Communicating objective guidance for TC forecasting –

Evolving operational practices and techniques

Chris Fogarty

Canadian Hurricane Center (CHC), Halifax, Nova Scotia, Canada

Outline of topics• How availability of NWP to general audiences online has changed the job of operational forecasting

• Early notification - communication of pre-storm and long-range TC forecasts

• Tools for in-season prediction and how to package for the media and stakeholders

• Communicating probabilities (track, wind)

• Role of real-time reporting from social media in the forecast process

• Future map products for effective communication of rain/wind warnings

Key changes over past decade• Increase in media attention (over increasingly longer timescales)

• Availability of forecaster tools (display of NWP online, weather blogs, private sector agencies)

• Advancement of official forecast products

• Users are asking more (and more specific) questions

• Changes in how forecast information is used – e.g. GIS display / users ability to display/modify “met objects”

Operational timescales and communications

Canadian Hurricane Center operations timescale and primary communication medium (red):

T-3 monthsPre-seasonForecast(late May)Media briefing

T-1 monthIn-season updates(media requests)state of environmentinterviews

T-10 daysStorm formationUpdate (media/EMStakeholders) + internal Email product (10-day outlook)

T-7 daysStorm formationUpdate (media/EMStakeholders)Interviews/email/phone

T-5 days prior to storm arrival east. Canada – mediaramps up – interviews/phone

T-4 daysGeneral stmt – notrack table or details – descriptive

T-3 daysCHC begins 24-7 staffing issuing general and technical stmts /track map

T-1.5 days issueWatches in coord.with NHC phone/email/NWSChat

T-1 day issueWarnings bulletins andIntermediate (3-hrly)stmts; impact stmts

T+1 day storm summary bulletinand wrap-up; datacollection; debriefings

Late May briefing – seasonal outlook primary visuals used by the CHC

Focusregionsduring themedia briefing

In-season products used for communication of TC formation potential and flow pattern

• Main products (TC genesis parameters) that are checked are Paul Roundy’s site and CIRA/RAMMB

• Flow pattern-related and genesis anomaly fields particularly useful

• Images are used to prepare text for internal email product or for media interviews

In-season email product

• Sample of ~10-day outlook email gleaned from the objective products

• Stakeholders often request this sort of “official” word from the Hurricane Center

• As an internal product, it is referred to as “High Interest” statement intended as a heads-up for government planning

• TROPICAL OUTLOOK (AFTERNOON OF SEPT 5): MOISTURE REMNANTS FROM TROPICAL STORM LEE WILL CONTINUE FEEDING INTO A FRONT BRINGING HEAVY RAINFALL OVER SOUTHERN QUEBEC, NEW BRUNSWICK AND NORTHERN NEWFOUNDLAND EARLY THIS WEEK. THIS COULD CAUSE FLOODING/MEDIA INTEREST SINCE THE REGION WAS RECENTLY SATURATED BY RAINFALL FROM IRENE. MEANWHILE, HURRICANE KATIA WILL MOVE NORTHWESTWARD AND WILL LIKELY GENERATE SOME MEDIA INTEREST. THE STORM WILL SPREAD LARGE WAVES AND SPECTATOR INTEREST ALONG THE ATLANTIC COAST OF NOVA SCOTIA MID TO LATE WEEK. IF KATIA AFFECTS LAND AREAS (WIND/RAIN) IT WOULD LIKELY BE IN THE FRIDAY-SUNDAY TIMEFRAME (SEPT 9-11).

