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Posted at 2:40 PM ET, 09/ 5/2008

Hanna On Course to Pound Region Saturday

By Capital Weather Gang

Rain odds up tonight; heavy rain & strong winds Saturday

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

hanna-satellite-0905.jpg
Satellite image of Hanna, positioned east of Florida, at 2 p.m. Courtesy NOAA.

Live Chat Transcript

Increasingly tropical conditions are moving into the area on a fresh south wind as highs top out in the upper 80s. Positioned about 310 miles south of Wilmington, N.C., Hanna is slowly strengthening with sustained winds of 70 mph as of 2 p.m. Hanna may become a hurricane prior to landfall, though forward speed has increased to 20 mph meaning the storm only has hours left over water.

The first outer squalls of Hanna are entering southern Va., and they may arrive in the area by evening. After the first band comes through there could be a lull in activity, but showers will occur with more frequency across the area overnight.

The main event comes in late tonight and tomorrow with heavy rains -- 2-4" inches, with locally heavier amounts closer to 6" possible -- that 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.

RAINFALL MAP AND TIMELINE

5 PM FRI to 12 AM SAT
40% chance of showers. Winds sustained from the south and southeast at 10-20 mph.
12 AM SAT to 8 AM SAT
Frequent showers with a few thunderstorms. A couple periods of steady rain. Winds sustained from the northeast at 15-25 mph.
8 AM SAT to 6 PM SAT
Heavy rain bands move through with thunderstorms mixed in. Winds sustained at 20-35 mph. Gusts to 50 mph.
6 PM SAT to 9 PM SAT Steady rain tapers quickly from southwest to northeast. Scattered showers and thunderstorms linger. Winds sustained at 20-30 mph. Gusts to 40 mph.
After 9 PM
Clearing skies and decreasing winds.

Note: The 2-4"+ swath above may need to be expanded westward depending on data that comes in later this afternoon or evening.

USEFUL LINKS

How to Prepare for Flooding, Blackouts and High Winds | Track Hanna | Satellite image | Southeast radar | Northeast radar

STORM FAQ


Estimated sustained winds and gusts Saturday.

How strong will the winds be? Could there be wind damage and power outages?

Occasional strong gusts of over 50 mph could be capable of bringing down some trees and power lines. Scattered power outages are possible in the metro area. The most outages are likely to be near the Bay and to the east.

What precautions should I take?

No need to board up windows. But do ensure outdoor furniture and plants are secured and/or brought inside before you go to bed tonight. Does your sump pump work if your basement leaks? Have a flashlight handy in case the power goes out, and food and supplies that could last you and your family through a day or two without power, which is probably the worst-case scenario we would see with this storm.

How confident are you in your forecast?

Confidence is toward the high side because most computer models are in agreement on Hanna's track. It's doubtful the storm will miss us. There's a small chance it could veer further east than expected and thus leave us with less rain and slightly weaker winds. There is also the chance that Hanna tracks somewhat further west than forecast, shifting the areas of heaviest rain and strongest winds west.

Keep reading for answers to more FAQs about the storm, including the forecast into early next week.

What is the flooding threat?

Widespread, major flooding is not anticipated. But basements, roadways and other low-lying areas that are typically prone to flooding will be at risk, as Hanna could dump several inches of rain in a very short period of time.

Could there be a tidal surge along the Potomac?

The Weather Service is projecting two to four feet of storm surge along the western shore of the Chesapeake Bay and the tidal Potomac River on Saturday. The high tides to watch occur on Saturday morning and evening, but only minor coastal flooding is anticipated.

Could there be tornadoes?

An outbreak of tornadoes does not seem likely. However, it's not unusual for tropical systems to spawn at least a few tornadoes. Stay tuned to Capital Weather Gang during the storm. We'll let you know if any tornado warnings are issued by the National Weather Service.

When and where will the conditions be the worst?

Along and east of I-95, from sunrise through sunset Saturday.

How bad will this be at the Maryland/Delaware beaches?

Sustained winds of 40-60 mph and gusts to 70 mph could mean some flying debris, significant power outages and moderate beach erosion. Rainfall, on the other hand, should be less than here in the metro area. Probably no more than 1-2".

Will this be as bad as Isabel?

Not likely. Isabel produced sustained winds up to near 50 mph in parts of the area and gusts to near 80 mph. Hanna's winds will be weaker. Storm surges will also be lower with Hanna than they were with Isabel. There's a small chance Hanna intensifies a little before landfall which would bring winds closer to the levels of Isabel, but it's doubtful Hanna will close the gap.

