Enhanced Enhanced Northeasterly Winds Northeasterly Winds

in the Western Gulf of in the Western Gulf of MaineMaine

Daniel MichaudDaniel MichaudSamuel MillerSamuel Miller

Plymouth State UniversityPlymouth State University

Dan St. JeanDan St. JeanNOAA/NWS Gray MENOAA/NWS Gray ME

NROW IX – November 7, 2007NROW IX – November 7, 2007

COMET Partners ProjectsCOMET Partners Projects

2 COMET Partners grants have 2 COMET Partners grants have supported this research in 2006-07 supported this research in 2006-07 and 2007-08and 2007-08

6 PSU students, 1 PSU professor and 6 PSU students, 1 PSU professor and 2 NWS forecasters have collaborated 2 NWS forecasters have collaborated on this researchon this research

OutlineOutline

Introduction and BackgroundIntroduction and Background MethodologyMethodology ResultsResults PredictabilityPredictability Conceptual Models Conceptual Models Future WorkFuture Work SummarySummary AcknowledgementsAcknowledgements

Area of StudyArea of Study

– Map courtesy of GoMOOSMap courtesy of GoMOOS

The Northeasterly Wind The Northeasterly Wind PhenomenonPhenomenon

A near-surface, near-shore, A near-surface, near-shore, mesoscale band of enhanced mesoscale band of enhanced northeasterly wind in the western northeasterly wind in the western Gulf of Maine (GoM)Gulf of Maine (GoM)

This flow is not predicted well by This flow is not predicted well by NWP or forecasters…and is typically NWP or forecasters…and is typically under-forecastunder-forecast

Why Study This Why Study This Phenomenon?Phenomenon?

Some possible ramifications of the Some possible ramifications of the under-prediction of northeast winds:under-prediction of northeast winds:– Increased wave heights, both due to Increased wave heights, both due to

higher winds and longer durationhigher winds and longer duration– Increased storm surge during larger Increased storm surge during larger

eventsevents

All of the above can put property All of the above can put property and life at risk, especially when and life at risk, especially when the conditions deviate significantly the conditions deviate significantly from the forecastfrom the forecast

Example – 23 May 2005Example – 23 May 2005 A Small Craft Advisory and then a Gale Warning A Small Craft Advisory and then a Gale Warning

were raised for the western GoM coastal waterswere raised for the western GoM coastal waters– A tight gradient northwest of a deep cyclone in the A tight gradient northwest of a deep cyclone in the

GoMGoM Winds increased and far exceeded all human Winds increased and far exceeded all human

and numerical predictionsand numerical predictions– $1M USD in damage to marinas and beaches$1M USD in damage to marinas and beaches

Peak MOS winds were ~20 kts, peak forecaster Peak MOS winds were ~20 kts, peak forecaster winds were 20-25 kts for the 24 hrs prior to winds were 20-25 kts for the 24 hrs prior to event onsetevent onset

Winds peaked at 46G51 kts at Matinicus Rock Winds peaked at 46G51 kts at Matinicus Rock (MISM1), 43G49 kts at Isles of Shoals (IOSN3)(MISM1), 43G49 kts at Isles of Shoals (IOSN3)- Over 12 hours of winds greater than 30 kts in Over 12 hours of winds greater than 30 kts in

GoMGoM

BackgroundBackground

Apffel (2006) showed in a GYX study:Apffel (2006) showed in a GYX study:– NWP, and consequently human NWP, and consequently human

forecasters, do not capture these forecasters, do not capture these northeast wind events wellnortheast wind events well

– Guidance consistently under-predicts Guidance consistently under-predicts northeast winds in the western GoMnortheast winds in the western GoM

– In northeast flow…GFS MOS has a bias In northeast flow…GFS MOS has a bias of -5kt and mean error of 4kt of -5kt and mean error of 4kt A cause for concern and studyA cause for concern and study

Example of GFS MOS BiasExample of GFS MOS Bias

- This is a graph of GFS MOS error and bias over a 1.5 year period at Isle of Shoals (IOSN3)

- The largest model error was seen in NE flow

- A strong negative bias in flow speed was also observed in NE flow

Apffel, 2006

ETA MOS has the same negative bias in NE flow…so what do

forecasters use?

