without power (out of 2.4 million). Expect that number to shoot up within the next dozen hours.

Posted by: mcleaNed | September 5, 2008 8:26 PM | Report abuse

Steve- I think you can quite credibly provide a range for the average amount of rain over a large area. The same goes for snow. We have done it successfully over the years and so have countless other forecasters, including the NWS. I agree that you can't pinpoint an exact amount over a given location, but indicating a general 2-4" of rain is likely with isolated higher (and lower amounts) is well within our current capability.

Posted by: Jason, Capital Weather Gang | September 5, 2008 8:36 PM | Report abuse

170 NoVA Dominion customers have lost power within the last 4 or 5 minutes. (See the outage summary here: http://www.dom.com/news/outage_sos.jsp )

Posted by: mcleaNed | September 5, 2008 8:40 PM | Report abuse

Greetings from sunny LA.....out here on a TV shoot for work with a planned flight tomorrow morning from LAX to IAD. Supposed to be landing around 3:30pm. Keeping track of the storm....and how screwed I might be for my flight home.

I'm not going to ask about any aviation delays....but I will put out the question of "am I in danger of an outright cancellation?"

Posted by: Jamie C in Chevy Chase DC | September 5, 2008 8:50 PM | Report abuse

I'm looking at the satellite loops on Hanna, with the forecast track points turned on. From that it looks like Hanna is tracking quite a bit west of the forecast points. Am I reading that correctly ?( and yes I know that it doesn't really "matter" for practical purposes).

Posted by: MDScot | September 5, 2008 9:08 PM | Report abuse

MD Scot- as of 8 pm, Hanna was 40 miles west of where the NHC forecast it would be. It appears to have maintained this distance over the past couple of hours. Whether or not this means that the 11 pm forecast track will be shifted west, I don't know. The models, which have been going back and forth all day, do seem to be trending west again for the time being, so that is a good sign.

Posted by: Brian in Alex | September 5, 2008 9:50 PM | Report abuse

Jamie C in Chevy Chase, you are absolutely in danger of an outright cancellation. Call your airline tonight; I guarantee you that they're already shifting schedules around. Don't wait for them to decide when you travel - let them know you're interested, and you'll have increased chances of influencing when you get a flight.

Posted by: ~sg | September 5, 2008 10:00 PM | Report abuse

Map of CONUS airport delays in real time: http://www.fly.faa.gov/flyfaa/usmap.jsp

Posted by: ~sg | September 5, 2008 10:02 PM | Report abuse

Jason, I don't disagree - yes, one can provide credible predictions of average rainfall in terms of a range of amounts over a large area. The devil, though is in the details - what is credible and what size the area. Whatever, the the graphics displayed are generally reliable for providing the broader perspective of possibilities.

But some, as seen in the comments and chat session, are interested only in location specific forecasts. My comments above were directed there - for all intents and purposes it can't be done with any meaningful degree of reliability.

To readers, it's important to recognize the critical difference in skill in quantitative rainfall forecasts between areal averages over an area versus location specific predictions

Thanks Jason for pointing out the lack of completeness in my previous response

Posted by: Steve Tracton | September 5, 2008 11:03 PM | Report abuse

Steve- I with you 100% now. We're on the same page. Along these lines, note this interesting comment from NWS Sterling:

WITH AVERAGE TRACK ERRORS STILL NEAR 40 NAUTICAL MILES EVEN AT 12 HRS STILL DIFFICULT TO SAY WHERE EXACTLY HEAVIEST RAINS WILL OCCUR. MODEL GUIDANCE STILL
INDICATING A SWATH OF 5+INS SOMEWHERE ACROSS OUR AREA. GIVEN THAT MODEL GUIDANCE IS ALWAYS UNDERDONE IN QPF AMTS ASSOCIATED WITH TROPICAL SYSTEMS WOULD NOT BE SURPRISED TO SEE SOME 8+INCH TOTALS. THIS STORM ALSO HAS A VERY SIMILAR TRACK TO HURRICANE FLOYD IN 1999 WHEN 6+INS WITH ISOLD TOTALS TO A FOOT OCCURRED.

Posted by: Jason, Capital Weather Gang | September 6, 2008 12:25 AM | Report abuse

The comments to this entry are closed.

 
 
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