When will the storm clear and what's the forecast for Sunday and beyond?

The rain should be over, or quickly coming to an end, and winds dissipating by Saturday evening, with clearing skies Saturday night and lows in the 60s. Sunday looks spectacular -- mostly sunny and breezy with highs in the upper 80s and decreasing humidity. Monday should also be nice, again mostly sunny with highs in the mid 80s and not too humid. Tuesday brings the next chance of showers and thunderstorms (about a 30-40% chance as of now) with a mix of sun and clouds and highs in the 80s.

By Capital Weather Gang  | September 5, 2008; 2:40 PM ET
Categories:  Forecasts, Tropical Weather  
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Next: Hanna Not Quite a Hurricane as Showers Approach

Comments

Winds approaching hurricane force now, according to NHC.

Godspeed Hanna!!

Posted by: Brian in Alex | September 5, 2008 2:56 PM | Report abuse

Absolutely AWESOME post. As was said earlier by several people, you guys are the BEST there is.

I'm actually a bit excited to get this storm. I'll be taking videos and pictures and measurements of the pressure (because I'm a geek like that) tonight and tomorrow.

It'll be interesting to see the storm reports from the commenters tomorrow.

BTW: The pressure is 1006 hPa (hPa is "hectopascals"...it's the same as 1006mb) here as of 3:08PM.

Posted by: weatherdudeVA | September 5, 2008 3:10 PM | Report abuse

I know nothing about clouds. I even forgot what I learned about them in 1st grade. I keep meaning to brush up on my cloud names, but I never do.

Anyway...it's interesting to see all of the different kinds of clouds that are streaming in right now. Different heights, types, densities, and lots of them. Maybe skies this diverse happen a lot and I'm only paying attention now because of Hanna. I dunno.

Posted by: Laura in NWDC | September 5, 2008 3:21 PM | Report abuse

Oh dear. I'm already starting on the chocolate. This is not looking good. I hope Murre and ~sg will be around to help me through it....

Posted by: tinkerbelle | September 5, 2008 3:29 PM | Report abuse

Has the Naval Academy redeployed their 'fleet'? Usually in storms they take all their boats up the Severn a bit but not sure if they are worried about this one or not.

Posted by: PenguinSix | September 5, 2008 3:36 PM | Report abuse

OK, I'm going to be one of those people asking about my personal situation. I'm supposed to be going to the VT game down in Blacksburg tomorrow. I'm not too worried about the actual game time weather there as I imagine they'll be on the outer fringes. What I am concerned about is getting there, we plan to leave at 7am to be down there by noon. How bad will it be then and how long will we be in the bad weather, will we be out of the very heavy rain and wind by I-81? I'm leaning towards bagging it b/c the thought of the beltway and 66 in driving rain and wind sounds like no fun at all.

Posted by: Ana B | September 5, 2008 3:46 PM | Report abuse

Thank You Lord for sending us swell!

Posted by: James | September 5, 2008 3:54 PM | Report abuse

Tinkerbelle:
I would give a 30% chance of D.C. receiving Tropical Storm winds (sustained over 39 mph). The almost impossible part of this equation is at what latitude recurvature occurs? This will have a huge impact on wind speeds in the D.C. vicinity tomorrow.

As I speak, Hanna is around 270 miles south of Wilmington, and approx. 12 hrs. away from likely landfall.

Considering the warm gulfstream waters, I feel it will probably gain cat.1 status before landfall.

Posted by: Augusta Jim | September 5, 2008 4:04 PM | Report abuse

To revive memories of Isabel, tis is a NWS link with good graphics and animations, http://www.nhc.noaa.gov/archive/2003/ISABEL_graphics.shtml
Also Agusta Jim, why would there be a tropical storm warning if there was only a 30% percent chance of t.s. force winds?

Posted by: sam | September 5, 2008 4:07 PM | Report abuse

The 12Z run of the NAM this morning was considerably less wet than the 12Z GFS. A first peek at the 18Z NAM run suggests even less precipitation for the area. It will be interesting to see if the 18Z GFS also makes a correction.

The HPC's QPF forecast has strongly favored the wetter GFS solution...