BackgroundBackground Why doesn’t MOS – and other guidance – not Why doesn’t MOS – and other guidance – not

handle NE winds well in the GoM?handle NE winds well in the GoM? Possibly due to sub-grid scale phenomena (coastal front, Possibly due to sub-grid scale phenomena (coastal front,

terrain effects) not being handled well by NWPterrain effects) not being handled well by NWP Shallow air masses (typically arctic/polar in nature) cause Shallow air masses (typically arctic/polar in nature) cause

mesoscale northeast winds that are not shown well by mesoscale northeast winds that are not shown well by modelsmodels

Small, elusive coastal fronts/baroclinic zones can Small, elusive coastal fronts/baroclinic zones can significantly increase wind speed and affect flow direction significantly increase wind speed and affect flow direction over the coastal watersover the coastal waters

Biased model output creates a systematic Biased model output creates a systematic error in which the forecasters under-forecast error in which the forecasters under-forecast both wind speed and duration in NE flow over both wind speed and duration in NE flow over the GoMthe GoM

BackgroundBackground

Previous studies by Apffel (2005), Previous studies by Apffel (2005), Moker (2006) and Michaud (2006, Moker (2006) and Michaud (2006, 2007) have shown that both synoptic 2007) have shown that both synoptic and mesoscale pattern recognition and mesoscale pattern recognition can prove useful in detecting these can prove useful in detecting these eventsevents

BackgroundBackground

Using these prior studies it was Using these prior studies it was determined:determined:– The synoptic The synoptic andand mesoscale mesoscale

conditions are importantconditions are important– The wind events are likely caused by The wind events are likely caused by

a combination of synoptic and a combination of synoptic and mesoscale forcingmesoscale forcing

– An expected outcome includes an An expected outcome includes an improved technique to forecast these improved technique to forecast these wind eventswind events Including improving forecaster Including improving forecaster

focus/situation awareness leading up to a focus/situation awareness leading up to a possible eventpossible event

MethodologyMethodology

5-year dataset of wind observations 5-year dataset of wind observations from both onshore and offshore stations from both onshore and offshore stations was usedwas used

Criteria :Criteria :– Sustained wind in excess of 6 msSustained wind in excess of 6 ms-1-1 at all at all

three offshore stations (IOSN3, 44007, three offshore stations (IOSN3, 44007, MISM1) concurrentlyMISM1) concurrently

– Wind direction between 15 and 75 degrees Wind direction between 15 and 75 degrees truetrue

– The above conditions must be met for 3 The above conditions must be met for 3 consecutive hours to begin an eventconsecutive hours to begin an event

– A break of one station for one hour was A break of one station for one hour was allowed to continue as a single eventallowed to continue as a single event

MethodologyMethodology

Based on those criteria there were more than 100 Based on those criteria there were more than 100 wind events totaling over 500 hourswind events totaling over 500 hours

Synoptic classification scheme was created which Synoptic classification scheme was created which could explain the pre-onset evolution of these eventscould explain the pre-onset evolution of these events

Vertical wind structure, surface wind and Vertical wind structure, surface wind and temperature, surface sea-level pressure pattern temperature, surface sea-level pressure pattern analyzedanalyzed– This was done to find the cause of forcing for wind events, This was done to find the cause of forcing for wind events,

e.g. coastal front or baroclinic zone, shallow frontal surface, e.g. coastal front or baroclinic zone, shallow frontal surface, shallow high pressure/cold air mass, synoptic flowshallow high pressure/cold air mass, synoptic flow

Used various datasets ranging from NARR to archived Used various datasets ranging from NARR to archived upper air soundings to surface analyses/observationsupper air soundings to surface analyses/observations– NWS marine verification program showed model biases in NE NWS marine verification program showed model biases in NE

flowflow

How have the events been How have the events been classified?classified?