• might be useful as a public product? (like NHC’s Tropical Weather Outlook)

General statements ~T-4 to 5 days• Often consult NHC 34-kt and 64-kt wind probability fields• Media is often fully-engaged at this point (especially for long-lived storms)• They want numbers, so we give them probability values

“Danny” 2009 – TS-force prob: “Danny” 2009 – Hurr-force prob:

Probabilistic information in textual form (T-4 days):TROPICAL STORM DANNY PRELIMINARY DISCUSSION:

TROPICAL STORM DANNY HAS FORMED NORTH OF THE BAHAMAS AND IS EXPECTED TO DEVELOP INTO A CATEGORY 1 HURRICANE BY THE WEEKEND AS IT MOVES NORTHWESTWARD TOWARD THE SOUTHEASTERN U.S. THE STORM IS IN ITS EARLY STAGES OF DEVELOPMENT AND THERE REMAINS A VERY LARGE DEGREE OF UNCERTAINTY IN BOTH TRACK AND INTENSITY. MUCH OF THAT UNCERTAINTY IS ATTRIBUTABLE TO THE FACT THAT DANNY IS STILL IN ITS DEVELOPMENT STAGE. COMPUTER MODELS ARE INDICATING THAT THE STORM COULD BECOME A WEAK HURRICANE (ABOUT A 40% CHANCE OF THAT) THEN ACCELERATE TOWARD THE NORTHWEST THEN NORTHEAST. DANNY WOULD LIKELY UNDERGO TRANSITION TO A POST-TROPICAL STORM AS IT MOVES NORTH TOWARD THE U.S. OR EASTERN CANADA. THE ATMOSPHERIC ENVIRONMENT AROUND THE STORM ONLY SUPPORTS GRADUAL STRENGTHENING OVER A 2 TO 3-DAY PERIOD BEFORE EITHER MAKING LANDFALL IN THE US OR ACCELERATING TOWARD THE MARITIMES.

THE FIRST OFFICIAL FORECAST OF DANNY FROM THE NATIONAL HURRICANE CENTRE IN MIAMI INDICATES A POST-TROPICAL STORM WITH POSSIBLE HURRICANE-FORCE WINDS APPROACHING THE MARITIMES LATE SATURDAY NIGHT/EARLY SUNDAY. THAT IS JUST AN EARLY FORECAST CONTAINING MUCH UNCERTAINTY WITH ONLY A 5-10% CHANCE OF HURRICANE FORCE WINDS AFFECTING THE MARITIMES AT THIS STAGE. COMPLETE BULLETINS FROM THE CANADIAN HURRICANE CENTRE ARE SCHEDULED TO BEGIN AT 9 AM ADT ON THURSDAY.

Key explanation of NHC’s forecast which contained a 65-kt hurricane-strength system at the day-4 mark:

“ONLY A 5-10% CHANCE OF HURRICANE FORCE WINDS AFFECTING (EASTERN CANADA)”

Challenge when thereis a mix of deterministic and probabilistic products

“Danny” 2009

NHC Map

CHC Map

Ensemble oftracks is used todescribe range to public and stake-holders – e.g.:

“landfall possible from eastern Maine tosouthern Newfoundland”

Gives them a realisticdepiction of the uncertainty range associated witha given storm

T-3 days

http://derecho.math.uwm.edu/models/

Shapefile sample This season we will haveshapefiles for plotting in google maps/earth

New software to producespecific maps such as --->will have much more controlthan with old production software

Established practices & phrasing used by the CHC (irrespective of objective guidance/NWP)

> 2 days lead time:- Refrain from rainfall/wind speed values…keep descriptive / qualitative

48 to 24 hours:- Forecast ranges introduced – e.g. wind gusts up to …; rainfall

amounts from X to Y mm

24 hours or less:- Impact statements introduced where confidence is greatest- Canned phrasing for specific phenomenon such as rip tides/currents

and barotropic waves for rapidly-moving TCs

Forecaster reference tables (NWP-independent):

Social media role: real-time monitoring

• Weather forums, Twitter, Facebook, office obs email inbox (HAM radio reports, volunteer observers)

• Summarized in bulletin updates (3-hrly frequency)

• For use during media interviews – important for credibility (real-time awareness -> short-range forecast tuning)

• MASAS (multi-agency (multi-reporting) situational awareness) – one stop shop for observations – pilot program in our weather offices

Future track map sampleparticularly useful when dealing with extratropical transition and

asymmetric transformation of wind/rain

Questions/Discussion