I do think this is a situation where localized rainfall totals could vary significantly based on location and where strong rain bands or squalls set up. I wouldn't be shocked if there's a 2-4" difference in rainfall amounts over a short 15mi distance.

Posted by: Josh, Capital Weather Gang | September 5, 2008 4:20 PM | Report abuse

Ana B, I'm heading down 2 B'burg from Spotsy. about 9 am. I don't expect any problems going or coming back. B'burg shouldn't b 2 bad, they will b on the fringe. I don't expect the more than 1 - 1.5" of rain along the 95 corridor. Less 2 the W more 2 the E.

Posted by: VaTechBob. | September 5, 2008 4:31 PM | Report abuse

I'm excited for this storm. I just moved back to the area from San Diego, CA, where they don't have any weather. Hanna should bring some impressive down poars and strong winds, but not enough to cause mass damage. It should be a fun ride.

Posted by: Dude | September 5, 2008 4:32 PM | Report abuse

We're getting a lot of questions: "I'm driving to x location, will I be OK?" The bottom line is that if you've driven in thunderstorms with driving rain and gusty winds, you've experienced what we're going to experience tomorrow. Yes-- you will probably be ok, but there is added risk due to reduced visibility, possible debris (from tree limbs, etc) and the potential for skidding/hydroplaning.

Posted by: Capital Weather Gang | September 5, 2008 4:44 PM | Report abuse

I forgot to mention that I, personally, think the higher precipitation amounts are more likely. Model QPF for tropical systems is frequently underdone. My guess is that many locations will see 3-4"; some amounts closer to 6" or 8" are possible, especially to the southeast of DC. Note, these are my own prognostications.

Posted by: Josh, Capital Weather Gang | September 5, 2008 4:52 PM | Report abuse

Josh, I hope the NAM is correct over the GFS. The prospect of 3-6" of rain does not sound good for my basement.

Posted by: David A. in Staffod | September 5, 2008 4:54 PM | Report abuse

Sorry about the previous typo with my location. We need a spell checker for the comment portion of this site :-)

Posted by: David A. in Stafford | September 5, 2008 4:56 PM | Report abuse

Just be careful out there. High winds can be very unpredictable. I was walking my two dogs back in Feb and a huge branch slammed into my lower back from 60 ft. Broken back, serious internal bleeding and nerve damage for the rest of my life, are what became of a nice breezy day. Stay safe!

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

How is this weather going to affect my dove hunting tomorrow? Will the birds be flying? I don't mind getting wet.

Posted by: Fairfaxboy | September 5, 2008 5:02 PM | Report abuse

I just noticed the 5pm NHC track takes Hanna a bit further east. I am not sure if that means a lot for us, so I will defer to the CWG experts.

Posted by: David A. in Stafford | September 5, 2008 5:03 PM | Report abuse

@tinkerbelle: The boat is as secure as I can make her, but I'm lower than I'd like on chocolate for this storm....have an extra bite for me, please!

Posted by: ~sg | September 5, 2008 5:07 PM | Report abuse

yo homes, wuzzup i love the hurricane

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

Josh-- I agree a general 3-4" sounds about right--with locally higher amounts. I'm not a big fan of using the NAM for tropical systems as it very poorly simulates them compared to the global models.

David A.: The current NHC track forecast is consistent with our forecast track--and the impacts we expect as a result.

Posted by: Jason, Capital Weather Gang | September 5, 2008 5:17 PM | Report abuse

Hi. I plan to construct an intricate model home out of precariously balanced toothpicks in my backyard tomorrow afternoon. Should I cancel?

Posted by: Concerned Citizen | September 5, 2008 5:23 PM | Report abuse

Thanks for the clarification, Jason.

Posted by: David A. in Stafford | September 5, 2008 5:29 PM | Report abuse

@ ~sg and tinkerbelle -- Reporting for duty. I have an entire uneaten bar of chocolate at home.

I'm preparing for a power loss of up to half a day, so I have small aseptic milk containers for cereal and tea, plenty of ice, a cooler at the ready. I'm hoping our gutters are not overwhelmed, and that our basement stays dry (so far it has).

Posted by: Murre | September 5, 2008 6:17 PM | Report abuse

A bit of light rain is falling here, and it's mostly calm right now on the edge of Takoma Park.

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

Concerned Citizen: you should be fine. Just make sure you have eye protection. :-)

Posted by: mcleaNed | September 5, 2008 8:15 PM | Report abuse

The comments to this entry are closed.

 
 
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