Moker (2006) Moker (2006) quadrant systemquadrant system

Each case was Each case was placed into a placed into a synoptic synoptic classification based classification based on its orientation on its orientation relative to these relative to these quadrantsquadrants

Example: Scenario 1Example: Scenario 1

- This is the case that is most obvious for a northeast flow over the western GoM

- However, this scenario only accounts for 26% of all cases

- Flow is near-geostrophic in the GoM

LEGEND:

7 : 925 hPa wind maximum

(m/s)

Times are in hours before

onset

Last wind maxima is at event onset,

previous maxima plotted

every 12 hrs

Synoptic Classification Synoptic Classification ResultsResults

Synoptic classification system works Synoptic classification system works for rough pattern recognition within for rough pattern recognition within 24-48 hours24-48 hours

Still doesn’t explain the key Still doesn’t explain the key mesoscale features responsible for mesoscale features responsible for the enhanced NE windsthe enhanced NE winds– Synoptic-scale pressure gradients are Synoptic-scale pressure gradients are

too weak to explain what’s happening too weak to explain what’s happening on the mesoscaleon the mesoscale

Example of a synoptically-Example of a synoptically-driven eventdriven event

Winds at 925 and 1000hPa are both NE

Deepening synoptic lowto the southeast

Northeast winds @ 10-20 kthave developed from the

Maritimes through all of NewEngland and coastal watersNo presence of a coastal

front or baroclinic zone

Example of a shallow cold air/Example of a shallow cold air/surface high pressure-driven eventsurface high pressure-driven event

Westerly 850 hPa flow at 15 kt

Flow turns to a light E flow at 5 kt

1000 hPa flow out of NE at 10 kt

Surface winds NE 15-20 kt after

frontal passage

HH

Temps near 45° offshore30° at coastal locations0° on Canadian border

Strong baroclinic zone alongcoastal plain

Coastal Front Case Coastal Front Case Study:Study:

26 December 200426 December 2004

26 December 2004 Event26 December 2004 EventT-24h T-12h T-0h

26 December 2004 Event26 December 2004 Event

T-24h T-12h T-0hNortheast winds have begun blowing, as a

low pressure develops near Tampa FL

A trough ahead of the storm focuses higher

winds and surface convergence

Very strong northeast winds hit the GoM, gusts

to 56 kts at several buoys, sustained to 45 kts

Forecasters expect 30-40 kt winds, raise

gale warning

A storm warning is raised only after the near-coast

winds increase well beyond guidance and forecast

Forecasters expect winds to reach gale

force (30-35 kt), matching guidance

26 December 2004 Event26 December 2004 EventT-36hrT-36hr::SUN...E WINDS 10 TO 15 KT...BECOMING NE 15 TO 20 KT IN THE AFTERNOON. SUN...E WINDS 10 TO 15 KT...BECOMING NE 15 TO 20 KT IN THE AFTERNOON.

SEAS 4 TO 6 FT.SEAS 4 TO 6 FT.SUN NIGHT...NE WINDS SUN NIGHT...NE WINDS 15 TO 20 KT15 TO 20 KT WITH WITH GUSTS TO 25 KTGUSTS TO 25 KT. SEAS 5 TO 8 FT.. SEAS 5 TO 8 FT.MON...NE WINDS MON...NE WINDS 20 TO 25 KT20 TO 25 KT...DECREASING TO 15 TO 20 KT IN THE ...DECREASING TO 15 TO 20 KT IN THE

AFTERNOON. SEAS 3 TO 6 FT. AFTERNOON. SEAS 3 TO 6 FT.

T-12hrT-12hr: Small Craft Advisory: Small Craft AdvisorySUN...NE WINDS 20 TO 25 KT...INCREASING TO 25 TO 30 KT. SEAS 5 TO 8 FT.SUN...NE WINDS 20 TO 25 KT...INCREASING TO 25 TO 30 KT. SEAS 5 TO 8 FT.SUN NIGHT...N WINDS 25 TO 30 KT...INCREASING TO SUN NIGHT...N WINDS 25 TO 30 KT...INCREASING TO 30 TO 35 KT30 TO 35 KT. SEAS 7 TO 10 . SEAS 7 TO 10

FT.FT.MON...N WINDS MON...N WINDS 30 TO 35 KT30 TO 35 KT WITH WITH GUSTS TO 40 KTGUSTS TO 40 KT. SEAS 7 TO 10 FT. . SEAS 7 TO 10 FT.

T-6hrT-6hr: Gale Warning: Gale WarningTODAY...NE WINDS 25 TO 35 KT. SEAS 6 TO 10 FT.TODAY...NE WINDS 25 TO 35 KT. SEAS 6 TO 10 FT.TONIGHT...NE WINDS TONIGHT...NE WINDS 30 TO 4030 TO 40 KT...BECOMING N AFTER MIDNIGHT. SEAS KT...BECOMING N AFTER MIDNIGHT. SEAS

BUILDING TO 8 TO 12 FT.BUILDING TO 8 TO 12 FT.MON...N WINDS MON...N WINDS 25 TO 30 KT25 TO 30 KT. SEAS 7 TO 10 FT.. SEAS 7 TO 10 FT.

T+6hrT+6hr: Gale Warning: Gale WarningTONIGHT...NE WINDS TONIGHT...NE WINDS 30 TO 4030 TO 40 KT...WITH KT...WITH GUSTS TO 45GUSTS TO 45 KT...BECOMING N AFTER KT...BECOMING N AFTER

MIDNIGHT. SEAS 8 TO 13 FT.MIDNIGHT. SEAS 8 TO 13 FT.MON...N WINDS MON...N WINDS 30 TO 40 KT30 TO 40 KT. SEAS 9 TO 14 FT. . SEAS 9 TO 14 FT.

26 December 2004 Event26 December 2004 Event

T+12hrT+12hr: Storm Warning: Storm WarningTONIGHT...NE WINDS TONIGHT...NE WINDS 40 TO 50 KT40 TO 50 KT WITH WITH GUSTS TO 60 KTGUSTS TO 60 KT. WINDS . WINDS

BACKING TO THE N BY MORNING. SEAS 12 TO 18 FT.BACKING TO THE N BY MORNING. SEAS 12 TO 18 FT.

MON...N WINDS DIMINISHING TO MON...N WINDS DIMINISHING TO 30 TO 40 KT EARLY30 TO 40 KT EARLY...THEN ...THEN BECOMING NW 25 TO 30 KT IN THE AFTERNOON. SEAS 12 TO 18 BECOMING NW 25 TO 30 KT IN THE AFTERNOON. SEAS 12 TO 18 FT.FT.

T+16hrT+16hr: Storm Warning: Storm WarningTODAY...N TO NE WINDS TODAY...N TO NE WINDS 40 TO 50 KT40 TO 50 KT WITH WITH GUSTS TO 60 KTGUSTS TO 60 KT... ...

BECOMING NW 25 TO 35 KT LATE. SEAS BECOMING NW 25 TO 35 KT LATE. SEAS 15 TO 22 FT15 TO 22 FT..

24 hours prior to onset24 hours prior to onset

1000 hPa winds (m s-1)

Surface Analysis

12 hours prior to onset12 hours prior to onset

1000 hPa winds (m s-1)

Surface Analysis

Surface trough

analyzed

Event onsetEvent onset

Rapid wind speed increase

At this time surface winds had reached 30-40 kts sustained

Within the next 6-12 hrs surface winds reached borderline storm

force criteria

1000 hPa winds (m s-1)

Surface Analysis

Coastal Front

Event OnsetEvent Onset

850 hPa 925 hPa

1000 hPa

6 9

9 Mean wind speed over

western GoM, in m s-1

Surface winds are sustained 15-20+ ms-1…faster winds are not transported

downward

12Z Dec 26 2004 – 12Z Dec 26 2004 – KGYX SoundingKGYX Sounding

Inversion

Wind Shear

Winds at KGYX are weakerthan over coastal waters

Post-frontal Case Post-frontal Case Study:Study:

15 January 200115 January 2001

15 January 2001 Event15 January 2001 EventT-24h T-12h T-0h

15 January 2001 Event15 January 2001 Event

T-24h T-12h T-0hAlberta clipper is racing east, w/ arctic cold front

across southern Quebec

Arctic front poised across the northern mountains, weak W

wind

Northeast winds begin at all locations at this time, 15-25 G 35 kt offshore

Forecast now calls for E-NE winds 15-25 kt

overlapping two periods

Small craft advisory raised for increasing seas and

higher winds

Forecast for a period (12 hrs) of E to NE

wind, 15-25 kt

15 January 2001 Event15 January 2001 EventT-24hrT-24hr::MONDAY...E TO NE WIND 15 TO 25 KTS. AVG SEAS 2 TO 4 FT.MONDAY...E TO NE WIND 15 TO 25 KTS. AVG SEAS 2 TO 4 FT.

T-12hrT-12hr::MONDAY...E TO NE WIND 10 TO 20 KTS. AVG SEAS 2 TO 4 FT.MONDAY...E TO NE WIND 10 TO 20 KTS. AVG SEAS 2 TO 4 FT.MONDAY NIGHT...E WIND 15 TO 25 KTS. AVG SEAS 3 TO 6 FT.MONDAY NIGHT...E WIND 15 TO 25 KTS. AVG SEAS 3 TO 6 FT.

T-0hrT-0hr: : SMALL CRAFT ADVISORYSMALL CRAFT ADVISORYTODAY...NE WIND 15 TO 25 KTS WITH A FEW HIGHER GUSTS... TODAY...NE WIND 15 TO 25 KTS WITH A FEW HIGHER GUSTS...

VEERING TO THE E. AVG SEAS 3 TO 6 FT.VEERING TO THE E. AVG SEAS 3 TO 6 FT.TONIGHT...E WIND 15 TO 25 KTS WITH A FEW HIGHER GUSTS. TONIGHT...E WIND 15 TO 25 KTS WITH A FEW HIGHER GUSTS.

T+6hrT+6hr: : SMALL CRAFT ADVISORYSMALL CRAFT ADVISORYTONIGHT...E TO NE WIND 15 TO 25 KTS WITH A FEW HIGHER GUSTS. TONIGHT...E TO NE WIND 15 TO 25 KTS WITH A FEW HIGHER GUSTS.

AVG SEAS 3 TO 6 FT.AVG SEAS 3 TO 6 FT.

T+12hrT+12hr: : SMALL CRAFT ADVISORYSMALL CRAFT ADVISORYOVERNIGHT...OVERNIGHT...MERRIMACK RIVER MA TO BOOTHBAY HARBOR MEMERRIMACK RIVER MA TO BOOTHBAY HARBOR ME...N ...N

WINDS 20 TO 25 KTS...BECOMING NW. AVG SEAS 4 TO 6 FT. WINDS 20 TO 25 KTS...BECOMING NW. AVG SEAS 4 TO 6 FT. BOOTHBAY HARBOR ME TO STONINGTON MEBOOTHBAY HARBOR ME TO STONINGTON ME...E TO NE WINDS 20 ...E TO NE WINDS 20

TO 25 KTS. AVG SEAS 4 TO 6 FT. TO 25 KTS. AVG SEAS 4 TO 6 FT.

Long Lead

Time of 30 hrs for this event

Before and After Cold Frontal Before and After Cold Frontal PassagePassage

Case Study ResultsCase Study Results

Forcing for NE wind events is near-Forcing for NE wind events is near-surfacesurface– Winds aloft in the majority of events Winds aloft in the majority of events

were weakwere weak– Rules out downward momentum Rules out downward momentum

transfer argumentstransfer arguments– Mesoscale gradients and boundaries are Mesoscale gradients and boundaries are

likely the main contributorslikely the main contributors

How Predictable?How Predictable?

Most events predictable on synoptic scaleMost events predictable on synoptic scale Guidance typically signals NE flow 24-36 Guidance typically signals NE flow 24-36

hrs in advancehrs in advance– Guidance wind speed generally too low and Guidance wind speed generally too low and

attempts to ‘catch up’ as event unfoldsattempts to ‘catch up’ as event unfolds Duration of NE winds often outlasts what Duration of NE winds often outlasts what

guidance is showing…many cases guidance is showing…many cases involved NE flow as long as 12-24 hours involved NE flow as long as 12-24 hours after MOS shows a shift to E, SE, Nafter MOS shows a shift to E, SE, N

More on PredictabilityMore on Predictability Remember MOS has strong negative bias in NE Remember MOS has strong negative bias in NE

flowflow– Forecasters can hedge on the higher side…especially Forecasters can hedge on the higher side…especially

when a subtle feature (such as a coastal front, shallow when a subtle feature (such as a coastal front, shallow frontal sfc) are in playfrontal sfc) are in play

When NWP is indicating stronger NE flow…When NWP is indicating stronger NE flow…pay pay attention!attention!– Does the model solution make sense – is the model onto Does the model solution make sense – is the model onto

something, like a tightening surface pressure gradient?something, like a tightening surface pressure gradient? Subtle features do matter:Subtle features do matter:

– If a coastal zone of convergence and/or a strong thermal If a coastal zone of convergence and/or a strong thermal contrast exist, this can amplify the pressure gradient & contrast exist, this can amplify the pressure gradient & wind speed and turn the flow direction along-shore (i.e., wind speed and turn the flow direction along-shore (i.e., NE)NE)

Conceptual Model: A Plan ViewConceptual Model: A Plan View

L

H H

Low pressure develops, moves S/E of the GoM

High pressure moves S/E out of Canada

Cold front dives S/E across the region OR stnry/warm front S/E of coastal waters

High pressure builds in from Canada

Conceptual Model: A Cross-section Conceptual Model: A Cross-section ViewView

KRKD KPWM KPSM

MISM1 44007 IOSN3

NE FLOW

NW, W, SW FLOW ABOVE INVERSION

• In this case we have a coastal front/baroclinic zone trapped at the shore

• The near-surface NE flow develops seaward of the front & behind cold/warm/stnry front well offshore

• The front becomes a focus of convergence, light precip

• Coastal land-based stations report a light N-NW wind in most of these situations

Directional shearwith height across inversion sfc

SHALLOW,COLDER/ARCTIC

AIR MASS

LightN/NW flow

MODIFIED,WARMERAIR MASS

KRKD KPWM

KPSMMISM1 44007

IOSN3

NE FLOW

Coastal F

ront

(?)

• In this case we have two situations to consider, either:

a) A coastal front is along or inland of the shore, or

b) No coastal front exists

• In the first situation there is a trapped band of NE flow below inversion/front

• The second situation is dominated by a general NE flow both offshore and onshore

N, NW, W, SW FLOW ALOFT/INLAND

Conceptual Model: A Cross-section Conceptual Model: A Cross-section ViewView

Directional shearwith height across inversion sfc

COOLER,MODIFIED AIR

WARMER AIR

Current/Future WorkCurrent/Future Work

Current COMET grant focusing on the Current COMET grant focusing on the mesoscale structure of NE wind eventsmesoscale structure of NE wind events– Deriving equations to calculate gradients Deriving equations to calculate gradients

and expected flow strength based on and expected flow strength based on gradientsgradients

– These will be calculated based on model These will be calculated based on model output and real-time observationsoutput and real-time observations

NWS Gray developing GoM NE wind NWS Gray developing GoM NE wind guidance/reference for improving guidance/reference for improving situation awareness and predictabilitysituation awareness and predictability

SummarySummary

Models are biased in NE flow in the Models are biased in NE flow in the western Gulf of Mainewestern Gulf of Maine– Forecasters consequently have not Forecasters consequently have not

anticipated higher NE wind speedsanticipated higher NE wind speeds Both synoptic and mesoscale conditions Both synoptic and mesoscale conditions

important in forcing NE windimportant in forcing NE wind Situation awareness and familiarity are Situation awareness and familiarity are

keykey– Forecasters need to anticipate the Forecasters need to anticipate the

mesoscale features that can shift winds to mesoscale features that can shift winds to NE and enhance their speedsNE and enhance their speeds

AcknowledgementsAcknowledgements

Daniel MichaudDaniel Michaud– 2007 NOAA Hollings Scholar at NWS 2007 NOAA Hollings Scholar at NWS

GrayGray Dr. Sam T.K. MillerDr. Sam T.K. Miller

– Research Advisor, Professor of Research Advisor, Professor of Meteorology, Plymouth StateMeteorology, Plymouth State

A host of graduate/undergraduate A host of graduate/undergraduate PSU students who laid the PSU students who laid the groundwork for this researchgroundwork for this research

COMET Partners ProgramCOMET Partners Program NOAA Hollings Scholarship ProgramNOAA Hollings Scholarship Program